United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

General Technical

Report RMRS-GTR-42-

volume 5

December 2002

Wildland Fire in

Ecosystems

Effects of Fire on Air
Abstract _____________________________________

Sandberg, David V.; Ottmar, Roger D.; Peterson, Janice L.; Core, John. 2002. Wildland fire on

ecosystems: effects of fire on air. Gen. Tech. Rep. RMRS-GTR-42-vol. 5. Ogden, UT: U.S.

Department of Agriculture, Forest Service, Rocky Mountain Research Station. 79 p.

This state-of-knowledge review about the effects of fire on air quality can assist land, fire, and air

resource managers with fire and smoke planning, and their efforts to explain to others the science

behind fire-related program policies and practices to improve air quality. Chapter topics include air

quality regulations and fire; characterization of emissions from fire; the transport, dispersion, and

modeling of fire emissions; atmospheric and plume chemistry; air quality impacts of fire; social

consequences of air quality impacts; and recommendations for future research.

Keywords: smoke, air quality, fire effects, smoke management, prescribed fire, wildland fire, wildfire,

biomass emissions, smoke dispersion

The volumes in “The Rainbow Series” will be published through 2003. The larger bold check-mark boxes indicate the volumes

currently published. To order, check any box or boxes below, fill in the address form, and send to the mailing address listed below.

Or send your order and your address in mailing label form to one of the other listed media.

RMRS-GTR-42-vol. 1. Wildland fire in ecosystems: effects of fire on fauna.

RMRS-GTR-42-vol. 2. Wildland fire in ecosystems: effects of fire on flora.

RMRS-GTR-42-vol. 3. Wildland fire in ecosystems: effects of fire on cultural resources and archeology.

RMRS-GTR-42-vol. 4. Wildland fire in ecosystems: effects of fire on soil and water.

RMRS-GTR-42-vol. 5. Wildland fire in ecosystems: effects of fire on air.

Send to: ________________________________________________________________________________

Name

________________________________________________________________________________

Address

Fort Collins Service Center

Telephone (970) 498-1392

FAX (970) 498-1396

E-mail rschneider/rmrs@fs.fed.us

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Mailing Address Publications Distribution

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240 W. Prospect Road

Fort Collins, CO 80526-2098
Cover photo—Photo by Roger Ottmar. Smoke blots out

the sun during the 1994 Anne Wildfire in western Montana.

Wildland Fire in Ecosystems

Effects of Fire on Air

Authors

David V. Sandberg, Research Physical Scientist, Corvallis Forestry

Sciences Laboratory, Pacific Northwest Research Station, U.S. Department of Agriculture, Corvallis, OR 97331

Roger D. Ottmar, Research Forester, Seattle Forestry Sciences Laboratory, Pacific Northwest Research Station, U.S. Department of Agriculture, Seattle, WA 98103

Janice L. Peterson, Air Resource Specialist, Mt. Baker-Snoqualmie

National Forest, U.S. Department of Agriculture, Mountlake Terrace,

WA 98053

John Core, Consultant, Core Environmental Consulting, Portland, OR

97229
Preface _____________________________________

In 1978, a national workshop on fire effects in Denver, Colorado, provided the impetus

for the “Effects of Wildland Fire on Ecosystems” series. Recognizing that knowledge of

fire was needed for land management planning, state-of-the-knowledge reviews were

produced that became known as the “Rainbow Series.” The series consisted of six

publications, each with a different colored cover, describing the effects of fire on soil,

water, air, flora, fauna, and fuels.

The Rainbow Series proved popular in providing fire effects information for professionals,

students, and others. Printed supplies eventually ran out, but knowledge of fire effects

continued to grow. To meet the continuing demand for summaries of fire effects knowledge,

the interagency National Wildfire Coordinating Group asked Forest Service research leaders

to update and revise the series. To fulfill this request, a meeting for organizing the revision was

held January 4-6, 1993, in Scottsdale, Arizona. The series name was then changed to “The

Rainbow Series.” The five-volume series covers air, soil and water, fauna, flora and fuels, and

cultural resources.

The Rainbow Series emphasizes principles and processes rather than serving as a

summary of all that is known. The five volumes, taken together, provide a wealth of information

and examples to advance understanding of basic concepts regarding fire effects in the United

States and Canada. As conceptual background, they provide technical support to fire and

resource managers for carrying out interdisciplinary planning, which is essential to managing

wildlands in an ecosystem context. Planners and managers will find the series helpful in many

aspects of ecosystem-based management, but they will also need to seek out and synthesize

more detailed information to resolve specific management questions.

–– The Authors

December 2002

Acknowledgments____________________________

The Rainbow Series was compiled under the sponsorship of the Joint Fire Science Program,

a cooperative fire science effort of the U.S. Department of Agriculture, Forest Service, and the

U.S. Department of the Interior, Bureau of Indian Affairs, Bureau of Land Management, Fish

and Wildlife Service, National Park Service, and U.S. Geological Survey.

Several scientists provided significant input without requesting authorship in this volume. We

acknowledge valuable contributions by Sue A. Ferguson, Timothy E. Reinhardt, Robert

Yokelson, Dale Wade, and Gary Achtemeier. We also thank the following individuals for their

suggestions, information, and assistance that led to substantial technical and editorial

improvements in the manuscripts: Scott Goodrick, Allen R. Riebau, Sue A. Ferguson, and Patti

Hirami. Finally, we appreciate Marcia Patton-Mallory and Louise Kingsbury for persistence and

support.

ii
Contents________________________________________________

Page Page

iii

Summary ........................................................................ iv

Chapter 1: Introduction .................................................... 1

Objective ............................................................................. 2

Related Publications ........................................................... 2

Scope .................................................................................. 2

Framework .......................................................................... 2

Prior Work ........................................................................... 3

Smoke Management Guide For Prescribed

 and Wildland Fire: 2001 Edition ............................... 3

Wildland Fire and Air Quality: National Strategic

 Plan.......................................................................... 4

Introduction to Visibility ............................................... 4

The Federal Advisory Committee Act White

 Papers ..................................................................... 4

Environmental Regulation and Prescribed Fire

 Conference .............................................................. 5

Southern Forestry Smoke Management

 Guidebook ............................................................... 6

Changes in Fire Policy ........................................................ 6

Joint Fire Science Program ........................................ 6

Cohesive Strategy ...................................................... 7

National Fire Plan ....................................................... 7

Chapter 2: Air Quality Regulations and Fire .................. 9

Roles and Responsibilities Under the Clean Air Act ......... 10

National Ambient Air Quality Standards ............................ 11

Prevention of Significant Deterioration .............................. 11

Visibility ............................................................................. 12

Regional Haze .......................................................... 13

Reasonable Progress ............................................... 15

Hazardous Air Pollutants .................................................. 15

EPA Interim Air Quality Policy on Wildland and

 Prescribed Fires..................................................... 16

Natural Events Policy ........................................................ 16

Collaboration Among Stakeholders .................................. 16

Best Available Control Measures ...................................... 16

Reducing Emissions ................................................. 17

Redistributing Emissions .......................................... 17

Ozone and Fire ................................................................. 17

Chapter 3: Overview of Air Pollution from Fire ............ 19

Magnitude of Fire Contributions ........................................ 19

Smoke from Wildland Fires ...................................... 20

Smoke from Prescribed Fires ................................... 24

Impacts on National Ambient Air Quality

 Standards .............................................................. 24

Significance of Visibility Degradation ........................ 24

Greenhouse Gas Emissions from Fires .................... 24

Smoke Management Programs ........................................ 25

Chapter 4: Characterization of Emissions from

Fires ....................................................................... 27

Area Burned ...................................................................... 27

Preburn Fuel Characteristics ............................................ 28

Fire Behavior ..................................................................... 29

Combustion Stages ........................................................... 30

Fuel Consumption ............................................................. 31

Emission Factors............................................................... 32

Source Strength ................................................................ 32

Chapter 5: Transport, Dispersion, and Modeling

of Fire Emissions ................................................... 35

Basic Elements of Trajectory and Dispersion ................... 35

Heat Release ............................................................ 36

Plume Rise and Buoyancy ....................................... 36

Advection and Diffusion ............................................ 37

Scavenging ............................................................... 38

Chemical Transformations ........................................ 38

Transport and Dispersion Models ..................................... 38

Plume Models ........................................................... 38

Puff Models ............................................................... 39

Particle Models ......................................................... 39

Grid Models .............................................................. 39

Model Application .............................................................. 40

Chapter 6: Atmospheric and Plume Chemistry ........... 41

Ozone Formation in Plumes ............................................. 41

Factors Affecting Plume Chemistry ................................... 42

Emission Factors for Reactive Species ............................ 43

Particle Formation in Plumes ............................................ 43

Chapter 7: Estimating the Air Quality Impacts of

Fire ................................................................. 45

Emission Inventories ......................................................... 45

State Emission Inventories ....................................... 46

Regional Emission Inventories ................................. 46

National Emission Inventories .................................. 47

Improving Emission Inventories ................................ 47

Air Quality Monitoring ........................................................ 48

Current Monitoring Techniques ................................ 48

Source Apportionment ...................................................... 49

Source Apportionment Methods ............................... 50

Receptor-Oriented Approaches ................................ 50

Factor Analysis and Multiple Linear Regression ...... 52

Summary .................................................................. 52

Mechanistic Models .......................................................... 53

Chapter 8: Consequences of Fire on Air Quality ......... 55

Health Effects .................................................................... 55

National Review of Health Effects ............................ 55

Occupational Exposure to Wildland Fire Smoke ...... 56

Research Issues ....................................................... 57

Welfare Effects .................................................................. 58

Soiling of Materials ................................................... 58

Public Nuisance and Visibility Loss .......................... 58

Economic and Social Consequences ............................... 59

Soiling-Related Economic Losses ............................ 59

Visibility-Related Costs ............................................. 59

Highway Safety ................................................................. 60

Magnitude of the Problem ........................................ 60

Measures to Improve Highway Safety ...................... 60

Climate Change ................................................................ 61

Chapter 9: Recommendations for Future Research

and Development .................................................... 63

Established Research Framework .................................... 63

Emerging Research Needs ............................................... 65

Emissions Source Strength and Emissions

 Inventory ................................................................ 65

Ambient Air Quality Impacts ..................................... 66

Effects on Receptors ................................................ 66

Conclusion ........................................................................ 67

References ........................................................................ 69
Summary

Wildland fire is an integral part of ecosystem management and is essential in maintaining functional ecosystems, but air pollutants emitted from those fires can be

harmful to human health and welfare. Because of the

public and governmental concerns about the possible

risk of wildland fire smoke to public health and safety, as

well as nuisance, visibility, ozone generation, and regional haze impacts, increasingly effective smoke management programs and air quality policies are being

implemented with support from research and land management agency programs.

This state-of-knowledge review of what is known about

the effects of fire on air quality has been prepared to

assist those in the fire and air quality management

communities for future discussion of management, policy,

and science options for managing fire and air quality. The

introduction sets up a framework in which to discuss the

interaction between pollutants emitted from fire, and air

quality at the national, State, and local levels applied to

air resource management, fire management, and geographical scale components. It also provides an overview of science reviews conducted since 1979 and

discusses recent changes in fire policy, strategies, and

funding. The Clean Air Act and its amendments are

discussed in chapter 2, in the context of how and why fire

impacts each issue, what information is needed, and who

needs it to fulfill legal requirements under the act. National ambient air quality standards, regional haze and

visibility, hazardous air pollutants, and best available

control methods are some of the topics covered. Chapter

3 covers the magnitude of the impacts of prescribed and

wildland fire on air quality, and contains an overview of

smoke management plans intended to manage those

impacts.

Chapters 4 through 7 present scientific and technical

discussions. Chapter 4 discusses the characterization

and production rate of emissions from fire in terms of

fuels, fire behavior, stages of combustion, fuel consumption, and emission factors of various pollutants. The basic

elements and modeling of transport and dispersion are

covered in chapter 5, including, plume, puff, particle, and

grid models. Chapter 6 considers plume and atmospheric chemistry, the chemical reactions that occur in

plumes, with a focus on ozone formation and particle

formation. Use of emission inventories, air quality monitoring, and source apportionment methods, and mechanistic models to estimate the impacts of fire on air quality

are covered in chapter 7. Chapter 8 reviews the health,

welfare, economic, and safety consequences of these

impacts. The final chapter recommends priorities for

future research to better understand and quantify fire and

its effect on air quality.

iv

Metric Equivalents

When you know: Divide by: To find:

Feet (ft) 3.28 Meters

Pounds (lb) 2.21 Kilograms

Acres 2.47 Hectares

Pounds per acre 0.89 Kilograms per

 hectare

Fahrenheit (°F) 1.8 and subtract 32 Celsius
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 1

Chapter 1:

Introduction

A state-of-knowledge review, Effects of Fire on Air,

was written in 1979 to inform environmental agencies, fire managers, and land management planners,

and to guide research strategies in the intervening

years (Sandberg and others 1979). That review is still

technically sound for the most part, but substantial

new knowledge is now available. In this volume, we

update that review of knowledge important for managing the effects of fire on air and for adjusting the

course of new research. In addition, we expand the

scope of our review to place the information in the

context of new policies regarding fire management

and air quality management

Acquisition of scientific knowledge regarding air

pollution from fires is motivated by active policy development both to restore the role of fire in ecosystems

and to improve air quality. Land managers require

quantitative analysis and goal-seeking solutions to

minimize the negative consequences of fire management. Managing fire and air quality to the standards

set by Congress requires an increasingly detailed base

of scientific knowledge and information systems.

The Federal Wildland Fire Policy (U.S. Department of

the Interior and U.S. Department of Agriculture 1995)

and the Clean Air Act as Amended 1990 (PL 101-549)

resulted in the need to significantly raise the level of

knowledge about fire’s effects on air in order to meet

regulatory and management requirements. For example,

new information is needed to assess, monitor, predict,

and manage:

• Emissions and air quality impacts from wildfires

• Acute health effects of human exposure to

smoke

• Natural and anthropogenic sources of visibility reduction

• Cumulative air quality impacts from expanded

fuel management programs

• Tradeoffs between air quality impacts from

wildland fire and prescribed fire

Likewise, management of fire and air quality is also

undergoing substantial policy development that has

led to the need for new and different information to

satisfy regulatory and management requirements. As

both legal and management issues mature, there is

less a sense that environmental regulation is a limitation on fire management, and more of a sense that

ecosystem management goals, fire safety, and air

quality are goals to be met collectively. For example,

new air quality rules recognize the importance of the

role of fire in sustaining ecosystems and the inherent

tradeoffs between prescribed fire and wildland fire

occurrence. At the same time, land management plans

and real-time fire management decisions increasingly

factor in the expected consequences to air quality.
2 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Since 1995, researchers and land managers have

concentrated a great deal of energy to extend what is

known about fire and its effect on air quality; to expand

information systems that make knowledge readily

available to policy, management, and public clients; to

merge what is known about sustainable ecosystems

and disturbance ecology with what is known about the

chemistry, physics, biology, and social impacts of air

pollution; and to redefine the research agenda.

Objective ______________________

This review summarizes the current state of knowledge of the effects of fire on air, and defines research

questions of high priority for the management of

smoke from fires. We also intend this as a reference

document for future discussion of management, policy,

and science options for managing fires and air quality.

This review is limited to readily available published

and unpublished knowledge and to original contributions by the authors. No new analysis of data or policy,

nor assessment of impacts and options, is included

herein.

Related Publications _____________

This document does not stand alone. There are

several excellent sources for information on the effects

of fire on air. We advise the reader to include at least

the following publications, each of which will be abstracted in this document, in your reference library:

• Smoke Management Guide for Prescribed and

Wildland Fire: 2001 Edition (Hardy and others 2001)

• National Strategic Plan: Modeling and Data

Systems for Wildland Fire and Air Quality

(Sandberg and others 1999)

• Introduction to Visibility (Malm 2000)

• Fire Effects on Air (Sandberg and others 1979)

• Southern Forestry Smoke Management Guidebook (Southern Forest Fire Laboratory Personnel 1976)

• Development of Emissions Inventory Methods

for Wildland Fire (Battye and Battye 2002)

Why, then, is another state-of-knowledge review

necessary on the subject of fire effects on air? First,

because policy and regulatory development in air

quality management and in fire management is advancing rapidly, and there is a continuing need to

reassess current knowledge about what is required to

meet new expectations. Second, this document addresses the advancement of science at a much higher

level than the above-mentioned references. Third,

because the Joint Fire Science Program has sponsored

a series of reviews, nicknamed the Rainbow Series (see

“Preface”), to compile a broad reference of fire effects

to serve practitioners and policymakers charged with

using and managing fire, and this is the third volume

in that series. Finally, we hope you will find this

volume a useful attempt to abstract and fill in the gaps

left by the previous publications.

Scope _________________________

This review includes all health and welfare effects of

air pollution from fires, but does not include the effects

of air resource management on ecosystem health or

any other value. Unless otherwise specifically stated,

the term “fires” in this manuscript includes all prescribed and wildland fires on wildlands. Prescribed

fires are ignited intentionally to achieve ecosystem

management or fire protection objectives, whereas

wildland fires result from unplanned ignitions on

wildlands. Wildlands include all the nonagricultural

and nonresidential rural lands of the United States,

including the wildland-urban interface, regardless of

ownership, sovereignty, or management objective.

Management response to wildland fires differs greatly

according to economic efficiency, the values at risk

(including air quality), and the expected ecological

consequences. Wildfires are at one end of the spectrum

of wildland fires in that they are unwanted and unplanned, and are managed to minimize cost plus loss.

At the other end of the spectrum are wildland fires

that benefit ecosystem values, and are managed to

maximize their benefit. Ideally, each wildland fire is

evaluated with respect to expected costs, losses, risks,

and benefits in order to provide an appropriate and

preplanned response. Because fires are a significant

emitter of air pollutants, many other fire management

activities such as fire prevention or fuel treatment

may have an indirect effect on air quality.

Framework _____________________

The issues, responsibilities, and tools that address

fire and air quality are varied and complex, sometimes

resulting in confusion about the physical scale and

temporal stage of three characteristics: the application to fire management, the application to air resource management, and the physical process of air

pollution. National Strategic Plan: Modeling and Data

Systems for Wildland Fire and Air Quality (Sandberg

and others 1999) provides a conceptual framework for

visualizing fire’s effects on air by representing the

scope of the problem as a three dimensional array of

air resource management, fire management, and scale

components (fig. 1-1). The air resource component is

ordered in time from emissions source strength, to

ambient air quality, and to effects. The fire management component includes planning, operations, and
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 3

monitoring. The scale component includes the event,

landscape, state or tribal, and regional scales.

We have organized this volume around the air resource component and expanded it to include a regulatory perspective (fig. 1-2). Fire in the context of the

regulatory environment is the subject of chapters 2

and 3. Biomass consumption and emissions are the

subject of chapter 4; transport and dispersion of pollutants in the atmosphere the subjects of chapters 5 and

6; air quality impacts the subject of chapter 7; and the

effect on human values from exposure to air pollutants

the subject of chapter 8. We conclude with a review of

recommendations for future research in chapter 9.

Prior Work _____________________

Since the publication of Effects of Fire on Air

(Sandberg and others 1979), significant changes have

come to pass in both the technical and policy issues

that surround the fire and air quality dilemma. The

conferences, stakeholder group discussions, and technical publications discussed here have helped to shape

the current fire management programs and will influence future programs.

Smoke Management Guide For Prescribed

and Wildland Fire: 2001 Edition

Smoke Management Guide for Prescribed and Wildland Fire: 2001 Edition (Hardy and others 2001) has

been developed by the Fire Use Working Team of the

National Wildfire Coordinating Group (NWCG) and

involves most of the same authors as this current

publication. The guide provides fire management

and smoke management practitioners with a fundamental understanding of fire emissions processes

and impacts, regulatory objectives, and tools for the

management of smoke from fires. It is a comprehenFigure 1-1—Three primary components of the issues, responsibilities, and tools related to wildland fire and air quality: air

resource management, fire management, and scale (Sandberg

and others 1999).

Figure 1-2—The relations of air regulations and physical processes to the three categories within the air

resource component. OSHA/NIOSH = Occupational Safety and Health Administration/National Institute for

Occupational Safety and Health (Sandberg and others 1999).
4 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

sive treatment of the state of knowledge regarding

fire and air quality and provides guidance to practitioners. We will not attempt to duplicate its level of

detail in this volume. Rather, we add some technical

background and analysis of research needs relative

to new requirements for management.

First published in 1985, the guide is intended to

provide national guidance for the planning and managing of smoke from prescribed fires to achieve air

quality requirements through better smoke management practices (NWCG 1985). This guide has been

widely distributed within the fire community and air

quality regulatory agencies, and to private and Tribal

land managers, providing a single comprehensive

source of information on fire and air quality issues.

Much has changed since 1985 in prescribed burning

practices, smoke management programs, and air quality regulatory requirements. These changes are reflected in the 2001 edition of the guide, which includes

expanded sections on fire and emissions processes,

smoke impacts on health, welfare, safety, and nuisance; regulations for smoke management; and the

fundamentals of responsible smoke management

(Hardy and others 2001). These fundamentals include

fire planning, use of smoke management meteorology,

techniques to reduce emissions, smoke dispersion prediction systems, air quality monitoring methods, and

program assessment.

The most significant change in the guide is the

expanded and updated section on techniques to reduce

emissions and impacts. While the 1985 guide focused

primarily on minimizing smoke impacts by meteorological scheduling and dispersion, the 2001 guide

provides detailed information on emissions reduction

techniques, used in different regions of the country,

that have been useful, practicable, and effective in the

field. This emphasis on actual reduction of emissions

rather than dispersion was provided in response to air

quality regulations that now target regional emissions

reductions.

Readers will also find that the 2001 guide has a great

deal more information on the latest developments in

national air quality regulations that affect fire programs including the regional haze and visibility protection programs, Clean Air Act’s conformity requirements, EPA’s Interim Air Quality Policy on Wildland

and Prescribed Fires (EPA 1998), and NEPA planning

guidance. The guide was drafted by 16 authors and

five editor/compilers working under the sponsorship

of the NWCG Fire Use Working Team with support

from the EPA.

Wildland Fire and Air Quality: National

Strategic Plan

Another recent publication also provides a systematic review of the state of knowledge and information

systems. This strategic plan was also sponsored by

the NWCG and the Environmental Protection Agency

(EPA).

In 1997, the NWCG Fire Use Working Team sanctioned a small group of fire research scientists and air

quality managers to develop a National Strategic

Plan: Modeling and Data Systems for Wildland Fire

and Air Quality (Sandberg and others 1999) to foster

development and implementation of models and data

systems that could be used to manage air quality

impacts of fires. The resulting report provides a conceptual design and strategic direction toward meeting

the increasing need for information required to manage emissions from fire (Sandberg and others 1999). In

November 1997, after 2 years of drafting and extensive review of a draft plan, 86 experts attended a

national workshop, and using the discussion framework presented in this chapter, they defined the current state of knowledge, desired future condition, and

recommendations for research and development for

each cell in the discussion framework.

The strategic plan targets a more technical, scientific, and policy-oriented audience than the smoke

management guide, and recommends a research and

development strategy to reach a desired future state

for smoke management information systems. It also

provides a comprehensive treatment of policy and

technical issues that we will not duplicate in this

volume.

Introduction to Visibility

Air pollution impacts on visibility are discussed in

detail in Introduction to Visibility (Malm 2000). The

discussion is not specific to the impacts of fire but is

relevant because of the regulatory attention given to

fire in the EPA Regional Haze Rule (40 CFR Part 51

1999) and because Federal land managers have the

responsibility of managing fires and the impacts of

fires and all other pollution sources on visibility in

many National Parks and wilderness areas. We make

no attempt in this volume to duplicate this discussion

of the atmospheric physics, meteorology, historic visibility trends, monitoring and apportionment methodologies, or human perceptions that are so admirably

covered in Introduction to Visibility.

The Federal Advisory Committee Act

White Papers

During the 1997 to 1998 development of proposed

national ambient air quality standards (NAAQS) for

PM2.5 (particulate matter with an aerodynamic diameter less than or equal to 2.5 microns) and regional haze

regulations, EPA used provisions of the Federal Advisory Committee Act (FACA) to convene a large group of

stakeholders who were interested in providing input to
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 5

the regulatory process. A FACA committee for the

development of ozone, particulate matter, and regional

haze implementation programs was formed to address

both policy and technical issues. The committee’s Science and Technology Wildland Fire Issues Group, one

of several working groups and subcommittees, researched and drafted five reports that are briefly summarized below (EPA 2000c).

Air Monitoring for Wildland Fire Operations provides recommendations for conducting air-monitoring

programs designed to support fire activities that also

monitor for compliance with NAAQS. It also describes

how monitoring can support burning programs and

how land managers can collaborate with air agencies,

and it provides guidance for selecting monitoring

equipment.

Elements of a Smoke Management Program discusses recommendations for a basic level smoke management program. The document summarized information from an EPA-sponsored workshop held to

respond to specific questions posed by EPA. The document describes the six basic components of a smoke

management program:

• Authorization to burn

• Minimizing emissions

• Burn plan components

• Public education

• Surveillance and enforcement

• Program evaluation

It also provides examples of monitoring methods,

public awareness programs, and program enforcement.

Emission Inventories for State Implementation Plan

[SIP] Development describes several levels of inventory complexity: a default level based on currently

available information; a basic level program that is

considered the minimal program needed to support

SIP development; and a detailed inventory level when

a greater level of analysis or accountability in inventory precision is needed. Elements of each level of

inventory are described, data sources are identified

and data management issues are discussed.

What Wildland Fire Conditions Minimize Emissions and Hazardous Air Pollutants and Can Land

Management Goals Still be Met? This paper is a discussion of fire conditions and techniques that minimize pollutant emissions. Both wildland emissions

and prescribed fire emissions are discussed. The discussion of emissions reduction techniques for prescribed burning is also found in Smoke Management

Guide for Prescribed and Wildland Fire: 2001 edition

(Hardy and others 2001).

Estimating Natural Emissions from Wildland and

Prescribed Fire addresses how best to define “natural

emissions” from fire. This is critical to implementing

regional haze goals of reducing visibility degradation

caused by human-made sources of air pollution. The

paper discusses a matrix of choices: (1) emissions from

fire necessary to restore and sustain desired ecosystem characteristics, (2) fire needed to manage fuels to

a condition where they can be dealt with most effectively from a wildfire control standpoint, (3) no net

increase in fire emissions, and (4) no change from

current emissions.

Stakeholders reviewed, discussed, and drafted, additional work on these five reports. The reports and

other technical references were considered by EPA

during the formulation of the regional haze regulations and revisions to the particulate matter NAAQS.

Environmental Regulation and Prescribed

Fire Conference

In March 1995 a conference on new developments in

environmental regulations related to prescribed fire

was held in Tampa, FL (Conference Proceedings: Environmental Regulation & Prescribed Fire: Legal and

Social Challenges, Bryan 1997). This 3-day meeting

included sessions on challenges and strategies regarding the use of fire, air quality regulation, and liability,

as well as social and economic issues. Sponsored by

numerous State and Federal environmental and forestry agencies, the conference provided a forum for

discussion of the Clean Air Act, Endangered Species

Act, and other Federal statutes that guide national,

State, and local regulations pertaining to prescribed

fire.

Significantly, a joint declaration drafted by the conference steering committee and presented to conference attendees was later signed by representatives of

the EPA, State of Florida, National Biological Survey,

The Wilderness Society, Forest Service, and Mariposa

County, Florida. In summary, the declaration upheld

the following principles:

• Practitioner liability is a major obstacle to the

increased use of fire. Legislation should be

considered on the Federal level to protect

properly certified fire practitioners except in

cases where negligence is proven.

• Partnerships among all of the stakeholders

are vital to the future use of fire. Efforts to

enhance such partnerships must be encouraged especially in the exchange of information, development of best management practices, public education campaigns, and funding

initiatives.

• Agencies should work together to evaluate

tradeoffs between public health risks from

fire and ecological damage caused by fire

exclusion.
6 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

• Public education regarding the use of prescribed fire, ecosystem health, and risks of

wildfire versus those from prescribed burning

is encouraged.

• The role of fire in ecosystem management

needs to be understood by all stakeholders.

The ramifications of not using prescribed fire

are serious and must also be appreciated as

limits on fire use may conflict with other

public mandates.

• Actions pertaining to the use of fire must be

based on sound science. There are several

crucial knowledge gaps that must be filled.

Consequences to public safety caused by delaying the increases of prescribed fire are

great.

• Public and private property owners need to

retain the right to use prescribed fire to protect and enhance the productivity of their

lands while also protecting nearby property

owners from adverse impacts of burning.

• Administrators responsible for allocating funds

should do so on the basis of regional priorities

with greater emphasis on prevention than in

the past.

• An increased emphasis on training for prescribed fire practitioners is needed to enhance

public acceptance.

Southern Forestry Smoke Management

Guidebook

The Southern Forestry Smoke Management Guidebook(Southern Forest Fire Laboratory Personnel 1976)

was one of the first smoke management guidebooks

developed in the United States for use by land, fire,

and air resources managers. The guide provides an

improved understanding of: (1) smoke management

and air quality regulations; (2) contents of smoke and

variables affecting production; (3) smoke transport

and dispersion; (4) potential effects on human health,

human welfare, and visibility; and (5) what can be

done to mitigate its impacts. A system for predicting

and modifying smoke concentrations from prescribed

fires was introduced for Southern fuels.

Changes in Fire Policy ___________

The Federal Wildland Fire Policy (USDI and USDA

1995; USDI and others 2001) requires that “... fire, as

a critical natural process, must be reintroduced into

the ecosystem to restore and maintain sustainable

ecosystems. This will be accomplished across agency

boundaries and will be based on the best available

science.” The policy requires “the use of fire to sustain

ecosystem health based on sound scientific principles

and balanced with other social goals including public

health and safety, air quality, and other specific environmental concerns.” Early in the planning process,

action is required to “involve public health and environmental regulators in developing the most workable

application of policies and regulations.” Agencies are

called on to “create a system for coordination and

cooperation among land managers and regulators

that explores options within existing laws to allow for

the use of fire to achieve goals of ecosystem health

while protecting individual components of the environment, human health, and safety.” The policy also

requires that air quality values be considered during

preparedness and fire protection. When setting protection priorities, land managers must “define values

to be protected working in cooperation with state,

local, and tribal governments, permittees, and public

users. Criteria will include environmental, commodity, social, economic, political, public health, and other

values.”

Several strategies and funding programs were developed to improve the ability of managers to fully

implement this policy.

Joint Fire Science Program

The Joint Fire Science Program (JFSP) was created

by Congress in the 1998 Appropriations to Interior

and Related Agencies bill to augment the delivery of

science and information systems necessary to manage

the increased use of fire and other fuel treatments. The

legislation provides a mandate to protect air quality in

conjunction with economic efficiency and ecological

consequences. The program (National Interagency

Fire Center 2002 unpaginated) recognizes that:

Land managers are rapidly expanding the use of fire

for managing ecosystems while air resource managers

are accelerating efforts to reduce the local and regional

impacts of smoke. Smoke management (meeting air

quality standards) is a legal requirement of the Clean

Air Act, as well as a health and safety issue for the

general populace and fireline personnel. The JFSP will

attempt to define these social relationships and develop analytical tools and communication practices to

help mangers include social considerations in decision

making.

One of the goals of the JFSP is “to evaluate various

treatment techniques for cost effectiveness, ecological

consequences, and air quality impacts.” The program

plan states:

Methods have not been developed to assess the opportunities, costs, and effectiveness of employing smoke

reduction techniques throughout the country. Current

models to assess regional scale cumulative effects on

air quality and water quality will need to be expanded.

The program will develop a nationally consistent system of models for fuel consumption, emissions production, and smoke dispersal that can assess cumulative
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 7

effect. This research would also contribute to understanding the potential national and global impacts of

changes in biomass use, prescribed fire, and wildland

fire on wood supply, atmospheric chemistry, and carbon sequestration.

Cohesive Strategy

Protecting People and Sustaining Resources in FireAdapted Ecosystems: A Cohesive Strategy (Laverty

and Williams 2000) is the Federal framework established to restore and maintain ecosystem health to

reduce the threat and consequences of wildfires. It is

presumed that fire suppression over the past 100

years has excluded fire from many ecosystems, fueling

conditions for unnaturally intense fires that, among

other effects, threaten air quality. Citing serious air

quality impacts from long duration wildfire episodes

in recent years, the report expresses concern that:

The extent to which management for ecosystem resilience can improve air quality over the long term is not

completely known. Present regulatory policies measure

prescribed fire emissions, but not wildland fire emissions. The emissions policy tends to constrain treatments and – in short interval fire systems — may act to

inadvertently compound wildland fire risks. (p 34)

The cohesive strategy directs land management

agencies to collaborate with the EPA in addressing

long-term impacts, tradeoffs, and issues regarding air

quality and other impacts. The report acknowledges

that programmatic analysis of air quality impacts will

be a necessary step in implementing the planned

increases in prescribed burning necessary to restore

the health of fire-prone ecosystems. The strategy estimates that the USDA Forest Service Regions would

increase fuel treatments by five-fold in the West and

two-fold in the East and South to achieve restoration

goals within 10 years; or employ a slightly smaller

increase to obtain results in 20 years. Most, but not all,

of the treatments would involve burning.

The relative risk to air quality was projected to

decrease by about 25 percent as a result of improving

the resilience of ecosystems, according to current

models.

The cohesive strategy is responsive to regulatory

responsibilities. The planned increase in burning is

constrained in part by the consideration to regulatory

obligations, with an acknowledgment that a more

rigorous assessment of impacts could substantially

change the planned extent and schedule of treatments. Concerns for public health issues and firefighter

safety in relation to smoke are also expressed. The

strategy acknowledges that air quality issues must be

analyzed more thoroughly at smaller scales as it is

stepped down to landscape and project level planning.

National Fire Plan

The National Fire Plan was established in A Report

to the President In Response to the Wildfires of 2000

(USDA and USDI 2000), and implemented using Collaborative Approach for Reducing Wildfire Risks to

Communities and the Environment: 10-Year Comprehensive Strategy(Western Governors’ Association 2001).

Stakeholder groups under the sponsorship of the USDA

Forest Service, USDI, and the Western Governors’

Association prepared the implementation strategy.

This strategy recognizes that key decisions in setting

priorities for restoration, fire, and fuel management

should be made at local levels. As such, the plan

requires an ongoing process whereby the local, Tribal,

State and Federal land management, scientific, and

regulatory agencies exchange the required technical

information, including the assessment of air quality

tradeoffs, to inform this decisionmaking process. The

strategy has a goal of maintaining and enhancing

community health and economic and social well-being; and requires that public health risks from smoke

are reduced, airshed visibility is improved, and smoke

management plans are developed in conjunction with

prescribed fire planning and implementation.
8 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Notes

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 9

This chapter introduces the regulatory environment

for smoke from prescribed and wildland fire, providing

updated discussion of the laws, regulations, standards, and regulatory strategies that have changed

since about 1980. We explain roles and responsibilities of the regulatory agencies and land managers, and

we frame the technical discussion in the context of who

needs what information to fulfill legal requirements.

Air pollution is the presence in the atmosphere of

one or more contaminants of a nature, concentration,

and duration to be hazardous to human health or

welfare (Sandberg and others 1999). Welfare includes

potential to harm animal or ecosystem health, economic activity, or the comfortable enjoyment of life

and property. Air pollution is created from both human (that is, anthropogenic) and natural sources.

Anthropogenic air pollution is the presence in the

atmosphere of a substance or substances added directly or indirectly by a human act, in such amounts as

to adversely affect humans, animals, vegetation, or

materials (Williamson 1973). Air pollutants are classified into two major categories: primary and secondary. Air pollutant emissions, or simply “emissions,”

are the production and release of air contaminants

emitted from fires that have a potential to cause air

pollution. This definition includes particulates, hydrocarbons, carbon monoxide (CO), metals, and all other

Chapter 2: Air Quality

Regulations and Fire

trace gases that may be hazardous or that are chemical precursors to secondary air pollution. Primary

pollutants are those directly emitted into the air.

Under certain conditions, primary pollutants undergo

chemical reactions within the atmosphere and produce new substances known as secondary pollutants.

Hazardous air pollutants are a special class of air

pollutants identified in the Clean Air Act Amendments of 1990 as constituting a hazard to human

health.

Air quality is a measure of the presence of air

pollution. Ambient air quality is defined by the Clean

Air Act of 1963 as the air quality anywhere people have

access, outside of industrial site boundaries. Ambient

air quality standards are standards of air quality

designed to protect human health or welfare. Air

resource management includes any activity to anticipate, regulate, or monitor air pollution, air pollutant

emissions, ambient air quality, or the effects of air

pollution resulting from fires or fire management.

In the past, emissions from prescribed fire were

considered human-caused, and wildland fires were

considered natural sources of emissions. But recent

policy debate has focused on what should be considered natural; that is, to be reasonably unaffected by

human influence. This debate resulted from the

paradox that not all wildland fires are vigorously
10 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

suppressed and that some prescribed burning is

done to maintain healthy natural ecosystems where

fire has previously been excluded.

Air resource management includes any activity to

anticipate, regulate, or monitor air pollution, air pollutant emissions, ambient air quality, or the effects of

air pollution resulting from fires or fire management.

Emissions and impacts on air quality from fires are

managed and regulated through a complex web of

interrelated laws and regulations. The primary legal

basis for air quality regulation across the nation is the

Federal Clean Air Act (CAA), which is actually a series

of acts, amendments, and regulations that include:

• Federal Air Pollution Control Act of 1955 (PL

84-159). Provides for research and technical

assistance and authorizes the Secretary of

Health, Education, and Welfare to work toward a better understanding of the causes and

effects of air pollution.

• Federal Clean Air Act of 1963 (PL 88-206).

Empowers the Secretary of Health, Education, and Welfare to define air quality criteria

based on scientific studies. Provides grants to

state and local air pollution control agencies.

• Federal Air Quality Act of 1967 (PL 90-148).

Establishes a framework for defining “air quality control regions” based on meteorological

and topographical factors of air pollution.

• Federal Clean Air Act Amendments of 1970

(PL 91-604). Principal source of statutory authority for controlling air pollution. Establishes basic U.S. program for controlling air

pollution.

• Environmental Protection Agency (EPA) promulgates national ambient air quality standards (NAAQS) for particulates, photochemical oxidants (including ozone), hydrocarbons,

carbon monoxide, nitrogen dioxide, and sulfur

dioxide (1971).

• Clean Air Act Amendments of 1977 (PL 95-

95). Sets the goal for visibility protection

and improvement in Class I areas and assigns Federal land managers the affirmative responsibility to protect air quality related values.

• Clean Air Act Amendments of 1990 (PL 101-

549). Establishes authority for regulating regional haze and acknowledges the complexity

of the relation between prescribed and wildland fires.

• Regional Haze Regulations, Final Rule (40

CFR Part 51) (1999). EPA promulgates the

Regional Haze Rule supported in part by the

1998 Interim Air Quality Policy on Wildland

and Prescribed Fires.

Roles and Responsibilities Under

the Clean Air Act ________________

States have the lead in carrying out provisions of the

Clean Air Act because appropriate and effective design of pollution control programs requires an understanding of local industries, geography, transportation, meteorology, urban and industrial development

patterns, and priorities. The EPA has the task of

setting air quality standards (national ambient air

quality standards, or NAAQS). In addition, EPA develops policy and technical guidance describing how

various Clean Air Act programs should function and

what they should accomplish. States develop State

implementation plans (SIPs) that define and describe

customized programs they will implement to meet

requirements of the Clean Air Act. Tribal lands are

legally equivalent to State lands, and Tribes prepare

Tribal implementation plans (TIPs) to describe how

they will implement the Clean Air Act. Individual

States and Tribes can require more stringent air

quality standards but cannot weaken clean air goals

set by EPA.

Federal land managers have the complex role of

managing a fire as a source of air pollutants, while

fulfilling monitoring and regulatory responsibilities

tied to visibility and regional haze. Federal land

managers are given the responsibility by the Clean

Air Act for reviewing prevention of significant deterioration (PSD) permits (discussed later in this chapter) of major new and modified stationary pollution

sources and commenting to the State on whether

there is concern for visibility impacts (or other resource values) in Class I areas downwind of the

proposed pollution source. Some States require modeling of source impacts on Class I areas, and Federal

land managers customarily comment on the model

results.

The 1990 Clean Air Act Amendments require

planned Federal actions to conform to SIPs. This

“general conformity rule” prohibits Federal agencies

from taking any action within a nonattainment or

maintenance area that (1) causes or contributes to a

new violation of air quality standards, (2) increases

the frequency or severity of an existing violation, or

(3) delays the timely attainment of a standard as

defined in the applicable SIP or area plan. The general conformity rule covers direct and indirect emissions of criteria pollutants, or their precursors, which

are caused by a Federal action, are reasonably

foreseeable, and can practicably be controlled by

the Federal agency through its continuing program

responsibility.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 11

National Ambient Air Quality

Standards______________________

The purpose of the Clean Air Act is to protect

humans against negative health or welfare effects

from air pollution. National ambient air quality standards (NAAQS) are defined in the Clean Air Act as

amounts of pollutant above which detrimental effects

to public health or welfare may result. NAAQS have

been established for the following criteria pollutants:

particulate matter (PM10 and PM2.5; NAAQS for

particulate matter are established for two aerodynamic diameter classes: PM10 is particulate matter

less than 10 microns in diameter, and PM2.5 is less

than 2.5 microns in diameter; total suspended particulate matter is called PM or sometimes TSP), sulfur

dioxide (SO2), nitrogen dioxide (NO2), ozone, carbon

monoxide (CO) and lead (Pb) (table 2-1). Primary

NAAQS are set at levels to protect human health;

secondary NAAQS are to protect human welfare effects including visibility as well as plant and materials

damage.

An area that is found to be in violation of a primary

NAAQS is labeled a nonattainment area (fig. 2-1); an

area once in nonattainment but recently meeting

NAAQS, and with appropriate planning documents

approved by EPA, is a maintenance area; all other

areas are attainment or unclassified (due to lack of

monitoring). State air quality agencies can provide

up-to-date locations of local nonattainment areas

(PM2.5 is a newly regulated pollutant, so attainment/

nonattainment status had not been determined at the

time of publication of this document; monitoring must

take place for at least 3 years before designation can be

made, which means PM2.5 status will likely not be

known until at least 2003). States are required through

their SIPs to define programs for implementation,

maintenance, and enforcement of the NAAQS within

their boundaries. Wildland fire in and near

nonattainment areas will be scrutinized to a greater

degree than in attainment areas and may be subject to

general conformity rules. Extra planning, documentation, and careful scheduling of prescribed fires will

likely be required to minimize smoke effects in the

nonattainment area to the greatest extent possible. In

some cases, the use of fire may not be possible if

significant impacts to a nonattainment area are likely.

The major pollutant of concern in smoke from fire is

fine particulate matter, both PM10 and PM2.5. Studies indicate that 90 percent of all smoke particles

emitted during wildland burning are PM10, and 90

percent of PM10 is PM2.5 (Ward and Hardy 1991). The

most recent human health studies on the effects of

particulate matter indicate that fine particles, especially PM2.5, are largely responsible for health effects

including mortality, exacerbation of chronic disease,

and increased hospital admissions (Dockery and others 1993; Schwartz and others 1996).

Prevention of Significant

Deterioration ___________________

Another provision of the Clean Air Act with some

applicability to wildland burning activities is the prevention of significant deterioration (PSD) provisions.

Table 2-1—National ambient air quality standards (NAAQS) (U.S. Environmental Protection

Agency 2000b). Primary NAAQS are set at levels to protect human health;

secondary NAAQS are to protect human welfare.

Pollutant Averaging time Primary Secondary

PM10 Annual arithmetic mean 50 μg/m3 a 50 μg/m3

24-hour average 150 μg/m3 150 μg/m3

PM2.5 Annual arithmetic mean 15 μg/m3 15 μg/m3

24-hour average 65 μg/m3 65 μg/m3

Sulfur dioxide (SO2) Annual average 0.03 ppmb —

24-hour average 0.14 ppm —

3-hour average — 0.50 ppm

Carbon monoxide (CO) 8-hour average 9 ppm —

1-hour average 35 ppm —

Ozone (O3) 8-hour average 0.12 ppm 0.12 ppm

1-hour average 0.08 ppm 0.08 ppm

Nitrogen dioxide (NO2) Annual average 0.053 ppm 0.053 ppm

Lead (Pb) Quarterly average 1.5 μg/m3 1.5 μg/m3

a

μg/m3 = micrograms per cubic meter. b

ppm = parts per million.
12 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

The goal of PSD is to prevent areas that are currently

cleaner than is allowed by the NAAQS from being

polluted up to the maximum ceiling established by the

NAAQS. Three air quality classes were established by

the Clean Air Act PSD provisions including Class I

(which allows very little additional pollution), Class II

(which allows some incremental increase in pollution),

and Class III (which allows pollution to increase up to

the NAAQS). Class I areas include wildernesses and

national memorial parks over 5,000 acres, National

Parks exceeding 6,000 acres, and all international

parks that were in existence on August 7, 1977, as well

as later expansions to these areas (fig. 2-2).

Historically, EPA has regarded smoke from wildland fires as temporary and therefore not subject to

issuance of a PSD permit; whether or not wildland

fire smoke should be considered when calculating

PSD increment consumption or PSD baseline was not

defined. EPA recently reaffirmed that States could

exclude prescribed fire emissions from increment

analyses provided the exclusion does not result in

permanent or long-term air quality deterioration

(EPA 1998). States are also expected to consider the

extent to which a particular type of burning activity

is truly temporary, as opposed to an activity that

could be expected to occur in a particular area with

some regularity over a long period. Oregon is the only

State that has chosen to include prescribed fire emissions in PSD increment and baseline calculations.

Visibility _______________________

The 1977 amendments to the Clean Air Act include

a national goal of “the prevention of any future, and

the remedying of any existing, impairment of visibility

Figure 2-1—PM10 nonattainment areas as of May 2002. Current nonattainment status for PM10 and all other criteria

pollutants are available from the Environmental Protection Agency (EPA) aerometric information retrieval system

(AIRS) Web page at http://www.epa.gov/air/data/index.html (EPA 2002).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 13

in mandatory Class I Federal areas which impairment

results from manmade air pollution” (42 U.S.C §

7491). States are required to develop implementation

plans that make “reasonable progress” toward the

national visibility goal.

Atmospheric visibility is affected by scattering and

absorption of light by particles and gases. Particles

and gases in the air can obscure the clarity, color,

texture, and form of what we see. Fine particles most

responsible for visibility impairment are sulfates, nitrates, organic compounds, elemental carbon (or soot),

and soil dust. Sulfates, nitrates, organic carbon, and

soil tend to scatter light, whereas elemental carbon

tends to absorb light. Fine particles (PM2.5) are more

efficient per unit mass than coarse particles (PM10

and larger) at causing visibility impairment. Naturally occurring visual range in the Eastern United

States is estimated to be between 60 and 80 miles,

while natural visual range in the Western United

States is between 110 and 115 miles (these estimates

do not consider the effect of natural fire on visibility)

(Trijonis and others 1991). Currently, visual range in

the Eastern United States is about 15 to 30 miles and

about 60 to 90 miles in the Western United States. (40

CFR Part 51). The theoretical maximum visual range

about 240 miles.

Regional Haze

Regional haze is visibility impairment produced by

a multitude of sources and activities that emit fine

particles and their precursors and are located across a

broad geographic area. This contrasts with visibility

impairment that can be traced largely to a single, large

pollution source. Until recently, the only regulations

for visibility protection addressed impairment that is

reasonably attributable to a permanent, large emissions source or small group of large sources. In 1999,

EPA issued regional haze regulations to manage and

mitigate visibility impairment from the multitude of

diverse regional haze sources (40 CFR Part 51). The

regional haze regulations call for States to establish

Figure 2-2—Mandatory class 1 areas (Hardy and others 2001).
14 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

goals for improving visibility in Class I National Parks

and wildernesses, and to develop long-term strategies

for reducing emissions of air pollutants that cause

visibility impairment.

Regional Haze Planning Process—Because regional haze is a multi-State issue, regional haze regulations encourage States, land managers, and other

stakeholders to work together to develop control programs through regional planning organizations that

can coordinate development of strategies across a

multi-State region. In the Western United States, the

Western Regional Air Partnership (WRAP), sponsored

through the Western Governors’ Association and the

National Tribal Environmental Council, is coordinating regional planning and technical assessments. The

WRAP was the first of five regional planning organizations to be established and has been active in many

technical and policy developments. Other regional

planning organizations have begun assessments of

fire and air quality in their regions. In the Eastern

United States, four formal groups are addressing

planning issues: CENRAP (Central States Regional

Air Partnership), OTC (Ozone Transport Commission), VISTAS (Visibility Improvement State and Tribal

Association of the Southeast); and the Midwest Regional Planning Organization (fig. 2-3).

As inter-State smoke transport becomes a larger

issue, agencies are expanding coordination of their

burns. Multi-State, interagency partnerships are developing to help coordinate burning and mitigate cumulative impacts of smoke. For example, the Montana/Idaho airshed group includes private, State,

Tribal, and Federal partners in supporting an integrated smoke management program that includes

emissions monitoring and smoke forecasting (Levinson

2001).

Regional Haze and Fire Emissions—The adoption of regional haze regulations marks a turning

point in how fire emissions are treated under the

nation’s Federal and State air quality regulations,

Figure 2-3—Regional air quality planning groups (Hardy and others 2001).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 15

although the regulations leave several definitions

open to subsequent policy interpretation:

• The role of fire in forest ecosystems is formally

recognized for the first time.

• Emissions from “natural” sources are distinguished from “anthropogenic” sources and

treated differently under the rule.

• The rule is the first to require development of

emissions inventories for fire, including wildland fires.

• Emissions from fire are now subject to regional air quality planning processes as well

as requirements to achieve “reasonable

progress” in emissions reductions

The policy discussion to determine what types of fire

emissions are considered natural is still in progress,

but the WRAP has recommended a national policy

that would (1) define “natural background” as fire

emissions that would occur in the future without fire

management; that is, without reference to historic fire

occurrence or historic vegetation types; and (2) include

prescribed burning as natural sources of visibility

impacts when fire is used to maintain healthy and

sustainable ecosystems.

Current data from a national visibility-monitoring

network (Sisler and others 1996) do not show fire to be

the predominant long-term source of visibility impairment in any Class I area (40 CFR Part 51), although

emissions from fire are an important episodic contributor to visibility-impairing aerosols. Certainly the

contribution to visibility impairment from fires can be

significant over short periods, but fires in general

occur relatively infrequently and thus have a lesser

contribution to long-term averages. Specific goals for

visibility improvement focus efforts on improving air

quality on the most impaired days, so fires may prove

to be an important target for control efforts in some

areas

Fire Consortia for Advanced Modeling of Meteorology and Smoke (FCAMMS)—Multiagency

consortia are building in the Pacific Northwest, Rocky

Mountain region, and Northeastern and Southeastern United States as part of the U.S. Department of

Agriculture, Forest Service, Fire Consortia for Advanced Modeling of Meteorology and Smoke. The Pacific Northwest consortium is developing a real-time

smoke prediction and emission tracking system that

addresses needs of several smoke management plans

from collaborating States, Tribes, and local air agencies (Ferguson and others 2001). California and

Nevada are working together through the California

and Nevada Smoke and Air Committee (CANSAC)

with similar objectives of tracking and predicting

cumulative smoke impacts (Chris Fontana, personal

communication).

Each group or regional consortium must respond to

local, State, and Tribal smoke management programs.

In addition, each region of the country has its own

particular atmospheric processes that impact fire behavior and smoke dispersion in different ways. For

example, while in the Southeast, timing of frontal

passages and onshore flow regimes become critical, in

the Western United States, complex flow through

mountainous terrain is an important consideration in

managing smoke. These regionally specific demands

are forcing research to focus on subtle aspects of smoke

emissions and dispersion instead of traditional development of worst-case air pollution scenarios.

Reasonable Progress

Visibility rules require States to make “reasonable

progress” toward the Clean Air Act goal of “prevention

of any future, and the remedying of any existing,

impairment of visibility.” The regional haze regulations did not define visibility targets but instead gave

States flexibility in determining reasonable progress

goals for Class I areas. States are required to conduct

analyses to ensure that they consider the possibility of

setting an ambitious reasonable progress goal, one

that is aimed at reaching natural background conditions in 60 years. The rule requires States to establish

goals for each affected Class I area to (1) improve

visibility on the haziest 20 percent of days, and (2)

ensure no degradation occurs on the clearest 20 percent of days over the period of each implementation

plan.

States are to analyze and determine the rate of

progress needed for the implementation period extending to 2018 such that, if maintained, this rate

would attain natural visibility conditions by the year

2064. To calculate this rate of progress, each State

must compare baseline visibility conditions to estimate natural visibility conditions in Class I areas and

to determine the uniform rate of visibility improvement that would need to be maintained during each

implementation period to attain natural visibility conditions by 2064. Baseline visibility conditions will be

determined from data collected from a national network of visibility monitors representing all Class I

areas in the country for the years 2000 to 2004. Each

State must determine whether this rate and associated emissions reduction strategies are reasonable

based on several statutory factors. If the State finds

that this rate is not reasonable, it must provide a

demonstration supporting an alternative rate.

Hazardous Air Pollutants _________

Hazardous air pollutants (HAPs) are identified in

Title III of the Clean Air Act Amendments of 1990
16 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

(PL101-549) as 188 different pollutants “which present,

or may present, through inhalation or other routes of

exposure, a threat of adverse human health or environmental effects whether through ambient concentrations, bioaccumulation, deposition, or other routes.”

The list of HAPs identified in the Clean Air Act are

substances that are known or suspected to be carcinogenic, mutagenic, teratogenic, neurotoxic, or which

cause reproductive dysfunction.

EPA Interim Air Quality Policy on

Wildland and Prescribed Fires_____

In 1998, the EPA issued a national policy to address

how best to achieve national clean air goals while

improving the quality of wildland ecosystems through

the increased use of fire. The Interim Air Quality

Policy on Wildland and Prescribed Fires (U.S. Environmental Protection Agency 1998) was developed

through a partnership effort involving EPA, the U.S.

Departments of Agriculture, Defense, and the Interior, State foresters, State and Tribal air regulators,

and others. The group that developed the policy relied

on the assumption that properly managed prescribed

fires can improve the health of wildland ecosystems

and reduce the health and safety risks associated with

wildfire, while meeting clean air and public health

goals through careful planning and cooperation

among land managers, air quality regulators, and local

communities.

Natural Events Policy ____________

PM10 NAAQS exceedances caused by natural events

are not counted toward nonattainment designation if

a State can document that the exceedance was truly

caused by a natural event and prepares a natural

events action plan (NEAP) to address human health

concerns during future events (Nichols 1996). Natural

events are defined by this policy as wildfire, volcanic,

seismic, and high wind events.

A wildfire NEAP should include commitments by

the State and stakeholders to:

1. Establish public notification and education programs.

2. Minimize public exposure to high concentrations

of PM10 due to future natural events such as by:

a. Identifying the people most at risk.

b. Notifying the at-risk public that an event is

active or imminent.

c. Recommending actions to be taken by the

public to minimize their pollutant exposure.

d. Suggesting precautions to take if exposure

cannot be avoided.

3. Abate or minimize controllable sources of PM10

including the following:

a. Prohibition of other burning during pollution

episodes caused by wildfire.

b. Proactive efforts to minimize fuel loadings in

areas vulnerable to fire.

c. Planning for prevention of NAAQS exceedances

in fire management plans.

4. Identify, study, and implement practical mitigating measures as necessary.

5. Periodic reevaluation of the NEAP.

Collaboration Among

Stakeholders ___________________

Because smoke from fire can negatively affect public

health and welfare, air quality protection regulations

must be understood and followed by responsible fire

managers. Likewise, air quality regulators need an

understanding of how and when fire use decisions are

made and should become involved in fire and smoke

management planning processes, including the assessment of when and how alternatives to fire will be

used. Cooperation and collaboration between fire

managers and air quality regulators is of great importance. Table 2-2 contains recommendations for various types of cooperation by these two groups depending on the applicable air quality protection instrument.

Best Available Control

Measures ______________________

The application of best available control measures

(BACM) for prescribed fire is a required element of

State implementation plans for PM10 nonattainment

areas that are significantly impacted by prescribed

fire smoke (EPA 1992a). The application of BACM is

also a requirement of EPA’s Air Quality Policy on

Wildland and Prescribed Fires (EPA 1998) (see “Prior

Work” section in chapter 1). EPA’s BACM guidance

includes basic smoke management program elements

and emissions reduction techniques that can be used

by land managers to minimize air quality impacts

from fire. These program elements and emissions

reduction techniques are fully documented in the

Smoke Management Guide for Prescribed and Wildland Fire: 2001 Edition (Hardy and others 2001).

Briefly, the BACM guidance notes that there are

two basic approaches to minimizing the impact of

prescribed fire on air quality: reducing the amount of

pollutants emitted, or reducing the impact of the

pollutants emitted on sensitive locations or regional

haze through smoke dilution or transport (redistributing emissions). Although each method can be discussed
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 17

independently, fire practitioners often choose fire and

fuels manipulation techniques that complement or are

at least consistent with meteorological scheduling for

maximum smoke dispersion and favorable plume transport. The following emissions reduction and redistributing emissions techniques are a compilation of our

knowledge base, and depending on specific fire use

objectives, the project locations, time, and cost constraints may or may not be applicable.

Reducing Emissions

At least 24 methods within six major classifications

have been used to reduce emissions from prescribed

burning (Hardy and others 2001). These techniques

include methods designed to minimize emissions by

reducing the area burned; reducing the fuel load by

reducing the fuel production, or fuel consumption, or

both; scheduling burns before new fuels appear; and

increasing combustion efficiency. Each of these methods has specific practices associated with it.

Redistributing Emissions

These measures are commonly practiced in smoke

management programs and include burning when

dispersion is good, cooperating with other burners in

Table 2-2—Recommended cooperation between wildland fire managers and air quality regulators, depending on air quality

protection instrument (Hardy and others 2001).

Air quality protection instrument Wildland fire managers Air quality regulators

National ambient air quality standards (NAAQS) Awarea Lead b

Attainment status Aware Lead

State implementation plan (SIP) planning and development Involvedc Lead

Conformity Involved Lead

Smoke management programs Partnerd Lead

Visibility protection Involved Lead

Regional planning groups Partner Lead

Natural emissions Partner Lead

Natural events action plan Partner Lead

Land use planning Lead Involved

Project NEPA documents Lead Involved

Other fire planning efforts Lead Involved

a

Aware: Responsibility to have a complete working knowledge of the air quality protection instrument but likely little or no involvement in its

development or daily implementation. b

Lead: Responsibility to initiate, bring together participants, complete, and implement the particular air quality protection instrument. c

Involved: Responsibility to participate in certain components of development and implementation of the air quality protection instrument although

not at full partner status. d

Partner: Responsibility to fully participate with lead organization toward development and implementation of the air quality protection instrument

in a nearly equal relationship.

a single airshed to schedule burns, avoiding sensitive

areas, burning smaller units, and burning more

frequently.

Ozone and Fire _________________

Ozone is a criteria air pollutant, but there is little

monitoring or research data that directly link fire

emissions with ground-level ozone concentrations.

Regulating efforts to reduce ozone have therefore

focused on more obvious industrial and urban sources

of the pollutants that form ozone (NOX and VOCs).

Fires are known to emit VOCs and a minor amount of

NOX, but much is uncertain about the magnitude of

ozone formation in the plume, the degree of mixing

with urban sources of ozone precursors, and transport

of ozone to ground level. EPA plans to begin including

fire emissions in future regional ozonestrategy modeling. Field observations of ozone formation in smoke

plumes from fires date back nearly 25 years when

measurements from aircraft detected ozone at the

edge of forest fire smoke plumes aloft. A recent study

(Wotawa and Trainer 2000) did link high ground-level

ozone concentrations to forest fire plumes that had

been transported great distances. Chapter 6 explores

these issues more fully.
18 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Notes

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 19

Chapter 3: Overview of Air

Pollution from Fire

This chapter provides a brief overview of and an

appreciation for the national, regional, and local importance of smoke to ambient air quality. We discuss

the significance of fire emissions and air quality impacts on a national and regional scale. Chapter 7 of

this document adds additional depth to this discussion.

Magnitude of Fire

Contributions___________________

Air quality impacts associated with wildland fires

are distinguished from those resulting from prescribed

burning because emissions from these two sources

have in the past been treated differently under the

Clean Air Act and by State and local air quality

regulations. In addition, it is important to have a

historical perspective of these issues given the increased use of fire in the recent past.

A comparison by Leenhouts (1998) of estimated

levels of biomass burning suggests that 10 times more

area burned annually in the pre industrial era than in

the contemporary era. After accounting for land use

changes such as urbanization and agriculture,

Leenhouts concluded that about 50 percent of historical levels would burn today if historical fire regimes

were restored to all wildlands to maintain ecosystem

health (figs. 3-1 and 3-2). This suggests a four- to sixfold increase from the current magnitude of wildland

fire emissions.

This section discusses: (1) smoke from wildland

fires; (2) smoke from prescribed fires; (3) impacts on

national ambient air quality standards (NAAQS); (4)

and magnitude with respect to regional and subregional scale visibility degradation. The second section

discusses smoke management programs.

Smoke from Wildland Fires

Although wildland fires occur throughout the nation, the largest fires and greatest number of fires

occur in Alaska, the Southeastern States, and the

West. Figure 3-3 shows the location of major fires

during the 2000 fire season when 90,674 fires burned

7,259,159 acres (2,938,931 ha) at a fire suppression

cost of $1.6 billion. The 10-year average acreage burned

between 1990 and 1999 was 3.78 million acres (1.53

million ha), testifying to the severity of the 2000

wildfire season. Figure 3-4 shows those States that

had more than 100,000 acres (40,486 ha) burned per

year, on average, over the 1987 through 1997 period,

illustrating that Alaska wildfires burn far more

acres than fires in any other State. Area burned in

California, the States in the Intermountain West,

Florida, and the Southwest follow (Peterson 2000).
20 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Figure 3-2—Estimated annual preindustrial, expected contemporary, and contemporary biomass consumed (Tg x102

) for

the conterminous United States (from Leenhouts 1998).

Wildfires occur throughout the year. The 2000 wildfire season began with a Florida fire on January 1,

continued with two 40,000-acre fires in New Mexico,

an early May, 47,000-acre fire near Los Alamos and

peaked on August 29, 2000, when fires that eventually

burned 1,642,579 acres were burning in 16 States

(NIFC 2001a). Generally, the occurrence of wildfires

moves northward from the Southeastern and Southwestern States as summer approaches, fuels dry and

fire danger increases.

Figure 3-1—Estimated annual preindustrial, expected contemporary, and contemporary area (Mha) for the conterminous

United States (from Leenhouts 1998).

Wildfires, both in number and total acreage burned,

vary widely from year to year and from region to

region. Figures 3-5 and 3-6 show no consistent relation

between the number of fires and acres burned. It is

known, however, that smoke from these fires impacts

air quality on both an episodic and long-term average

basis over wide regions.

Wildfires occur as episodic events. For example, in

1999, smoke from fires reduced visibility to less than

100 feet (30 m) in Florida, prompting officials to advise

people with respiratory problems to stay indoors (New

York Daily News 1999). In the West, fires in six States

(California, Nevada, Oregon, Montana, Washington,

and Idaho) put thick smoke in many communities. In

Reno and cities in California’s Central Valley, smoke

from nearby wildfires prompted authorities to warn

residents with asthma to avoid unnecessary activity

(USA Today 1999). Wildfire smoke is also transported

across international boundaries. Fires in Canada were

found to cause high concentrations of carbon monoxide

and ozoneover a period of 2 weeks in the Southeastern

United States and across the Eastern seaboard during

the summer of 1995 (Wotawa and Trainer 2000).

Smoke impacts during these episodic events can

threaten public health, cause smoke damage to buildings and materials, and disrupt community activities.

Although particulate concentrations in ambient air

rarely reach health-threatening levels within major

cities, several communities in the United States have

experienced particulate matter concentrations from

wildfire smoke that exceeded the Environmental Protection Agency (EPA) significant harm emergency

action level of 600 μg/m3 defined as an “imminent and

substantial endangerment of public health” (EPA

1992b).

For example, the Yellowstone National Park wildfires

of 1988 impacted communities in three States. Concentrations of suspended particulate matter — both total

suspended particulate (TSP) and PM10 — measured in

communities near the fires exceeded NAAQS, triggering

public health alerts and advisories (Core 1996). An

estimated 200,000 people were exposed to high concentrations of smoke. In 1987, the Klamath fires of northern

California burned for more than 60 days, resulting in

widespread smoke intrusions into numerous communities in northern California and southern Oregon. More

recently, wildfire impacts during the 2000 season were

also severe in several communities. Twenty-four average PM10 concentration measured in Salmon, ID, reached

225 μg/m3 on August 15, 2002, and 281 μg/m3 on August

18, 2000, during wildfire smoke intrusions (Idaho Department of Environmental Quality n.d.).

Wildfire smoke can also be the dominant cause of

visibility reduction during episodic events in the

Rocky Mountain States, on the Pacific Coast, and in

the Southeast (National Research Council [NRC]
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 21

Figure 3-3—Location of major wildfires in 2000 available at http://www.nifc.gov/fireinfo/2000/Top10fires.html.

Figure 3-4—States with more than 100,000 acres per year burned by wildfires.

Wildfire Acreage for States Exceeding 100,000 Acres

Average Acreage 1987–1997

Oklahoma

Arizona

Utah

Nevada

Montana

Oregon

Kansas

New Mexico

Florida

Wyoming

Idaho

California

Alaska

State

Acres

0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 800,000 900,000
22 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Figure 3-5—Number of wildfires per year 1990 through 1999 (National Interagency Fire Center 2002).

Figure 3-6—Number of acres burned by wildfires per year 1990 through 1999.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 23

1993). Figures 3-7 and 3-8 are examples of the dense

plumes of smoke that can be transported over hundreds of kilometers across State and international

boundaries, degrading air quality, scenic values, and

highway safety. Between 1979 and 1988, 28 fatalities and more than 60 serious injuries were attributed to smoke that drifted across roadways in the

Southern United States (Mobley 1989).

Figure 3-7—Big Bar Fire, Shasta-Trinity National Forest, California, August 1999

(National Interagency Fire Center 2000).

Figure 3-8—Wildfire smoke transported across State lines, August 14,

2000 (NASA).
24 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Smoke from Prescribed Fires

On a national annual basis, PM10 emissions from

prescribed burns in 1989 were estimated to be over

600,000 tons, half of which (380,000 tons) occurred in

the Southeastern States. Of the remaining 42 States,

seven (Arizona, California, Idaho, Montana, Oregon,

Texas, and Washington) were estimated to have annual emissions over 10,000 tons of PM10 from prescribed forest and rangeland burning (EPA 1992a;

Peterson and Ward 1990). More recent estimates of

prescribed fire PM2.5 emissions in the West (EPA

regions 8, 9 and 10) totaled 193,293 tons (Dickson and

others 1994). These national, annual estimates are

less significant in terms of air quality impact than

those prepared at the State level. For example, the

211,000 tons of prescribed fire PM10 emissions in

Georgia in 1989 is about 30 percent of the total estimated particulate inventory for all sources (EPA

1992a). On a seasonal basis, emissions from prescribed burning are likely to be an even more significant percentage of total emissions in some States.

Acreage treated by prescribed burning on Federal

lands increased from 918,300 acres in 1995 to 2,240,105

acres in 1999, demonstrating renewed interest in the

use of fire as an important tool in the management of

wildlands (NIFC 2001b).

Impacts on National Ambient Air Quality

Standards

Characterization of the true extent of effects of

prescribed and wildland fires on ambient air quality is

incomplete due to the deficiency of air quality monitoring sites in rural areas. Also, particulate standards are

based on 24-hour and annual averages, whereas smoke

plumes may significantly degrade air quality in a

community for just a few hours before moving or

dispersing. These short-term, acute impacts likely

cause discomfort at the least, and possibly even affect

health, but may not result in a violation of the NAAQS.

Numerous exceedances of 24-hour PM10 and PM2.5

standards have been attributed to wildfires but, as

mentioned previously, violations of NAAQS caused by

wildfire do not result in nonattainment if a State can

document that the cause of the violation was truly

wildfire and then prepares a natural events action

plan for future events.

At present, prescribed fires are not considered to be

a significant cause of nonattainment, but with increased burning to reduce fuels, this situation may

change as land managers move forward with implementing a several-fold increase in the use of fire to

sustain ecosystems (USDI and USDA 1995; USDA

1997). In general, little information is available on a

national level to identify the contribution of prescribed

burning to PM10 or PM2.5 within nonattainment

areas (EPA 1992a). It appears, however, that there is

no clear relation between total acres burned (or particulate emissions) and the nonattainment status of

nearby airsheds, possibly because of successful smoke

management programs.

In areas where air quality standards are being or

may be violated, however, land managers are being

directed to reduce air quality impacts through smoke

management programs. This is because any source

that contributes even a few micrograms per cubic

meter of particulate matter toward violation of the

NAAQS may be required to reduce emissions to assure

that air quality standards are attained.

Significance of Visibility Degradation

As noted above, wildland fires can significantly

degrade visibility during episodic events. With the

new emphasis on the reduction of regional haze in the

Class I National Parks and wilderness areas of the

nation, smoke from fire is of special concern, especially

in the West. In their report to the EPA, the Grand

Canyon Visibility Transport Commission (GCVTC)

noted that emissions from fire, both wildland fire and

prescribed fire, are likely to have the single greatest

impact on visibility at Class I areas through 2040.

During periods of intense fire activity, smoke from

wildland fires is likely to make the worst 20 percent of

days at the Grand Canyon even worse rather than

impair visibility on clear days (GCVTC 1996b). The

Commission recommended several actions to reduce

impacts on regional haze including enhanced smoke

management programs and establishment of annual

emissions goals for all fire programs.

Greenhouse Gas Emissions from Fires

Globally, fires are a significant contributor of carbon

dioxide and other greenhouse gases in the atmosphere.

Fires account for approximately one-fifth of the total

global emissions of carbon dioxide (Levine and Cofer

2000; Schimel 1995). Andreae and Merlet (2001) calculate that 5,130 Tg per year of biomass is consumed

in fires, emitting 8,200 Tg per year of carbon dioxide,

413 Tg per year of carbon monoxide, and 19.4 Tg per

year of methane. The accuracy of these global estimates is thought to be within plus or minus 50 percent,

with the bulk of the error resulting from inaccuracies

in the estimates of the area burned and the mass of

fuel consumed.

Fires in temperate ecosystems are minor contributors compared to the world’s savannas, boreal forests,

and tropical forests. More than 60 percent of the totals

listed in the previous paragraph are released from

savannas and grasslands, and another 25 percent

from tropical forests. Burning in tropical Africa is

dominated by savanna fires; in tropical Asia, by forest
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 25

fires; and in tropical South America, about equally

represented by savannas and tropical forests (Hao and

Liu 1994). Lavoué and others (2000) detail contributions from temperate and boreal fires, demonstrating

that about 90 percent of the global boreal fire area is

in Russia and Canada. Alaska accounts for only about

4.5 percent of the global boreal forest, but it accounts

for at least 10 percent of the emissions from that

source, because of the heavier fuel loads in Alaska.

Alaska accounts for an average of 41 percent of total

U.S. fire emissions, with a huge year-to-year variability. In 1990, 89 percent of U.S. fire emissions were

from Alaska fires.

Smoke Management

Programs ______________________

Smoke management programs establish a basic

framework of procedures and requirements when

managers are considering resource benefits. These

programs are typically developed by States and Tribes

with cooperation and participation by wildland owners and managers. The purposes of smoke management programs are to mitigate the nuisance (such as

impacts on air quality below the level of ambient

standards) and public safety hazards (such as visibility on roads and airports) posed by smoke intrusions

into populated areas; to prevent significant deterioration of air quality and NAAQS violations; and to

address visibility impacts in Class I areas.

The Interim Air Quality Policy on Wildland and

Prescribed Fires (EPA 1998) provides clear guidelines

for establishing the need for and content of smoke management programs and assigns accountability to State

and Tribal air quality managers for developing and

adopting regulations for a program. Measured PM10

NAAQS exceedances attributable to fires, including

some prescribed fires and wildland fires managed for

resource benefits, can be excluded from air quality data

sets used to determine attainment status for a State.

Special consideration will be given if the State or Tribal

air quality manager certifies in a letter to the administrator of EPA that at least a basic smoke management

program has been adopted and implemented.

States with smoke management programs that have

authorized a central agency or office to make burn/noburn decisions include Arizona, Colorado, Oregon,

Idaho/Montana, Washington, California, Nevada, New

Mexico, Florida, South Carolina, Utah, North Carolina, and Wyoming (Battye and others 1999). In many

other States, the decision to burn rests in the hands of

the persons conducting the burn, local fire departments, or local authorities. These States include Alaska,

Alabama, Arkansas, Georgia, Louisiana, Mississippi,

Tennessee, Texas, and Virginia. In yet other States

(New York, Illinois, Massachusetts, and others), burn

permits are required and may be subject to State air

agency oversight if burning is conducted near

nonattainment areas or areas sensitive to smoke (Core

1998; Hardy and others 2001). In addition, many

private landowners, nonprofit conservation organizations and government agencies voluntarily practice

responsible smoke management to maintain goodwill

in their communities.

Smoke management programs have been established and are operated on an on-going basis because

of local, regional, and national concerns about the

impact of prescribed burning on air quality. The number, complexity, and cost of operating these programs

underscore the potential significance of prescribed

fire’s impact on air quality on a national scale.

Smoke management programs across the nation

have changed significantly since the mid-1980s. In the

Pacific Northwest, there have been reductions in prescribed fire smoke management programs because of

the decline in large-scale clearcut burning of forest

harvesting residues. Current smoke management programs across the West have to place a much greater

focus than in the past on understory burning to restore

declining forest health, on burns to reduce fire hazards, or on burns to meet wildlife habitat objectives.

All across the nation, an increasing number of people

living within the wildland-urban interface have placed

new emphasis on the need to minimize smoke impacts

on residents living near fires. Increasing air quality

regulatory pressures, fire manager liability issues,

and the increased likelihood of fire escapement in

overstocked forestlands have all placed ever-greater

demands on fire practitioners.

As these demands have increased, so have the

number and complexity of smoke management programs nationwide (Hardy and others 2001). Although

the complexity of these programs varies widely from

State to State, the key to a successful program always

lies in its ability to balance the use of prescribed fire

with air quality, environmental, legal, and social

requirements. Increasingly, this has meant adoption

of formalized burn authorization procedures issued

by program managers who are responsible for overseeing burning on both public and private lands on a

daily basis. Coordinated burn operations are based

on meteorological forecasts, the location of smokesensitive receptors, fuel conditions, and a myriad of

other considerations. Increasingly, public notification of planned burning activity and monitoring of

smoke transport, as well as fire practitioner training

and program enforcement, are becoming more common (Battye and others 1999).

As inter-State smoke transport becomes a larger

issue, agencies are expanding coordination. For example, land management agencies in California’s
26 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

San Joaquin Valley are using a new centralized,

electronic database, Prescribed Fire Incident Reporting System (PFIRS), to schedule fires and to share

information on expected emissions and smoke transport with California and Nevada air and land management agencies (Little n.d.). This trend is likely to

continue as States begin to work on regional haze

control programs.

The Western Regional Air Partnership (WRAP) Fire

Emissions Joint Forum (FEJF) has issued a draft

policy to set the criteria for enhanced smoke management plans for visibility protection in the West (Fire

Emissions Joint Forum 2002). The policy document

concludes that the regional haze rule can be satisfied

only by the States and Tribes establishing an emission

tracking system for all prescribed fires and wildland

fires; by managing smoke from all fires; and by implementing smoke management systems that include

nine elements:

1. Actions to minimize emissions from fire

2. Evaluation of smoke dispersion

3. Alternatives to fire

4. Public notification of burning

5. Air quality monitoring

6. Surveillance and enforcement

7. Program evaluation

8. Burn authorization

9. Regional coordination

The enhanced smoke management plan (ESMP)

policy would enable Western States and Tribes to

minimize increases in emissions and show reasonable

progress toward the natural visibility goal. The Fire

Emissions Joint Forum is developing additional policy

and technical tools that will support ESMP policy and

its implementation, such as recommendations for creation of an annual emissions goal, availability and

feasibility of alternatives to burning, recommendations for managing fire emissions sources, guidance

for feasibility determinations, and a method for tracking fire emissions.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 27

All fires emit air pollutants in addition to nonpolluting combustion products; but fires vary widely in what

pollutants are emitted in what proportion. Characterizing and managing air pollution from fires first requires knowledge of the amount and timing of what

pollutants are emitted. Fires are a complex combustion source that involve several stages of combustion,

several categories of fuels, and fire behavior that

changes over time and with fuel and weather conditions; so the amount, rate, and nature of pollutants

also vary widely. Characterizing emissions from fires

requires explicit knowledge of fuelbed character and

condition, combustion environment, and fire behavior.

This chapter reviews the state of knowledge and

predictive models necessary to characterize air pollutant emissions from prescribed and wildland fires.

All components of smoke from fires, with the exception of carbon dioxide and water, are generated from

the inefficient combustion of biomass fuels. The amount

of smoke produced is derived by determining the fuel

consumed (tons per acre) in each combustion stage and

knowing the size of the area burned, fuel characteristics, fire behavior, and combustion conditions (fuel

moisture, weather parameters, and so forth). The fuel

Chapter 4:

Characterization of

Emissions from Fires

consumption is then multiplied by an emissions factor

for each pollutant, which is an expression of the

efficiency of combustion. An emission factor is the

ratio of the mass of pollutant per unit mass of fuel

consumed, and is a statistical average of measurements made in the plumes of fires containing differing

fuel types and combustion stages. Errors and uncertainties arise in the estimates made during each step

in the process of estimating emissions.

Area Burned____________________

At first glance, amount of area burned seems relatively easy to calculate. However, individual estimates of fire size tend to be systematically exaggerated, and fires are frequently double-counted in

inventories. For example, geographic features, nonuniform fuelbeds, or a change in the weather will often

cause a fire to create a mosaic of burned, partially

burned, and unburned areas, although the entire

landscape within the fire perimeter is often reported

as burned. In addition, large-scale (such as continental) inventories of area burned are often derived from

remote sensing data that have resolutions from 250 m

to 1 km (SAI 2002), limiting their precision. Remote
28 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

sensing accuracy is currently inadequate in landscapes that change slope and fuel characteristics over

a few tens of meters.

Preburn Fuel Characteristics ______

Large variations in fuel characteristics can contribute up to 80 percent of the error associated with

predicting emissions (Peterson 1987; Peterson and

Sandberg 1988). Fuel characteristics can vary widely

across the landscape (figs. 4-1 and 4-2). For instance,

fuel loads can range from less than 3 tons per acre for

perennial grasses with no rotten woody material or

duff, 6 tons per acre in a sagebrush shrubland, 60 tons

per acre in a ponderosa pine and Douglas-fir forest

with rotten woody material, stumps, snags, and deep

duff, to 160 tons per acre in a black spruce forest with

deep moss and duff layer. The greatest errors occur

when the fuel load is inferred from vegetation type as

is usual when deriving biomass emissions from remotely sensed data (Crutzen and Andrae 1990; Levine

1994). Preburn fuel characteristics, such as relative

abundance for particular fuelbed components (grasses,

shrubs, woody fuels, litter, duff, and live vegetation)

and the condition of the fuel (live, dead, sound, rotten)

are needed to calculate fuel consumption, and the

resulting smoke.

The ongoing development of several techniques,

including the natural fuels photo series (Ottmar and

Vihnanek 2000a) and the fuel characteristic classification (FCC) system (Sandberg and others 2001), will

provide managers new tools to better estimate fuel

loadings and reduce the uncertainty that currently

exists when assigning fuel characteristics across a

landscape. The photo series is a sequence of single and

stereo photographs with accompanying fuel characteristics. The FCC is a national system designed for

classifying wildland fuelbeds according to a set of

Figure 4-1—Fuelbed types and fuel loads (a) grassland (3 tons per acre), (b) sagebrush (6 tons per acre), (c) ponderosa

pine with mortality in mixed fir (60 tons per acre), and (d) black spruce with deep duff and moss (160 tons per acre).

(Photos by Roger Ottmar)

d

a

c

b
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 29

inherent physical properties, thereby providing the

best possible fuels estimates and probable fire parameters based on available site-specific and remotely

sensed information.

Fire Behavior ___________________

Fire behavior is the manner in which fire reacts to

the fuels available for burning (DeBano and others

1998) and is dependent upon the type, condition, and

arrangement of fuels, local weather conditions, topography, and in the case of prescribed fire, ignition

pattern and rate (fig. 4-3). Important aspects of fire

behavior include:

• Fire intensity (rate of energy release per unit

area or unit length of fire perimeter, generally

during the flaming combustion period).

• Rate of spread (rate of advancement of flaming

front, length per unit time), crowning potential (involvement of tree and shrub foliage and

spread within the canopy), smoldering potential (smoldering combustion of fuels that have

been preheated or dried during the flaming

stage).

• Residual smoldering potential (propagation of

a smoldering combustion front within porous

fuels such as rotten logs or duff, independent

of preheating or drying).

• Residence time in the flaming, smoldering,

and residual stages of combustion.

These aspects influence combustion efficiency of consuming biomass, as well as the resulting pollutant

chemistry and emission factor (fig. 4-4).

The Emissions Production Model (EPM) (Sandberg

2000; Sandberg and Peterson 1984) and FARSITE

(Finney 1998) take into account fire behavior and

ignition pattern to estimate emission production rates.

Fire behavior during the flaming stage of combustion

in surface woody fuels and some shrub vegetation is

effectively predicted within models such as BEHAVE

(Andrews and Bevins 1999) and its spatial application, FARSITE (Finney 1998). However, EPM and

other applications do not consider fire intensity or

other fire behavior attributes when estimating emissions from flames, and that may result in a reasonable

approximation for criteria pollutants but also be a

limitation to the estimate of hazardous air pollutants

or trace gases. BURNUP (Albini and Reinhardt 1997),

FARSITE (Finney 1998), and EPM v2.0 (Sandberg

2002) attempt to model the extent and duration of

flaming and smoldering combustion in downed woody

fuels and duff. Current capability to model residual

combustion, combustion in rotten logs and duff, and

fire behavior in the foliage canopies of trees and some

shrubs remains inadequate to predict emission rates

with any reasonable degree of accuracy.

The Los Alamos and Lawrence Livermore national

laboratories offer an approach to predicting fire behavior, plume trajectory, and dispersion, by combining a fire physics model, FIRETEC, with a dynamic

atmosphere model, HIGRAD, to produce a highly

detailed numerical simulation of fire spread and atmospheric turbulence (Bradley and others 2000). The

approach builds on prior experience in predicting the

dispersion of hazardous air pollutants from fires such

as burning oil fields or “nuclear winter” scenarios.

This modeling approach is limited to the propagating

front but is unique in its coupling of atmospheric and

fire physics.

Figure 4-2—Various fuelbeds across a single landscape.

(Photo by Roger Ottmar)

Figure 4-3—Fire behavior in the leaf layer of a longleaf pine

forest. (Photo by Roger Ottmar)
30 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Figure 4-4—Fuel consumption in (a) large rotten log during

a fall prescribed burn, (b) pile burning during a prescribed

burn, (c) litter and duff during a prescribed burn, (d) grass

during a wildfire, and (e) sagebrush during a prescribed fire.

(Photos by Roger Ottmar)

Combustion Stages _____________

At least three important stages of combustion exist

when fuel particles are consumed (Mobley 1976; NWCG

1985): flaming, smoldering, and residual (also known

as “glowing,” “residual smoldering,” or “residual combustion”) (fig. 4-5). The efficiency of combustion is

distinct for each stage, resulting in a different set of

chemical compounds and thermal energy being released at different rates into the atmosphere. In the

flaming phase, combustion efficiency is relatively high

and usually tends to emit the least amount of pollutant

emissions compared with the mass of fuel consumed.

The predominant products of flaming combustion

are CO2 and water vapor. During the smoldering

phase, combustion efficiency is lower, resulting in

more particulate emissions generated than during the

flaming stage.

Smoldering combustion is more prevalent in certain

fuel types such as duff, organic soils, and rotten logs,

and often less prevalent in fuels with high surface to

volume ratios such as grasses, shrubs, and small

diameter woody fuels (Sandberg and Dost 1990).

a b

c d

e
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 31

Figure 4-5—Flaming, smoldering, and residual combustion

stages during a fire. (Photo by Roger Ottmar)

The residual stage differs from the smoldering stage

in that the smoldering stage is a secondary process

that occurs in fuels preheated or dried by flaming

combustion, while residual is an independent process

of propagation in a fuelbed unaffected by the flaming

stage. This phase is characterized by little smoke and

is composed mostly of CO2 and carbon monoxide. All

combustion stages occur sequentially at a point, but

simultaneously on a landscape.

Fuel Consumption_______________

Fuel consumption is the amount of biomass consumed during a fire and is another critical component

required to estimate emissions production from fire.

Biomass consumption varies widely among individual

fires depending on the fuelbed type, arrangement, and

condition, weather parameters, and the way the fire is

applied in the case of prescribed fire. As with fuel

characteristics, extreme variations can be associated

with fuel consumption resulting in an error contribution of 30 percent or more when emissions are estimated (fig. 4-6) (Peterson 1987; Peterson and Sandberg

1988).

Biomass consumption of woody fuels, piled slash,

and duff in forested areas has become better understood in recent years (Albini and Reinhardt 1997;

Brown and others 1991; Ottmar and others 1993;

Ottmar and others [N.d.]); Reinhardt and others 1997;

Sandberg 1980; Sandberg and Dost 1990). Consumption of forested crowns and shrublands are the least

understood components of biomass consumption, and

research is currently under way (Ottmar and Sandberg

2000) to develop or modify existing consumption equations for these fuel components. Equations for predicting biomass consumption in the flaming and smoldering combustion stages are widely available in two

major software packages, Consume 2.1 (Ottmar and

others [N.d.]) and the First Order Fire Effects Model

(FOFEM 5.0) (Reinhardt and Keane 2000).

Figure 4-6—The largest errors are associated with fuel loading and fuel consumption

estimates when determining emission production and impacts from wildland fire (Peterson

and Sandberg 1988).
32 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Emission Factors _______________

Emissions from fires or from points over fires have

been observed extensively by researchers since about

1970. The result is a complete set of emission factors

(pounds of pollutant per ton of fuel consumed) for

criteria pollutants and many hazardous air pollutants

for most important fuel types. These are available in

several publications (for example, Battye and Battye

2002, EPA 1972, Hardy and others 2001, Ward and

others 1989) and are not reproduced here.

Less complete compilations of emission factors are

for particulate matter components such as size class

distribution, elemental and organic carbon fractions,

and particulate hazardous air pollutants; and for

methane, ammonia, aldehydes, compounds of nitrogen, volatile organic hydrocarbons, and volatile hazardous air pollutants (for example, Battye and Battye

2002, Goode and others 1999, Goode and others 2000,

Lobert and others 1991, McKenzie and others 1994,

and Yokelson and others 1996).

Source Strength ________________

Source strength is the rate of air pollutant emissions

in mass per unit of time, or in mass per unit of time per

unit of area. Source strength is the product of the rate

of biomass consumption (that is, fuel consumption)

and an emission factor for the pollutant(s) of interest

and is representative of the physical and chemical fuel

characteristics (fig. 4-7). Source strength or emission

rate is required as an input to dispersion models

(Breyfogle and Ferguson 1996), or to break down

emission inventories into time periods shorter than

the duration of a fire event. Source strength is also

required in photochemical models such as the community multiscale air quality model (CMAQ) (Byun and

Ching 1999) to account for timing of chemical reactions with diurnal patterns and interaction with other

sources.

Total emissions from a fire or class of fires are the

source strength integrated over the time of burning.

Total emissions from a single class of fires (that is, a

set of fires similar enough to be characterized by a

single emission factor) can be estimated by multiplying that emission factor by the level of activity, which

is the total biomass consumed by the class of fires. An

emission inventory is the aggregate of total emissions

from all fires or classes of fire in a given period for a

specific geographic area.

Managing the source strength (or level of activity) of

fires is the most direct way to control air pollution from

wildland and prescribed fires. Prediction of source

strength is sometimes used to manage the rate of

emissions from fires, and it also is needed as an input

to dispersion models. Standards or regulations are

commonly set to limit the total emissions of pollutants,

emission of specific hazardous air pollutants, or the

level of activity, so that estimates of biomass consumption can be essential for environmental assessment,

permitting of prescribed fires, or measuring compliance. Emission inventories are a critical part of impact

analyses and strategy development so the level of

activity must be estimated whenever there is a regulatory application.

The Emissions Production Model (Sandberg 2000;

Sandberg and Peterson 1984) is currently the most

widely used model for predicting source strength for

prescribed fires. EPM v.1 predicts flaming and residual emissions rates for each criteria pollutant

based on a simple formula that assumes a constant

rate of ignition of a prescribed fire in uniform fuels.

The software package pulls fuel consumption predictions from Consume 2.1 or FOFEM 5.0 and uses

ignition pattern, ignition periods, and burn area

components to calculate source strength for the flaming and residual combustion phases. EPM v.1 does

not consider smoldering emissions (for example, longduration, self-propagating glowing combustion),

multiple fires or multiple burn periods, wildland fire

or piled burning emissions, or diurnal and spatial

changes in the fire environment. EPM v.2, now under

development (Sandberg 2000), corrects all of these

shortcomings in a dynamic simulation model. EPM v.2

will satisfy the requirement to provide hourly estimates of emission rates for most fires and fuelbeds

needed for input into Models-3/CMAQ (see the “Grid

Models” section in chapter 5) and into currently

envisioned smoke management screening systems.

Figure 4-7—A high-intensity Alaska wildfire with heavy fuel

loads, causes a high rate of emissions. (Photo by Roger

Ottmar)
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 33

FARSITE (Finney 2000) has been modified to predict emissions source strength as well as fire behavior

in a detailed spatial simulation. FARSITE incorporates BURNUP (Albini and Reinhardt 1997), which

estimates consumption and rates of individual fuel

elements.

Accurate characterization of emissions from fires is

critical to predicting the impact emissions will have

upon communities and across broader landscapes and

airsheds. Managers will increasingly be required to

provide this type of information prior to prescribed

burns, as well as during the course of wildland fires,

and the information provided here summarizes the

strengths and weaknesses of the various means of

prediction.
34 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Notes

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 35

Chapter 5: Transport,

Dispersion, and Modeling of

Fire Emissions

To anticipate the impacts of smoke, the timing and

location of smoke concentrations become important.

Data on the site-specific surface concentrations of

respirable particles and gases often are needed for

estimating impacts on public health and welfare, requiring atmospheric dispersion and transport models

that can approximate the atmospheric physics and

chemical reactions that occur during transport near

the ground. Data on the cumulative concentrations of

elements that scatter and absorb light also are needed

to estimate impacts on visibility and haze, requiring

models that can approximate aqueous reactions as

well as physical and chemical reactions at all levels of

the atmosphere.

Although progress is being made, none of the currently available models fully meet the needs of fire

planners and air resource managers. Much of the

deficiency in current modeling approaches is caused

by inherent uncertainties associated with turbulent

motions between the fire, smoke, and the atmosphere

that are compounded by the highly variable distribution of fuel elements, composition, and condition.

Another source of deficiency is that most available

models were originally designed for well-behaved sources

such as industrial stacks or automobile emissions,

while emissions from fire can be extremely variable in

both time and space. Also, outputs from currently

available models do not always match the temporal or

spatial scale needed for land management application.

To help readers understand the strengths and weaknesses of available models, we describe basic elements

of the trajectory and dispersion of smoke. This chapter

concludes with a summary of currently available models and a brief guide to applications.

Basic Elements of Trajectory and

Dispersion _____________________

Ambient air quality can be measured at a point or as

distribution of air quality over any space and time of

interest. Ambient air quality is affected by the pollutants emitted to the atmosphere from fires, the background air quality that has already been degraded by

other sources, the transport of the polluted parcels of

the atmosphere, dispersion due to atmospheric movement and turbulence, secondary reactions, and removal processes. Plume rise is an important component

of transport, because it determines where in the vertical structure of the atmosphere dispersion will begin.
36 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Overall, dispersion has proven extremely difficult

to model accurately, especially in complex terrain.

For example, detailed, gridded, three-dimensional

meteorological data are required to model transport

and dispersion, but expert judgment is often required to supplement or substitute for such modeled

predictions.

Despite the difficulties of modeling, since about

1990 modeling systems used to assess the air quality

impact of fires have grown increasingly important to

both the fire planning and air quality communities.

There is a broad range of acceptable tools from relatively simple methods used by local fire managers for

estimating likely impacts on air quality standards (for

example, SASEM: Riebau and others 1988; and

VSMOKE: Lavdas 1996), to complex terrain and regional-scale models that incorporate atmospheric

chemistry to assess impacts on regional haze (for

example, Calpuff: Scire and others 2000a, and Models3: Byun and Ching 1999).

The tremendous growth in model application places

increasingly greater demands on the user, requiring

access to detailed fuel characteristics, fuel consumption, ignition pattern, fire behavior, and meteorological inputs. Also needed is the ability to interpret the

complex smoke dispersion model outputs.

In this section we describe such processes of heat

release, plume rise and buoyancy, advection and diffusion, scavenging, and chemical transformations.

Heat Release

The consumption of biomass produces thermal energy, and this energy creates buoyancy to lift smoke

particles and other pollutants above the fire. Heat

release rate is the amount of thermal energy generated per unit of time. Total heat release from a fire or

class of fires is a function of the heat content of the

biomass, fuel consumed, ignition method and pattern,

and area burned.

The early work of Anderson (1969) and Rothermel

(1972) created fundamental equations for combustion

energy in a variety of fuelbeds. Sandberg and Peterson

(1984) adapted the combustion equations to model the

temporal change in energy during flaming and smoldering combustion (Emission Production Model,

EPMv.1.02). Currently, EPM provides heat release

rates for most biomass smoke dispersion models

(Harms and others 1997; Harrison 1995; Lavdas 1996;

Sestak and Riebau 1988; Scire and others 2000a) and

has been used to estimate the change in global biomass

emissions patterns due to changes in land use

(Ferguson and others 2000). The model, however,

requires a constant rate of ignition with constant slope

and wind. Such homogeneous conditions may be approximated during prescribed fires that are ignited

with a deliberate pattern of drip torches or airborne

incendiaries, or during portions of wildfires that experience relatively constant spread rates, both over

fuelbed strata that retain a relatively consistent spatial and compositional pattern. To use EPM effectively

for modeling source strength, the fire area and ignition

duration are broken into space and time segments that

meet the steady-state criteria.

Albini and others (1995), Albini and Reinhardt (1995),

and Albini and Reinhardt (1997) do not explicitly

derive temporal changes in combustion energy in their

model, BurnUp, but they do assign source heat in

steps of flaming and smoldering that are estimated

from total fuel consumption. They have linked their

model with the fire spread model, FARSITE (Finney

1998), which allows ignition rates and subsequent

heat-release rates to vary over the landscape. The

coupled system is computationally expensive and not

yet associated with a plume rise component but may

offer a reasonable approximation of the temporal and

spatial varying emission rates of fires.

Plume Rise and Buoyancy

Heat, particle, and gas emissions from fires vary in

time and space, causing unique patterns of convection

and resulting plume rise. This plume rise is a function

of free convection in the atmosphere, which is caused

by density differences within the fluid. As a fire heats

and expands air near the ground, large density differences between the heated volume and the surrounding

air mass are created, causing the heated parcel to rise.

The potential height of the resulting plume depends

on the heat energy of the source and rise velocity,

which is affected by the exchange and conservation of

mass, radiant heat loss, the buoyancy force, and turbulent mixing with the ambient air.

Hot, flaming fires can develop central convective

columns with counter-rotating vortices that involve

massive entrainment of the surrounding air mass

(Clark and others 1996; Haines and Smith 1987;

Haines and Updike 1971). This stage of fire can produce fast-rising plumes and turbulent downdrafts,

carrying sparks that ignite new fires. Cumulonimbus

clouds often develop with accompanying lightning and

rain. Dynamic plume rise brings gas and particles

high into the atmosphere where strong winds can

disperse the smoke hundreds to thousands of kilometers. As high intensity fires cool, however, the central

column often collapses, creating numerous small convective cells that are less dynamic but equally active in

carrying smoke into the atmosphere. Smoldering fires

often create plumes that are neutrally buoyant, limiting widespread dispersion but allowing surface winds

to dominate smoke trajectories. This can lead to accumulations of smoke in valleys and basins at night.

Because plume rise can eventually result in widespread dispersion, plume rise calculations are essential
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 37

for determining the height above ground from which

plume dispersion is initiated. Uncertainties in such

calculations can result in inaccurate predictions of

plume transport and downwind smoke impacts. Given

the pressing need to predict the impact of plumes from

fires, the need for improved plume rise calculations is

apparent.

The basic mechanisms and algorithms used to describe plume rise and buoyancy were developed in the

mid-1960s by Briggs (1969) for industrial, ducted

emissions. These methods are still used today to estimate the plume rise and buoyancy of fires in spite of

the significant differences in characteristics between

ducted emissions and prescribed and wildland fires:

• Heat released from ducted sources is precisely

known and usually emitted at relatively constant rates during a single phase of combustion. Heat released from fires is a function of

fuel loading, fuel conditions, and ignition

method through several phases of combustion

(pre-ignition, flaming, smoldering, and residual), which create highly variable magnitudes and rates of heat release.

• Nearly all of the energy generated at the

source of a ducted plume is transmitted to

convection energy. In open burning, however,

significant amounts of energy are lost by conduction and radiation, reducing the amount of

available energy for convection.

• Plumes from ducted sources create single convective columns, but low intensity understory

burning that occurs over broad areas does not

develop a cohesive plume.

To improve plume rise predictions, emission production models need to do a better job of characterizing the

spatial and temporal pattern of heat release from

fires, and plume rise models need to be improved to

account for the energy lost from the convective system

through radiation and turbulent mixing. While models such as EPM and Burnup described in the previous

section simulate variable rates of heat release from

fires, both models use general estimates of spatial

distributions of fuel, including structure, composition,

and moisture content. Also, significant elements of

fires that influence convective energy — such as the

distribution of naturally piled fuel (“jackpots”), amount

and density of rotten fuel and duff, and release of

water vapor — are not adequately captured.

Rough approximations on the proportion of energy

available for convection were made more than 40 years

ago (Brown and Davis 1959). Despite efforts to improve

plume rise calculations by removing the density difference assumption (Scire and others 2000a), they

still are in use today.

Low intensity fires that typically do not have a

cohesive convective column must be treated, from a

modeling perspective, as an area source in Eulerian

grid models. In Lagrangian dispersion models, there is

currently no valid means of calculating plume rise

from unconsolidated convection. Eulerian coordinates

(used by box and grid models) are coordinate systems

that are fixed in space and time, and there is no

attempt to identify individual particles or parcels from

one time to the next. Lagrangian models (bell-shape or

Gaussian distribution pattern, often applied to plume

and puff models) are used to show concentrations

crosswind of the plume.

Another complication for modeling is that once

plumes from fires enter the atmosphere, their fluctuating convection dynamics make them more susceptible to erratic behavior than well-mannered industrial stacks. For example, different parts of a plume

can be carried to different heights in the atmosphere

at the same time. This causes unusual splitting patterns if there is a notable wind shear between lofted

elevations, causing different portions of the plume to

be transported in different directions. Therefore, predictions of the plume’s impact on visibility and air

quality under these conditions become highly uncertain (Walcek 2002). Even when the behavior of plumes

from fires resembles that of stack plumes, the varying

and widely distributed locations of wildland sources

prevent consistent study. For example, down-wash of

plumes has been observed from ducted (stack) emissions after an inversion breaks up — conditions that

are common at the end of an onshore breeze if the

plume is above the inversion at its source (de Nevers

2000; Venkatram 1988) or if horizontal stratification

in the lower atmosphere is disrupted by mountains (de

Nevers 2000).

These characteristics of plumes from fire are strikingly different than those of ducted industrial emissions yet little research has been done on this topic in

the past several decades.

Advection and Diffusion

In most existing models, the horizontal advection

of smoke and its diffusion (lateral and vertical spread)

are assumed to be controlled mainly by wind, and the

formation and dissipation of atmospheric eddies.

These elements are greatly simplified by assuming

constant wind (at least for an hourly time step) in

some cases (such as VSMOKE and SASEM), and a

Gaussian dispersion is nearly always imposed. Perhaps the most critical issues are the constantly changing nature of the plume due to scavenging, chemical

transformation, and changing convection dynamics

that affect plume transport.

Many photochemical and dispersion models depend on gridded meteorological inputs. Unfortunately,
38 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

numerical formulations of dynamic meteorological

models (for example, MM5: Grell and others 1995;

RAMS: Pielke and others 1992) do not adequately

conserve several important scalar quantities (Byun

1999a,1999b). Therefore, modelers often introduce

mass-conserving interpolations. For example, Models-3/CMAQ (Byun and Ching 1999) uses the MCIP

scheme (Byun and others 1999), Calpuff (Scire and

others 2000a) employs CALMET (Scire and others

2000b), and TSARS+ (Hummel and Rafsnider 1995)

is linked with NUATMOS (Ross and others 1988).

Driving a photochemical or dispersion model without

these mass-conserving schemes will produce inaccurate results, especially near the ground surface.

Scavenging

Smoke particles by nature of their small size provide

efficient cloud condensation nuclei. This allows cloud

droplets to condense around fine particles, called nucleation scavenging. Scavenging within a cloud also can

occur as particles impinge on cloud droplets through

Brownian diffusion, inertial impaction, or collision by

electrical, thermal, or pressure-gradient forces

(Jennings 1998). Cloud droplets eventually coalesce

into sizes large enough to precipitate out, thus removing smoke aerosols from the atmosphere. While

interstitial cloud scavenging, especially nucleation

scavenging, is thought to dominate the pollution

removal process, particles also may be removed by

impacting raindrops below a cloud. Jennings (1998)

reviews several theories on pollution scavenging but

contends that there is little experimental evidence to

support such theories.

The size and chemical structure of particles determine their efficiency in nucleation or other scavenging

mechanisms. While the chemical composition of smoke

is reasonably well known (see chapter 6), distributions

of particle size from fire are not. The few airborne

measurements (Hobbs and others 1996; Martins and

others 1996; Radke and others 1990) do not distinguish fire characteristics or combustion dynamics,

which play important roles in the range of particle

sizes emitted from a fire. Therefore, the efficiency of

scavenging biomass smoke particles out of the atmosphere by cloud droplets, rain, or other mechanism has

not been quantified.

Chemical Transformations

Chemical transformations provide another mechanism for changing particle and gas concentrations within

a plume. Chemical transformation in the plume can be

important in regional-scale modeling programs where

sulfate chemistry and ozone formation are of interest

(see chapter 6). Oxidation within the smoke plume

causes a loss of electrons during chemical transformation processes, which increases polarity of a molecule

and improves its water solubility (Schroeder and Lane

1988). This improves scavenging mechanisms by cloud

and rain droplets. Chemical transformation rates depend on complex interactions between catalysts and

environmental conditions such as turbulent mixing rates.

Transport and Dispersion

Models ________________________

Trajectories show the path of air parcels along a

streamline in the atmosphere. Their simplicity allows

trajectory methods to be used as a diagnostic tool for

identifying the origin of air parcels from a potential

receptor. This commonly is called a backward trajectory or back trajectory analysis. Because these models

integrate over time the position of a parcel of air that

is transported by wind, their accuracy is limited by the

grid resolution of the model. Also, the flow path of a

single parcel may have little relation to an actual

plume dispersion pattern.

Current models to predict trajectory or air quality

impacts from fires are inadequate in coverage and are

incomplete in scope (Sandberg and others 1999). But

because of new interest in modeling emissions on a

regional scale, land managers need transport and

dispersion models that include all fire and fuel types

as well as multiple sources. Such models need to be

linked to other systems that track fire activity and

behavior as well as provide for variable scaling to fit

the area of interest. At the operational level, models

that support real-time decisionmaking during fire

operations in both wildland fire situation analysis and

go/no-go decision making are also needed (Breyfogle

and Ferguson 1996). Transport and dispersion models

fall into four major categories. These categories include plume, puff, particle, and grid.

Plume Models

One of the simplest ways of estimating smoke concentrations is to assume that plumes diffuse in a

Gaussian pattern along the centerline of a steady wind

trajectory. Plume models usually assume steady-state

conditions during the life of the plume, which means

relatively constant emission rates, wind speed, and

wind direction. For this reason, they can be used only

to estimate concentrations relatively near the source

or for a short duration. Their steady-state approximation also restricts plume models to conditions that do

not include the influence of topography or significant

changes in land use, such as flow from a forest to

grassland or across a land-water boundary.

Gaussian plume models have a great benefit in places

and circumstances that restrict the amount of available

input data. They can be run fast and have simple but

realistic output that can be easily interpreted. Many
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 39

regulatory guidelines from the EPA are based on

Gaussian plume models.

Plume models typically are in Lagrangian coordinates that follow particles or parcels as they move,

assigning the positions in space of a particle or parcel

at some arbitrarily selected moment. (Lagrangian

coordinates are used by plume, puff, and particle

models.) Examples adapted for wildland biomass smoke

include VSMOKE (Harms and others 1997; Lavdas

1996) and SASEM (Riebau and others 1988; Sestak

and Riebau 1988). Both models follow regulatory guidelines in their development and offer a simple screening

tool for examining potential concentrations at receptor locations from straight-line trajectories relatively

near the source. However, SASEM directly compares

downwind concentrations with ambient standards and

calculates visibility impairment in a simple manner.

It is also used as a State regulatory model in Wyoming,

Colorado, New Mexico, and Arizona, and has been

recommended for use by the EPA.

Plume rise models developed for other applications

might be useful if adapted to fire environments. For

example, ALOFT-FT (A Large Outdoor Fire Plume

Trajectory Model - Flat Terrain), developed for oil-spill

fires (Walton and others 1996), is a computer-based

model to predict the downwind distribution of smoke

particulate and combustion products from large outdoor fires. It solves the fundamental fluid dynamic

equations for the smoke plume and its surroundings

with flat terrain. The program contains a graphical

user interface for input and output, and a database of

fuel and smoke emission parameters that can be

modified by the user. The output can be displayed as

downwind, crosswind, and vertical smoke concentration contours.

Puff Models

Instead of describing smoke concentrations as a

steadily growing plume, puff models characterize

the source as individual puffs being released over

time. Each puff expands in space in response to the

turbulent atmosphere, which usually is approximated as a Gaussian dispersion pattern. Puffs move

through the atmosphere according to the trajectory

of their center position. Because puffs grow and

move independently of each other, tortuous plume

patterns in response to changing winds, varying

topography, or alternating source strengths can be

simulated with some accuracy.

Some models allow puffs to expand, split, compact,

and coalesce (Hysplit: Draxler and Hess 1998; Calpuff:

Scire and others 2000a) while others retain coherent

puffs with constantly expanding volumes (NFSpuff:

Harrison 1995). In either case, the variability of puff

generation, movement, and dispersion does not restrict the time or distance with which a plume can be

modeled. Most puff models are computed in Lagrangian

coordinates that allow accurate location of specific

concentrations at any time.

Particle Models

In a particle model, the source is simulated by the

release of many particles over the duration of the burn.

The trajectory of each particle is determined as well as

a random component that mimics the effect of atmospheric turbulence. This allows a cluster of particles to

expand in space according to the patterns of atmospheric turbulence rather than following a parameterized spatial distribution pattern, such as common

Gaussian approximations. Therefore, particle models

tend to be the most accurate way of simulating concentrations at any point in time. Because of their numerical complexity, however, particle models usually are

restricted to modeling individual point sources with

simple chemistry or sources that have critical components such as toxins that must be tracked precisely.

Particle models use Lagrangian coordinates for accurate depiction of place of each time of particle movement (for example, Hysplit: Draxler and Hess 1998;

PB-Piedmont: Achtemeier 1994, 2000).

Grid Models

Grid models use Eulerian coordinates, disperse pollutants uniformly within a cell, and transport them to

adjacent cells. The simplicity of advection and diffusion in a grid model allows these models to more

accurately simulate other characteristics of the pollution, such as complex chemical or thermal interactions, and to be used over large domains with multiple

sources. This is why grid models commonly are used

for estimating regional haze and ozone and are often

called Eulerian photochemical models. Much of the

future work on fire impact assessment and planning at

regional to national scales will be done by using grid

models.

Because of their nature, grid models are not used to

define accurate timing or locations of pollutant concentrations from individual plumes, only concentrations that fill each cell. This means that sources

small relative to the grid size, which create individual

plumes, will introduce unrealistic concentrations in

places that are outside of the actual plume. Ways of

approximating plume position and its related chemical stage include nesting grids to finer and finer

spatial resolutions around sources of interest (Chang

and others 1993; Odman and Russell 1991), establishing nonuniform grids (Mathur and others 1992),

and creating “plume-in-grid” approximations (Byun

and Ching 1999; Kumar and Russell 1996; Morris

and others 1992; Myer and others 1996; Seigneur and

others 1983).
40 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Many regional haze assessments use the Regulatory

Modeling System for Aerosols and Acid Deposition

(REMSAD) (Systems Applications International 2002).

This model was adapted from the urban airshed model–

variable grid (UAMV) by removing its plume-in-grid

feature and parameterizing explicit chemistry to improve computational efficiency. REMSAD incorporates

both atmospheric chemistry and deposition processes

to simulate sulfate, nitrate, and organic carbon particle formation and scavenging. As such, it is quite

useful for simulations over large regions.

The Models-3/ CMAQ modeling system is designed

to integrate the best available modules for simulating

the evolution and dispersion of multiple pollutants at

a variety of scales (Byun and Ching 1999). It includes

chemical transformations of ozone and ozone precursors, transport and concentrations of fine particles

and toxics, acid deposition, and visibility degradation.

At the other end of the grid modeling spectra are

simple box models that describe pollution characteristics of a small area of interest. Box models instantaneously mix pollutants within a confined area, such as

a valley. This type of model usually is restricted to

weather conditions that include low wind speeds and

a strong temperature inversion that confines the mixing height to within valley walls (Lavdas 1982; Sestak

and others 1988). The valley walls, valley bottom, and

top of the inversion layer define the box edges. The end

segments of each box typically coincide with terrain

features of the valley, such as a turn or sudden elevation change. Flow is assumed to be down-valley, and

smoke is assumed to instantaneously fill each box

segment. Few box models include the complex chemical or particle interactions that are inherent in larger

grid models.

Model Application _______________

Modeling of the transport and dispersion of industrial stack plumes has occurred for decades, prompting a variety of techniques. But application to fires is

much more limited (Breyfogle and Ferguson 1996).

Part of the reason for this is that source strength from

undulating and meandering fires is so difficult to

simulate accurately. Therefore, applications have been

appropriate mainly for relatively homogeneous

fuelbeds and steady state burn conditions. This has

restricted most transport and dispersion modeling to

fires on a local scale and to those started in harvest

residue from land clearing operations where fuels are

scattered uniformly over the landscape or collected

into piles (Hardy and others 1993; Hummel and

Rafsnider 1995; Lavdas 1996; Sestak and Riebau

1988). Global-scale modeling also has taken place

where fuelbed and ignition patterns are assumed to be

approximately steady state in relation to the grid size

(Kasischke and Stocks 2000; Levin 1996).

Gaussian plume models (Harms and others 1997;

Lavdas 1996; Sestak and Riebau 1988; Southern Forest Fire Laboratory Personnel 1976) are useful for

places with relatively flat terrain, for circumstances

when input data are scarce, and for evaluating surface

concentrations relatively near the source. These models typically require only an estimate of atmospheric

stability, trajectory wind speed and direction, and

emission rates. Fires are modeled independently.

Therefore, accumulations of smoke from multiple fires

are ignored. Some Western States require SASEM

modeling of prescribed burns before they can be permitted (Battye and Battye 2002).

Puff models (Draxler and Hess 1998; Harrison 1995;

Hummel and Rafsnider 1995; Scire and others 2000a)

are needed when simulating long-range transport, or

transport that occurs during changeable environmental conditions such as influences from complex terrain

or variable weather. NFSpuff has an easy user interface, but because of its internal terrain data files it is

restricted to applications in the Western States, excluding Alaska (Harrison 1995). Hysplit (Draxler and

Hess 1998) currently is programmed to accept only 16

individual sources and assumes a constant rate of

emissions with no plume rise. Hysplit (Draxler and

Hess 1998) and Calpuff (Scire and others 2000a) both

include simple chemistry. NFSpuff is the most commonly used puff model for prescribed fire planning

(Dull and others 1998). All three models are linked to

the MM5 meteorological model (Grell and others 1995).

NFSpuff can function with a simple trajectory wind,

and Hysplit and Calpuff can accept other gridded

weather input data.

Particle models are used in coupled fire-atmosphere

modeling (Reisner and others 2000) and for tracking

critical signature elements (Achtemeier 1994, 2000;

Draxler and Hess 1998). The sophistication of these

types of models and their computational requirements,

however, has thus far limited their application to

research development or individual case studies.

Eulerian photochemical grid models are highly useful in estimating smoke concentrations from many

sources over large domains. In addition, their ability

to model secondary chemical reactions and transformations is needed for determining ozone concentrations and regional haze conditions. Regional planning

organizations such as the Western Regional Air Partnership (WRAP), are evaluating the photochemical

models Models-3/CMAQ (Byun and Ching 1999) and

REMSAD (Systems Applications International 2002)

for use in guiding State implementation plans (SIPs)

and Tribal implementation plans (TIPs).

Additional work is needed to fill critical gaps in the

modeling systems identified above. As the need for
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 41

Traditionally, ozone and secondary aerosol precursors have been discussed within the context of urban

smog caused by auto exhaust and reactive organic

compounds emitted from industrial facilities. But the

same pollutant and tropospheric chemical reactions

occur in both urban settings and in rural areas where

wildfire smoke may be an important if not dominant

source of ozone precursor emissions. In these situations, emissions from fire may play an important role

in ozone formation as well as nitrate and, indirectly,

sulfate aerosol formation, which results in visibility

impairment and increased PM2.5 concentrations.

At present, there is an urgent need to understand

the impact of fire emissions on emerging visibility and

ambient air standards as they relate to fire planning

at the strategic, programmatic, and operational scales

(Fox and Riebau 2000; Sandberg and others 1999).

Chemical processes that occur in plumes from fires,

directly or indirectly, touch on a number of these

issues and are critical to the development of a regional

model that will be used to assess the impact of fire on

air quality.

Because of the Environmental Protection Agency’s

(EPA) pressing regulatory need to assess inter-State

ozone transport and sources of precursor emissions, a

new regional-scale mechanistic model called Models3/CMAQ (Byun and Ching 1999) is being used by the

Ozone Transport Commission (OTC) region of NorthChapter 6: Atmospheric and

Plume Chemistry

eastern and Mid-Western States, and the Western

Regional Air Partnership (WRAP). Future applications will likely involve regional haze modeling in

other areas of the country. Oxides of nitrogen (NOX)

and volatile organic compounds (VOCs) emissions

from fire in the OTC have not previously been considered significant, but the new model photochemistry

module requires that precursor emissions be included

for all sources. As Models-3/CMAQ develops, NOX and

VOC emissions from fire will be included in ozone and

secondary modeling.

Ozone Formation in Plumes_______

Field observations of ozone formation in smoke

plumes from fires date back nearly 25 years when

aircraft measurements detected elevated ozone at the

edge of forest fire smoke plumes far downwind (Stith

and others 1981). More recent observations (Wotawa

and Trainer 2000) suggest that high concentrations of

ozone are found in forest fire plumes that are transported great distances and across international boundaries. Measurements made during EPA’s 1995 Southern Oxidant Study indicate that Canadian forest fires

changed the photochemical properties of air masses

over Tennessee on days with strong fire influence.

Regional background ozone levels were elevated by 10

to 20 ppb on fire impact days as compared with
42 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

nonimpact days during the study. Aircraft measurements found that, although forest fire plumes were

always well defined with respect to carbon monoxide,

they gradually lost their definition with respect to

ozone after being mixed into the boundary layer. The

amount of ozone transported to the surface measurement sites was found to depend upon where and when

the plumes reached the ground. Elevated plumes were

always marked by enhanced ozone concentrations, at

times reaching values of 80 to 100 parts per billion

(ppb) above tropospheric background.

Stith and others (1981) mapped ozonemixing ratios

in an isolated, fresh, biomass-burning plume. At the

source, or near the bottom, of the horizontally drifting

plume they measured low or negative changes in ozone

values, which they attributed to titration by NO and

low ultraviolet (UV) intensity. Near the top of the

plume, 10 km downwind, and in smoke less than 1

hour old, they measured change in ozone values as

high as 44 parts per billion by volume (ppbv). Greater

changes in ozone were positively correlated with high

UV. Thus the initial destruction of ozone by reactive

species in the plume followed by its gradual formation

was documented.

A new and potentially useful tool for assessing

impacts of long-range plume transport is based on the

concept of using ∆O3/∆CO (excess O3 over excess CO)

as a “photochemical clock” to denote the degree of

photochemical processing in a polluted air mass by

using carbon monoxide as a stable plume signature.

As the plume disperses, its volume expands and absolute values of ozone can drop even though net production of ozone is still occurring. The ∆O3/∆CO normalizes for plume expansion and is a useful measure of net

ozone production. In the course of atmospheric chemistry research, numerous observations of ∆O3/∆CO

ratios have been made in biomass burning haze layers.

Unfortunately, the observations represent haze of

various ages and uncertain origin. In haze layers 1 to

2 days old, changes in the ∆O3/∆CO ratios of 0.04 to

0.18 were measured over Alaska (Wofsy and others

1992) and ratios of 0.1 to 0.2 were measured over

Eastern Canada (Mauzerall and others 1996). High

ratios, up to 0.88, were measured at the top of haze

layers that had aged about 10 days in the tropics

(Andreae and others 1994).

In 1997, airborne Fourier transform infrared spectroscopy (FTIR) measurements in large isolated biomass

burning plumes in Alaska revealed new details of

downwind chemistry. Downwind smoke samples that

had aged in the upper part of one plume for 2.2 ± 1

hours had ∆O3/∆CO ratios of 7.9 ± 2.4 percent, resulting from initial, absolute ozone formation rates of about

50 ppb/hr. Downwind samples obtained well inside

another plume, and of similar age, did not have detectable ∆O3, but did have ∆NH3/∆CO ratios about onethird of the initial value. ∆HCOOH/∆CO (formic acid)

and ∆CH3COOH/∆CO (acetic acid) usually increased

about a factor of 2 over the same time scale in samples

from both plumes. NOX was below the detection limit

in all the downwind samples. These data provided the

first precise in-plume measurements of the rate of

O3/CO increase and suggested that this rate depended

on relative position in the plume. The apparently

rapid disappearance of NOX is consistent with the

similar early observation, and the drop in NH3 was

consistent with a reaction with HNO3 to form ammonium nitrate, which is a NOX sink. Secondary sources

of formic acid relevant to polluted air have been

described (Finlayson-Pitts and Pitts 1986). Jacob and

others (1992, 1996) discussed several gas-phase sources

of acetic acid that could occur in biomass burning

plumes. These experiments provide the first experimental indication of the approximate time scale of

secondary organic acid production in actual plumes.

A large number of photochemical modeling studies

of biomass burning plumes have been published

(Chatfield and Delaney 1990; Chatfield and others

1996; Crutzen and Carmichael 1993; Fishman and

others 1991; Jacob and others 1992, 1996; Koppmann

and others 1997; Lee and others 1998; Lelieveld and

others 1997; Mauzerall and others 1998; Olson and

others 1997; Richardson and others 1991; Thompson

and others 1996). Nearly all these studies conclude

that the net production of ozone occurs either in the

original plume, or as a result of the plume mixing with

the regional atmosphere. Several studies have shown

a strong dependence of the final modeled results on the

details of the post-emission-processing scenario such

as the timing between production of the emissions and

their convection to the free troposphere (Chatfield and

Delaney 1990; Jacob and others 1996; Lelieveld and

others 1997; Pickering and others 1992; Thompson

and others 1996).

Factors Affecting Plume

Chemistry______________________

The specific chemical composition of the plume depends on many factors: the details of post-emission

atmospheric reactions including dilution rates, photolysis rates, position within the plume, altitude, and

smoke temperature, which varies by time of day and

combustion stage. Equally important is the chemistry

of the downwind air that mixes with the plume, which

could be clean air or contain aged plumes from urban

areas or other fires. In addition, the physical aspects of

the plume mixing are important. For example, at the

relatively low temperatures typical of higher altitudes

in the troposphere, peroxyacetyl nitrate (PAN) is a

stable molecule, which can be transported. At lower

altitudes, PAN can thermally decompose and rerelease

NOX. Nitric acid (HNO3) can also be an important,
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 43

transportable reservoir species for NOX at high altitudes but for a different reason. HNO3 has a narrower

absorption cross-section at lower temperatures and

therefore is less susceptible to photolysis. The rate of

bimolecular reactions among smoke components usually decreases with temperature (thus typically with

altitude or at night). Reaction rates depend even more

strongly on the dilution rate, at least initially. Dilution

by a factor of 2 will decrease a bimolecular reaction

rate by a factor of 4.

Emission Factors for Reactive

Species________________________

Emission factors for hydrogen oxide (HOX, a collective term for OH and HO2) precursors, NH3, and NOX

have been estimated with the Missoula, MT, open-path

spectroscopic system (Yokelson and others 1997). These

experiments reveal that smoke contains high levels of

oxygenated organic compounds, methanol (CH3OH),

acetic acid (CH3COOH), and formaldehyde (HCHO).

These compounds typically oxidize or photolyze within

hours in a smoke plume to release HOX that is important in sulfate aerosol formation processes. Under

clear-sky conditions typical for noon on July 1 at 40°N

latitude, the formaldehyde photolysis lifetime is about

3.8 hours (Yokelson and others 1997). Since the

HCHO/CO source ratio for fires is typically near 2

percent, this process clearly injects large quantities of

HO2 into fresh plumes (Yokelson and others 1997).

HOX emissions from fire may become a critical input to

regional haze models that simulate secondary sulfate

formation processes.

The H2O2 is soluble in cloud droplets where it would

play a major role influencing reaction rates during

aqueous-phase sulfate formation chemistry (NRC

1993).

Particle Formation in Plumes______

A number of processes are important in plume particle formation and growth. Many of these processes

involve interaction with the trace gases in a plume

originating from nucleation in which two gases react

to form a solid nucleus for subsequent particle growth.

An example of nucleation is the reaction of ammonia

and nitric acid. In addition, condensation can create

new particles when gases cool or through particle

growth when a trace gas collides with and condenses

on an existing particle. The second condensation process is quite common because biomass burning aerosol

is hydrated. Soluble nucleilike ammonium nitrate

promotes this process. There is a little evidence that

organic gases also condense on particles. Nucleation

and condensation are both examples of trace-gas-toparticle conversion, which will increase the mass of

particles in a plume, decrease the concentration of

certain trace gases in the plume, and, in the case of

condensation, contribute to an increase in average

particle diameter. Andreae and others (1988) measured particle-NH4

+

/CO2 ratios of 0.7 to 1.5 percent in

slightly aged biomass burning plumes. Measurements

of NH3/CO in fresh smoke are typically near 2 percent.

Thus, there is probably rapid conversion of gas-phase

NH3 to particle NH4

+ either through nucleation or

dissolution in the surface water of other hydrated

particles.

Coagulation is when two particles collide and combine. This increases the average particle diameter,

reduces particle number, and does not effect total

particle mass. Coagulation probably contributes to the

increase in average particle diameter that occurs downwind from fires (Reid and others 1998).

At any given point in its evolution a particle may

impact the trace gas chemistry in a smoke plume. For

instance, it is known that NO2 reacts on the surface of

soot particles to yield gas phase HONO. This and other

heterogeneous reactions such as ozone destruction

may occur on smoke aerosol. Some recent research

suggests that oxygenated organic compounds emitted

from fires could also be important in heterogeneous

processes. Hobbs and Radke (1969), Desalmand and

others (1985), Andreae and others (1988), and Roger

and others (1991) found that a high percentage (25 to

100 percent) of fire aerosol particles from fires could be

active as condensation nuclei (CCN). Radke and others (1990) observed that cumulus clouds greater than

2 km in depth scavenged 40 to 80 percent of smoke

particles. The high concentrations of CCN in smoke

plumes can contribute to the formation of clouds with

smaller than “normal” cloud droplet size distributions.

This type of cloud is more reflective to incoming solar

radiation and less likely to form precipitation. Some

work suggests that absorbing aerosol can reduce cloud

formation. Finally, clouds can evaporate and leave

behind chemically altered particles.

All of these mechanisms alter both the chemical

nature and number of particles contained within smoke

plumes from fires. In addition, reactive species emitted from fires (see previous section) may alter the

conversion rate of gaseous precursors of secondary

sulfate and nitrate particles, affecting regional haze

modeling results.

Although the regulatory implications of reactive species emissions from fire are yet to be determined, much

more attention to these issues will occur once fire is

including in regional haze and ozone modeling efforts.
44 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Notes

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 45

Chapter 7: Estimating the Air

Quality Impacts of Fire

State-of-the-science methods used to determine the

impact of fire on air quality and visibility include: (1)

emission inventories; (2) air quality monitoring instruments to measure smoke concentrations in realtime; and (3) filter-based monitoring techniques and

receptor-oriented methods that quantify wildfire smoke

contribution to air pollution based on the chemical

characteristics of smoke particles or the spatial and/or

temporal variability. Fire also contributes to groundlevel ozone. These topics have become increasingly

important to both air quality regulators and land

managers as efforts to identify, or apportion, the

contributions that fire makes to particulate air pollution, regional haze, and ground-level ozone come under increased scrutiny.

Because the health effects of air pollution are so

difficult to measure in the broad population, there has

been little effort to regulate or manage those effects

directly. Many smoke management decisions are made

on the basis of nuisance complaints as an indicator,

rather than on quantitative measurements of impacts

to health and welfare. Close to the source, efforts are

being made to keep the exposure of firefighters to

hazardous air pollutants within the standards set by

the Occupational Safety and Health Administration.

Hazard assessment describes the nature, concentration, and duration of pollutants. Exposure assessment

quantifies the population exposed and the degree of

exposure. Risk assessment describes the probable

result for a population from all exposures. Integrated

health risk assessments and economic assessments

are still rare.

Modeling and data systems are needed to predict,

measure, and monitor the ultimate effects of air pollution from fires on human or ecosystem health, on the

economy, and on the comfortable enjoyment of life and

property. Risk assessment methods are needed to

compare these effects with those from other sources.

Emission Inventories ____________

An emission inventory is an estimate of the mass of

emissions by class of activity within a specified geographic area in a specified amount of time. Usually, an

inventory is compiled by multiplying the appropriate

emission factor (see chapter 4) by the estimated level

of activity (in other words, tons of fuel consumed).

Development of emission inventory methods for

fires was recently reviewed in detail by Battye and

Battye (2002). The report considers prior attempts at

emission inventory, describes approaches to estimating emissions from fires, and reviews the scientific

information available as components of an inventory.

The report also reviews emission reduction strategies

and smoke management techniques.
46 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

An emission inventory provides an understanding

of the relative burden on the air resource from particular air pollution source categories. Emission inventories help explain the contribution of source

categories to pollution events, provide background

information for air resource management, provide

the means to verify progress toward emission reduction goals, and provide a scientific basis for State air

program development. An accurate emission inventory provides a measured, rather than perceived,

estimate of pollutant production as the basis for

regulation, management action, and program compliance. Emission inventories should include all important source categories including mobile, area, and

stationary, and the inventories are not complete

unless difficult-to-quantify sources such as agricultural burning, backyard burning, rangeland burning, and wildland and prescribed burning are addressed. Emission inventories are a basic requirement

of State air resource management programs and are

a required element of State implementation plans

(SIPs). Emission inventories are also compiled annually at the national level and for specific geographic

regions (sub-State, multi-State, or multi-jurisdiction) to address a particular regional air quality

issue.

The science necessary to accurately estimate emissions from prescribed burning is quite good for most

fuel types in the United States if good quality information about several critical variables is known. Area

burned, fuel type, fuel loading, fuel arrangement, fuel

consumption, and emission factors are all needed to

accurately estimate emissions. Some of these require

onsite reporting for reasonable accuracy including

area burned, fuel type, and fuel arrangement. Other

factors can be defaulted or estimated with reasonable

accuracy if some other information is known. Fuel

loading can be defaulted with knowledge of the fuel

type and arrangement. Fuel consumption can be calculated with knowledge of the fuel type, fuel loading,

and fuel moisture. Emission factor assignment is made

with knowledge of the fuel type.

The science of predicting emissions from wildland

fire is much weaker than for prescribed fire. In addition, it is generally far more difficult to obtain decent

quality information about individual wildland fires.

In most cases, the information gap that makes fire

emissions prediction a difficult endeavor is good quality, consistent, and regular reporting of the specific

onsite variables needed for emissions estimation. Data

collection systems that are supported and utilized by

fire managers need to be developed for every State

where a reasonable estimate of prescribed fire emissions is desired. Data collection for wildfire emissions

estimation will be more difficult because some of the

needed information is not currently available in a way

that is compatible with emissions estimation requirements. For example, a single wildfire often burns

through many different fuel types, but current reporting requirements request the fuel type at the point of

ignition. This fuel type may or may not be representative of the majority of acres burned in the wildfire.

Also, acres burned in wildland fires may be the area

within the fire perimeter rather than the actual acres

blackened by fire as is needed for emissions estimation. Similarly, the area reported as burned in prescribed fires is often the area authorized for burning

whether or not the entire burn was completed.

State Emission Inventories

High quality Statewide inventories of daily emissions from prescribed fire have been developed by

Oregon and Washington since the 1980s (Hardy and

others 2001). Eleven other States (Alabama, Alaska,

Arizona, California, Colorado, Florida, Idaho, Montana, Nevada, South Carolina, and Utah) estimate

annual prescribed fire emissions from records of acreage burned by fuel type and fuel loading at the end of

the burning season. Many other States (such as Michigan, New Mexico, and Tennessee) currently have no

annual reporting program.

No State has a reporting system for wildland fires

that is based on actual, reported data from individual

wildland fires events. Any estimate a State may have

of wildland fires emissions is based on gross assumptions about fuel loading and consumption, and on an

area-burned figure that may systematically overestimate the true value.

Regional Emission Inventories

Several recent regional inventories compiled in

support of regional haze program development have

shown new approaches to fire emission inventory

development.

The Fire Emissions Project (FEP) calculated an

emissions inventory for 10 Western States for a current year (1995) using actual reported data, plus two

future years (2015 and 2040) using manager projections of fire use. Fourteen vegetative cover types were

chosen to characterize the range of species types within

the 10-State domain. Within each vegetative cover

type, up to three fuel loading categories (high, medium, and low) could be specified by field fire managers. Fuel consumption calculations relied on expert

estimates of fuel moisture believed to be most frequently associated with a particular type of burning.

Emission factors were assigned based on the vegetative cover type. The FEP inventory was used during

the Grand Canyon Visibility Transport Commission

(GCVTC) effort to apportion sources of visibility impairment in the Western States.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 47

The GCVTC also sponsored the development of a

wildland fire emissions inventory for the period 1986

through 1992. The GCVTC wildfire inventory included

only wildland fires greater than 100 acres in size

(capturing approximately 98 percent of the acreage

burned). The variability of wildland fire emissions,

which ranged from 50,000 tons per year of PM2.5 to

more than 550,000 tons per year over the 7 years

studied, indicates the difficulty in selecting a single 1

year period that is representative of “typical” fire

emissions (GCVTC 1996a).

In 1998, analysts at the Forest Service’s Missoula

Fire Sciences Laboratory, Rocky Mountain Research

Station, used the FEP management strategies with

new, additional data to estimate emissions from wildland fires in the Western States (Hardy and others

1998). This inventory of potential emissions used a

suite of new or improved spatial data layers, including

vegetation/cover type, ownership, fuel and fire characteristics, modeled emissions and heat release rates,

and fuels treatment probability distributions. These

inventories are included in the Environmental Protection Agency’s (EPA) National Emission Inventory

(NEI).

Wildland fire frequency and occurrence are highly

variable in time and space (fig. 7-1). The impact of

wildland fire smoke on Class I area visibility is also

expected to be highly variable from year to year with

episodic air quality and visibility impact events that

are difficult to predict. Seasonal impacts may be many

times higher than annual averages.

National Emission Inventories

National emission inventories for prescribed fire

have been compiled and reported by several investigators (Chi and others 1979; Peterson and Ward 1992;

Ward and others 1976; Yamate and others 1975). Of

these, only the Peterson and Ward inventory of particulate matter and air toxic emissions from prescribed fires during 1989 is still useful today, despite

the inconsistencies in the information available to

compile the emission estimates. The poor data collection and inconsistent or nonexistent reporting systems in use at the time of the 1989 inventory continue

today.

Improving Emission Inventories

Significant barriers to compiling better regional

inventories include:

• Varying degrees of availability and number of

records describing burning activity over multiple States, multiple agencies, ownerships,

and Tribes.

• Lack of a national wildland fuel classification

system with spatial attributes.

• Limited and inappropriate modeling of fuel

consumption and emission characterization

for prescribed burning in natural fuels.

Sandberg and others (1999) describe remedies to

overcome some of the limitations of data collection and

availability. These remedies are intended to guide

Figure 7-1—Number of acres burned by wildfire between 1960

and 2000 (National Interagency Fire Center 2002).
48 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

future inventory development efforts. Significantly,

these remedies include adoption of standardized burn

reporting protocols to be used by all agencies, Tribes,

and ownerships to report daily emissions for each

burn, location of the burn, and many other parameters.

The Fuel Analysis, Smoke Tracking, and Report

Access Computer System (FASTRACS) is a sophisticated system developed by the Forest Service and

Bureau of Land Management in the Pacific Northwest. FASTRACS tracks all the information needed

for accurate estimation of emissions from Federal use

of prescribed fire in Washington and Oregon including

the ability to track use of emission reduction techniques. As long as field fire managers are doing a

reasonable job of reporting the information required

by FASTRACS, this system provides excellent emissions calculation capabilities and the best data reporting standards in the country. Currently other landowners, such as State and private, are not using

FASTRACS in Washington and Oregon although there

is an effort under way to bring them into the system.

FASTRACS is also being looked at by other regions

and may be adopted or emulated across the country.

For more information about FASTRACS, see http://

www.fs.fed.us/r6/fastracs/index.htm.

Another data reporting system is under development in California. The Prescribed Fire Information

Retrieval System (Cal/PFIRS) is a centralized electronic database that allows all users immediate access

to detailed information on burns on a day-to-day basis.

Cal/PFIRS does not include the kind of detailed reporting of information that could be used to assess

the use of emission reduction techniques but does

provide a reasonable estimate of the amount of burning taking place. For more information on Cal/PFIRS,

see http://www.arb.ca.gov/smp/progdev/techtool/pfirs.htm.

Research since about 1970 has significantly improved the completeness and accuracy of emission

inventory techniques. However, the science is being

pressed forward because of new demands for regional

scale emission transport information needed to assess

the impact of wildland smoke on PM2.5 air quality

standards and regional haze. Because of new air regulatory demands, emission inventories, when used in

concert with regional models, have become an important means of apportioning fire smoke impacts on air

resources.

Air Quality Monitoring ___________

Unlike emission inventories, air quality monitors

determine actual pollutant loading in the atmosphere

and are therefore the most direct measure of air

quality on which air regulatory programs are based.

Samples of particulate matter in the atmosphere (PM10

or PM2.5, or both) are also used for source apportionment purposes to identify the origin of the aerosols.

Monitoring of smoke from fires, however, presents

several unusual technical challenges that affect results. These challenges center on the fact that smoke

from fires has several unique characteristics.

Current Monitoring Techniques

The three principal methods of measuring air pollution are samplers, optical instruments, and electrochemical devices. Samplers are most common for longterm monitoring. Data from optical meters and

electrochemical devices can be stored in a computer or

datalogger on site or transmitted from remote locations to provide real-time information.

Samplers—Samplers collect aerosols on a filter or

chemical solution. A simple gravimetric measure of

mass concentration may be obtained, or different types

of filters or solutions can be used, to help define

chemical species and particle sizes. For chemical speciation, filters must be sent to a laboratory for analysis. For this reason, sampling information usually is

delayed by days to weeks after the sampling period.

Active samplers are the most accurate as they use a

pump to pass a known volume of air through the

collector. Passive samplers are the least expensive,

allowing air to reach the collector by some physical

process such as diffusion. Tapered Element Oscillation Microscales (TEOMs) are a special class of samplers that provide a gravimetric measure of mass

concentration at the studied site without having to

transport filters to a laboratory.

All sampling devices lose some degree of semivolatile

fine particulates (Eatough and Pang 1999). Positive

and negative organic carbon artifacts are just two of

several factors that contribute to variability between

different colocated instruments. To minimize this

variability, consistent sampling methods are used

throughout a sampling network to help recognize

such artifacts.

The analytical technique used to quantify carbon

concentrations from filters also can cause discrepancies between measurements (Chow 2000). For example, the NIOSH 5040 method (Cassinelli and

O’Conner 1994) is a thermal-optical transmittance

method of speciating total, organic, elemental, and

carbonate (inorganic) carbon being adopted by the

EPA’s PM2.5 program. This method is a departure

from the thermal-optical reflectance method that has

been used in the IMPROVE program. Recent comparisons between ambient samples have identified differences as great as 17.5 ± 15 percent (EPA 2000a), which

can be significant when monitoring for National Ambient Air Quality Standards (NAAQS) violations.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 49

Because filters can become overfull, they must be

changed regularly and are not suitable for sites close

to fires where particulate concentrations are heavy.

Optical Instruments—Optical instruments use a

light source to measure the atmosphere’s ability to

scatter and absorb light. Common devices are photometers, which measure the intensity of light, and transmissometers, which are photometers used to measure

the intensity of distant light. Photometers and transmissometers have a direct relation to visual range.

Nephelometers measure the scattering function of

particles suspended in air. They can be used to determine the visual range, as well as the size of the

suspended particles, by changing the wavelength of

the light source. Wavelengths of 400 to 550 nm are

common for monitoring smoke from biomass fires,

while wavelengths of 880 nm are more common for

road dust measurements. Because the instruments

have increasing application for both long-term and

real-time monitoring of smoke, Trent and others (2000)

evaluated the accuracy of several different optical

instruments by comparing their output to gravimetric

samples.

Investigators have found some problems in field

reliability and temperature drift among photometers

and nephelometers (Trent and others 1999, 2000).

While Davies (2002) recommends a general coefficient

for relating scattering coefficient to drift smoke from a

DataRAM nephelometer, a precise relation between a

nephelometer’s measured scattering coefficient and

particle concentration depends on the wavelength of

the instrument and the particle distribution of the

medium, which varies by combustion stage and fuel

type.

Electrochemical Devices—Electrochemical devices have been used in industrial applications for

many years. Their small size and ability to measure

criteria pollutants, such as carbon monoxide, make

them suitable for personal monitoring or monitoring

in extremely remote locations. Thus, they are gaining

value for monitoring wildland smoke impacts. For

example, Reinhardt and Ottmar (2000) recommend

the use of an electrochemical dosimeter for monitoring

exposure levels experienced by wildland fire fighters

(Reinhardt and Ottmar 2000).

States, Tribes, and local air agencies use a variety of

instruments to monitor long-term and real-time smoke

impacts for both NAAQS and visibility to suit their

local interests and regulatory needs. The Interagency

Monitoring of Protected Visual Environments (IMPROVE) program is one of few nationally coordinated

monitoring projects.

IMPROVE was established in 1985 in response to

the 1977 amendment of the Clean Air Act requiring

monitoring of visibility-related parameters in Class I

areas throughout the country (fig. 7-2). The IMPROVE

network uses a combination of speciation filters on

active samplers to measure physical properties of

atmospheric particles (PM2.5 and PM10) that are

related to visibility. Many sites also include transmissometers and nephelometers optical devices. Also,

cameras are used document the appearance of scenic

vistas. Because the samplers collect for 24 hours every

3 days, their information is used for determining longterm trends in visibility. The optical and camera

devices can monitor more frequently and can help

define short-term or near real-time changes in visibility impact

Source Apportionment ___________

Most air monitoring programs are designed to measure particulate mass loading to provide data for

PM10 and PM2.5 NAAQS and visibility. Because

these sizes of particles can come from many sources,

they are not useful for apportioning to one source or

another. While the IMPROVE program provides speciated aerosol data that are helpful in source attribution analysis, the averaging periods of samples and

sparse location of sites make IMPROVE measurements difficult to use for source attribution without

supplemental measurements or modeling tools.

Wotawa and Trainer (2000) found that 74 percent of

the variance in the average afternoon carbon monoxide levels could not be attributed to anthropogenic

sources during the 1995 Southern Oxidant Study

(Chameides and Cowling 1995). Analysis of weather

patterns indicated that transport of wildland fire

smoke from Canada could explain the elevated carbon

monoxide levels. Also, they discovered a statistically

significant relationship between the elevated carbon

monoxide and ground-level ozone concentrations.

Characterization of organic carbon compounds found

within the organic carbon fraction of fine particulate

matter coupled with inclusion of gaseous volatile organic compounds (VOCs) holds substantial promise in

advancing the science of source apportionment (Watson

1997). The key to the use of chemical mass balance

methods is the acquisition of accurate data describing

the chemical composition of both particulate matter

and VOCs in the ambient air and in emissions from

specific sources. Several organic compounds unique to

wood smoke have been identified including retene,

levoglucosan, thermally altered resin, and polycyclic

aromatic hydrocarbons (PAH) compounds. These compounds are present in appreciable amounts and can be

used as signatures for source apportionment if special

precautions are taken during sampling to minimize

losses (Standley and Simoneit 1987). Inclusion of

these aerosol and VOC components in the speciation
50 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

analysis appears worthwhile but would increase monitoring and sample analysis costs.

Source Apportionment Methods

Apportionment of particulate matter mass to the

respective contributing sources is done through both

mechanistic models (dispersion models) and receptororiented techniques that are based on the characteristics of the particles collected at the receptor. The best

approach is through the use of both techniques, applied independently, to develop a “weight of evidence”

assessment of source contributions of smoke from fire.

A third approach is through the use of visual and

photographic systems that can document visibility

conditions over time or track a plume from its source

to the point of impact within a Class I area.

Figure 7-2—IMPROVE monitoring network in 1999 (http://vista.cira.colostate.edu/improve/Overview/IMPROVEProgram.htm).

Receptor-Oriented Approaches

Receptor-oriented approaches range from simple

signature applications to complex data analysis techniques that are based on the spatial, temporal, and

chemical constituents (“fingerprint”) of various sources.

Simple signature applications for smoke from fire

are based on chemically distinct emissions from fire.

For example, methyl chloride (CH3Cl) is a gas emitted

during wood combustion that has been used in this

manner to identify impacts of both residential

woodstove smoke and smoke from prescribed fires

(Khalil and others 1983).

Speciated Rollback Model —The speciated rollback model (NRC 1993) is a simple hybrid model that

uses aerosol data collected at the receptor with emission inventories to estimate source impacts. It is a
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 51

The limitations of the speciated rollback model are

several:

• Deviations from the assumption of spatially

homogeneous emissions are likely to occur

when air quality is most critical at a single

receptor where a single emission source can

have an inordinate impact.

• Secondary particle formation is assumed to be

linear to changes in precursor emissions.

• Meteorological conditions do not change from

year to year.

• Emission inventory errors have a direct, proportional effect on the model estimates.

The model can be applied to any temporal concentration such as annual average, worst 20th percentile, or

worst daily average scenarios in any region that meets

the constraint on the spatial distribution of emission

changes. It is straightforward, necessary input data

are available, and the model assumptions are easily

understood. It makes use of chemical speciation data

collected from the IMPROVE network but cannot

apportion contributions made from source classes not

included in the inventory.

Chemical Mass Balance Model—The chemical

mass balance model, CMB7 (Watson 1997; Watson

and others 1990), infers source contributions based on

speciated aerosol samples collected at a monitoring

site. Chemical elements and compounds in ambient

aerosol are “matched” to speciated source emission

profiles “fingerprints” by using least-squares, linear

regression techniques to apportion the aerosol mass.

CMB7 has been widely used within the regulatory

community to identify and quantify the sources of

particles emitted directly to the atmosphere. The model

is based on the relationship between characteristics of

the airborne particle (ci), the summation of the product

of the ambient mass concentration contributed by all

sources (Sj), and the fraction of the characteristic

component in the source’s fingerprint (fij).

ci = ∑jSjfij (2)

Given detailed information about the chemical speciation of the ambient aerosol and similar information

about all of the emission sources impacting the receptor, the CMB7 model can apportion the aerosol mass

among the sources if certain assumptions are met.

To minimize error, there must be more aerosol

components than sources to be included in the leastsquares linear regression fit. If there are more components measured than sources, then the comparison of

model-estimated concentrations of these additional

components provides a valuable internal check on

model consistency.

spatially averaged model that disaggregates major

particle components into chemically distinct groups

that are contributed by different types of sources. A

linear rollback model is based on the assumption that

ambient concentrations (C) above background (Cb) are

directly proportional to total emissions in the region of

interest (E):

C – Cb = kE (1)

The proportionality constant, k, is determined over

a historical time period when both concentrations C

and Cb as well as regional emissions E are known.

Once k is determined, new concentration estimates

can be derived for other emission levels of interest

assuming that meteorological conditions are constant

over the same averaging time. Because the anthropogenic components in the particle mass consist almost

entirely of sulfates, nitrates, organic carbon, elemental carbon, and crustal material, a maximum contribution from fire can be made based on the assumption

that all of the organic carbon or elemental carbon is

from primary fire emissions. Various complexities can

be added to this model; components can be disaggregated by particle-size fraction (coarse versus fine particles) as well as by chemical composition. Additional

distinctions can be made between primary and secondary particles, and nonlinear transformation processes can be approximated to account for atmospheric

reactions.

Simple proportional speciated rollback models require data on the chemical composition of airborne

particles, knowledge or assumptions regarding secondary particle components, an emission inventory

for the important source categories for each particle

component and each gaseous precursor, and knowledge or assumptions regarding background concentrations for each component of the aerosol and each

gaseous precursor.

The speciated rollback model was applied by the

NRC Committee on Haze in National Parks and Wilderness Areas to apportion regional haze in the three

large regions of the country (East, Southwest, and

Pacific Northwest) by including extinction coefficients

to the estimated mass concentrations (NRC 1993). The

percentage of anthropogenic light extinction apportioned to forest management burning was estimated

at 11 percent in the Northwestern United States on an

annual basis assuming that about one-third of the

measured organic carbon is of natural origin. The 1985

National Acid Precipitation Assessment Program

(NAPAP) inventory was used in this analysis, which

also assumed that the elemental carbon and organic

carbon fractions of the PM2.5 emissions for forest

management burning were 6 percent and 60 percent,

respectively.
52 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

The chemical components in the source “fingerprint” must be conserved and not altered during atmospheric transport — a rather large limitation.

Model resolution is typically limited to five or six

source types, and separation of two sources with similar emission profiles (for example, prescribed burning

and residential woodstove smoke) is difficult if both

sources are active at the same time.

Systematic error analysis procedures have been

developed for the CMB7 model, and the results have

been published in model validation studies (NRC

1993). However, the model cannot apportion secondary aerosols (sulfate and nitrate); it is limited in its

ability to apportion all of the mass to specific sources.

The ability of the model to apportion smoke from fire

depends on several factors:

• The presence or absence of smoke from other

forms of vegetative burning (woodstoves, agricultural burning, open burning, and others).

• The magnitude of the smoke impact at the

receptor (for example, well-dispersed smoke

that contributes small amounts of aerosol mass

is more difficult to distinguish).

• The uncertainty in both the ambient aerosol

and the source “fingerprint” components that

the model most heavily weights in the regression analysis, typically organic carbon, potassium, and elemental carbon. The greater the

uncertainty of these measurements, the less

“fitting pressure” they have in influencing the

regression solution.

• Inclusion of multiple aerosol components that

are as nearly unique to smoke from fires (endemic signatures) as possible. These include

organic compounds such as retene and

levoglucosan, as well as gaseous signature

such as carbon monoxide and methyl chloride.

The more the source profile distinguishes prescribed or wildland fire smoke from other

sources, the more accurate the source apportionment is likely to be.

Factor Analysis and Multiple Linear

Regression

When many ambient samples are available, linear

regression and factor analysis techniques can be applied to the dataset to obtain empirical insights into

the origin of the particles. Factor analysis is based on

the assumption that chemical components of the aerosol that covary are emitted from a common source.

Cluster patterns can then be matched to the source

profiles of known sources to identify the degree of

covariance associated with a specific source category.

Source profiles can be recovered from the ambient

data by using two special forms of factor analysis

(VARIMAX rotation) or, when the profiles are approximately known, target transformation factor analysis

(Hopke 1985). Factor analysis can therefore serve to

refine the source profile information used in chemical

mass balance analysis. In the context of wildfire smoke

apportionment, investigators have historically looked

for a high degree of covariance between organic carbon, elemental carbon, and potassium (total, water

soluble, and/or nonsoil potassium) as the cluster components that signal particles emitted from vegetative

burning of all kinds. Unfortunately, these components

of the aerosol are not necessarily unique to smoke from

vegetative burning.

Linear regression analysis is a well-established statistical procedure for estimating unknown coefficients

in linear relationships where a large dataset of observations of both the dependent and independent variables are present. In the terminology of regression

analysis, c in equation (2) is the variable, Sj is the

independent variable, and fj the regression coefficients. In practice, the independent variable is taken

to be proportional to source strength rather than the

source strength themselves. Multiple linear regression has been widely used to apportion total particle

mass, the most common approach being use of signature concentrations taken directly as the independent

variable, fj. Significantly, gaseous pollutant data can

be included in the regression to increase the model’s

ability to resolve sources. Although carbon monoxide

would greatly enhance the success of the model as it is

emitted by wildfires in large quantities and is stable in

the atmosphere, carbon monoxide is not routinely

included in nonurban monitoring programs.

Regression analysis has been used successfully to

apportion the total carbon portion of the aerosol mass

between wood smoke, vehicle exhaust, and other

sources by using nonsoil potassium . The regressionderived estimates were then validated by 14C isotope

analysis, which is a direct indicator of “contemporary”

versus fossil fuel carbon sources. The 14C measurements nicely confirmed the source apportionment results by regression analysis (r=0.88) (NRC 1993).

Summary

Receptor-oriented methods of particle mass source

apportionment have proven successful in a large number of urban studies worldwide. A number of these

studies have attempted to apportion wildfire smoke on

the basis of a set of aerosol and source emission trace

elements and compounds. The experimental design of

these studies has limited the ability of receptor models

to resolve wildfire smoke from other sources. With
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 53

improvements in speciation of the organic carbon

component of the aerosol, and inclusion of carbon

monoxide, methyl chloride, and other endemic signatures, the ability of these techniques to resolve sources

and minimize uncertainties will increase. Sensitivity

studies are needed to determine which additional

components beyond the standard array of trace elements, ions, and carbon fractions would be most beneficial to include in future monitoring programs.

Mechanistic Models _____________

As noted in chapter 6, multiple dispersion models

have been used to estimate air quality impacts of

single or multiple fires at local and regional scales.

Eulerian regional-scale models have been principally

used for source apportionment application both to

estimate contributions to particulate air quality and

regional haze. The suitability of such models for apportionment applications largely depends on the completeness and accuracy of the emission inventory inputs used by the model. Unfortunately, few field

validations are available.
54 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Notes

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________________________________________________________________

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 55

Chapter 8: Consequences of

Fire on Air Quality

The potential impacts of fire-induced degradation of

air quality on public health and welfare range from

occupational exposure of smoke on firefighters to

broader economic and social impacts and highway

safety.

Health Effects __________________

National Review of Health Effects

In 1996, the Environmental Protection Agency (EPA)

conducted an extensive review of the science relating

human health effects to particulate matter (PM), the

principal pollutant of concern from fires (EPA 1996).

The review found that (1) epidemiological studies

suggest a variety of health effects at concentrations

found in several U.S. cities and (2) ambient particles of

greatest concern to health were those smaller than 10

micrometers in diameter. Results of efforts to trace the

physiological and pathological responses of the body to

PM are unclear, and demonstration of possible mechanisms linking ambient PM to mortality and morbidity

are derived from hypotheses in animal and human

studies. It is known, however, that PM produces physiological and pathological effects by a variety of mechanisms, including:

• Increased airflow obstruction by PM-induced

narrowing of airways.

• Impaired clearance of lung pathways caused

by hypersecretion of mucus caused by PM

exposure.

• Lung responses to PM exposure including

hypoxia, broncho-constriction, apnea, impaired

diffusion and production of inflammatory

mediators.

• Changes in the epithelial lining of the alveolar

capillary membrane that increase the diffusion distances across the respiratory membrane, thereby reducing the effectiveness of

blood gas exchange.

• Inflammatory responses that cause increased

susceptibility to asthma, chronic obstructive

pulmonary disease (COPD) and infections.

Recent information also suggests that several subgroups within the population are more sensitive to PM

than others. Children are more likely to have decreased pulmonary function, while increased mortality has been reported in the elderly and in individuals

with cardiopulmonary disease. Asthmatics are especially susceptible to PM exposure. In addition, coarse

(2.5 to 10μm) particles from road dust or windblown

soil were found to have less toxicity than fine particles

(less than 2.5μm) that include acid aerosols, diesel
56 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

emissions, smoke from fires, and potentially carcinogenic PAH compounds.

Occupational Exposure to Wildland Fire

Smoke

Wildland firefighters and fire managers have long

been aware that smoke exposure occurs during their

work (Reinhardt and Ottmar 1997; Sharkey 1997).

Although the long-term health effects from occupational smoke exposure remain unknown, the evidence

to date suggests that brief, intense smoke exposures

can easily exceed short-term exposure limits in peak

exposure situations such as direct attack and holding

firelines downwind of an active wildfire or prescribed

burn. Shift-average exposure only occasionally exceeds

recommended instantaneous exposure limits set by the

American Conference of Governmental Industrial Hygienists (ACGIH), and rarely do they exceed Occupational Safety and Health Administration (OSHA) time

weighted average (TWA) limits (fig. 8-1) (Reinhardt

and Ottmar 2000; Reinhardt and others 2000). Overexposure increases to 10 percent of the time if the exposure limits are adjusted for unique aspects of the fire

management workplace; these aspects include hard

breathing, extended hours, and high elevations, all

factors which intensify the effects of many of the health

hazards of smoke (Betchley and others 1995; Materna

and others 1992; Reinhardt and Ottmar 2000; Reinhardt

and others 2000). It could be argued that few firefighters

spend a working lifetime in the fire profession, and thus

they should be exempt from occupational standards

that are set to protect workers over their careers. But

this argument is irrelevant for irritants and fast-acting

health effects such as eye and respiratory irritation,

headache, nausea, and angina. An exposure standard

specifically for wildland firefighters and appropriate

respiratory protection may need to be developed

(Reinhardt and Ottmar 2000).

In spite of the studies that have been done, major

data gaps remain:

• In the area of health hazards, not enough

evidence is available to defend the commonly

cited “inert” classification of total and respirable particulate in dust and smoke; there is

little knowledge of the occurrence of crystalline silica in dust at fires; and there is incomplete characterization of aldehydes and other

respiratory irritants present in smoke

(Reinhardt and Ottmar 1997, 2000).

• The differences in smoke exposure between

large and small wildland fires have not been

characterized in spite of the fact that one or

two crews extinguish the vast majority of

wildfires (Reinhardt and Ottmar 2000).

• The long-term health experience of wildland

firefighters is unknown, although anecdotal

reports and the biological plausibility of cumulative health effects indicate a potentially

greater incidence of disease and death than in

the general population of workers (Booze and

Reinhardt, in press; Sharkey 1997).

Although data gaps remain, enough information has

been gathered to chart a course to alleviate many of

the overexposures. Respiratory protection is available

for irritants such as aldehydes and particulate matter

but not for carbon monoxide. Respirators can be heavy,

hot, and impede the speed of work, but some new

models are light, simple and could be worn only when

needed (Beason and others 1996; Rothwell and Sharkey

1995). The entire costly process of medical evaluations, fitness testing, maintenance, and training must

be employed if respirators are to be used. But there are

immediate benefits to reducing respiratory irritant

exposure. Small electrochemical dosimeters can provide instant warnings about carbon monoxide levels in

a smoky situation, and fire crew members equipped

with respirators and carbon monoxide monitors have

all the protection necessary to stay and accomplish

objectives safely and withdraw when the carbon monoxide levels become the limiting factors (Reinhardt

and others 1999). In the future, a respirator for use

during wildland fires may be developed that offers

warning and protection against carbon monoxide as

well. Although some work has been done in this area,

we need more significant development. Smoke exposure is a hazard only a small portion of the time and is

Figure 8-1—Firefighters being monitored for smoke exposure.

Monitoring equipment seen includes a red backpack that collects gas samples from the breathing zone of the firefighters

and a white-colored particulate matter filter sampler attached to

the chest. (Photo by Roger Ottmar)
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 57

manageable because the situation where it occurs can

be predicted. A long-term program to manage smoke

exposure at wildland fires could include (1) hazard

awareness training, (2) implementation of practices to

reduce smoke exposure such as rotating crews and

providing clean air sites, (3) routine carbon monoxide

monitoring with electronic dosimeters, (4) improved

recordkeeping on accident reports to include separation of smoke related illness among fireline workers

and fire camp personnel, and (5) improved nutritional

and health habits. Fire management practices such as

crew rotation, awareness training, and carbon monoxide monitoring can mitigate the hazard and allow

firefighters to focus on the job of fire management,

lessening the distraction, discomfort, and health impacts of smoke exposure (Reinhardt and Ottmar 2000).

Research Issues

A number of wildland fire health effect research

issues flow from the EPA staff report (Clean Air

Scientific Advisory Committee1995) and occupational

health exposure studies.

Research into the health effects of particulate matter is largely based on epidemiological studies conducted over long periods in urban centers with high

hospital admittance or large air quality databases, or

both. Consequently, inadequate information is available that relates short-term, acute smoke exposure

(such as would be experienced by a visitor to a

National Park or to a community near a wildfire) to

human health effects. As a result, little or no specific

guidance is available to wildland fire managers, air

quality regulators, or public health officials who need

to responsibly judge the public health risks of exposure to extremely high smoke concentrations. This

gap in knowledge was clearly evident during the 1988

Yellowstone fires and later wildfire events when

quick decisions had to be made on how best to protect

public health in communities near major wildfires

(WESTAR 1995). The best available guidelines are

those published by EPA (1999) for assessing the risk

to health from air pollution (table 8-1). These guidelines may or may not reflect the specific hazards of

pollutants from fires, which will have a different

chemical composition.

Table 8-1—Pollutant-specific breakpoints for the air quality index (AQI) and accompanying health effects statements (adapted from

EPA 1999).

Category PM2.5 (24-hour) PM10 (24-hour)

Concentration Health effects Concentration Health effects

breakpoints statements breakpoints statement

μg/m3μg/m3

Good 0.0-15.4 None 0-54 None

Moderate 15.5-40.4 None 55-154 None

Unhealthy 40.5-65.4 Increasing likelihood of respiratory 155-254 Increasing likelihood of respiratory

for sensitive symptoms in sensitive individuals, symptoms and aggravation of lung

groups aggravation of heart or lung disease disease, such as asthma.

and premature mortality of persons

with cardiopulmonary disease and

the elderly.

Unhealthy 65.5-150.4 Increased aggravation of heart or lung 255-354 Increased respiratory symptoms and

disease and premature mortality in aggravation of lung disease, such

persons with cardiopulmonary disease as asthma; possible respiratory

and the elderly; increased respiratory effects in general population.

effects in the general population.

Very unhealthy 150.5-250.4 Significant aggravation of heart or lung 355-424 Significant increase in respiratory

disease and premature mortality in symptoms and aggravation of lung

persons with cardiopulmonary disease disease, such as asthma; increasing

and the elderly; significant increase in likelihood of respiratory effects in

respiratory effects in general population. general population.

Hazardous 250.5-500.4 Serious aggravation of heart or lung 425-604 Serious risk of respiratory symptoms

disease and premature mortality in and aggravation of lung disease,

persons with cardiopulmonary disease such as asthma; respiratory effects

and the elderly; serious risk of likely in the general population.

respiratory effects in general population.
58 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

The long-term health effects of smoke exposure to

wildland firefighters are unknown in spite of anecdotal evidence that indicates the possibility of a

greater incidence of cardiopulmonary disease and

death than in the general population. Although carbon monoxide monitoring and respiratory protection

can mitigate the hazard, personal protection equipment is still needed that allows firefighters to work

effectively without discomfort or distraction

(Reinhardt 2000).

Welfare Effects _________________

Air quality-related effects of smoke include the soiling of materials, public nuisance, and visibility loss.

Because these and other consequences of smoke have

come increasingly into conflict with the public’s interest in clean air, an understanding of these effects is

important to fire managers.

Soiling of Materials

The deposition of smoke particles on the surface of

buildings, automobiles, clothing, and other objects

reduces aesthetic appeal and damages a variety of

objects and building structures (Baedecker and others

1991). Studies of the effect of aerodynamic particle

size on soiling have concluded that coarse particles

(2.5 to 10μm) initially contribute more to soiling of

both horizontal and vertical surfaces than do fine

particles (less than 2.5μm), but that coarse particles

are more easily removed by rainfall (Haynie and

Lemmons 1990). Smoke from fires is largely within the

fine mode, although ash fallout in the near vicinity of

a fire is often also a concern. Smoke may also discolor

artificial surfaces such as building bricks or stucco,

requiring cleaning or repainting. Increasing the frequency of cleaning, washing, or repainting soiled surfaces becomes an economic burden and can reduce the

life usefulness of the soiled material (Maler and Wyzga

1976).

Soiling from smoke also changes the reflectance of

opaque materials and reduces light transmission

through windows and other transparent materials

(Beloin and Haynie 1975).

When fine smoke particles (less than 2.5μm) infiltrate indoor environments, soiling of fabrics, painted

interior walls, and works of art may occur. Curtains

may require more frequent washing because of soiling

or may deteriorate along folds in the fabric after being

weakened by particle exposure (Yocom and Upham

1977). As in the case of corrosion damage from acidified particles, these same particles accelerate damage

to painted surfaces (Cowling and Roberts 1954). Studies of the soiling of works of art at a museum in

southern California concluded that a significant fraction of the dark-colored fine mode elemental carbon

and soil dust originated from outdoor sources (Ligocki

and others 1993). Smoke from fires is one source of

elemental carbon.

Public Nuisance and Visibility Loss

Nuisance smoke is the amount of smoke in the

ambient air that interferes with a right or privilege

common to members of the public, including the use or

enjoyment of public or private resources (EPA 1990).

The abatement of nuisance smoke is one of the most

important objectives of successful smoke management (Shelby and Speaker 1990). Public complaints

about nuisance smoke are linked to loss of visibility,

odors, and ash fallout that soils buildings, cars, laundry, and other objects. Acrolein (and possibly formaldehyde) in smoke at distances of 1 mile from the

fireline are likely to cause eye and nose irritation,

exacerbating public nuisance conditions (Sandberg

and Dost 1990).

Perhaps the most significant nuisance effect of smoke

from fire is local visibility reduction in areas impacted

by the plume. While visibility loss within Class I areas

is subject to regulation under the Clean Air Act, smoke

plume-related visibility degradation in urban and

rural communities is not. Nuisance is usually regulated under State and local laws and is frequently

based on public complaint or, when highway safety is

compromised, the risk of litigation (Eshee 1995). The

courts have also ruled that the taking of private

property by interfering with its use and enjoyment

caused by smoke (and without just compensation) is in

violation of Federal Constitutional provisions under

the Fifth Amendment. The trespass of smoke may

diminish the value of the property, resulting in losses

to the owner (Iowa Supreme Court 1998).

Because the public links visibility loss with concerns

about the health implications of breathing smoke,

smoke management programs have been under increasing pressure to minimize emissions and reduce

smoke impacts to the greatest degree possible (Core

1989). Visibility reduction is used as a measure of

smoke intrusions in several smoke management plans.

The State of Oregon program operational guidance

defines a “moderately” intense intrusion as a reduction of from 4.6 to 11.4 miles from a background

visibility of more than 50 miles (Oregon Department of

Forestry 1992). The State of Washington smoke intrusion reporting system uses a “slightly visible,” “noticeable impact on visibility” or “excessive impact on

visibility“ to define light, medium, and heavy intrusions (Washington Department of Natural Resources

1993). The State of New Mexico program requires that

visibility impacts of smoke be considered in development of the unit’s burn prescription (New Mexico

Environmental Improvement Board 1995).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 59

Economic and Social

Consequences__________________

The economic consequences of smoke are principally

in the areas of soiling-related losses and costs related

to reduced visibility.

Soiling-Related Economic Losses

Economic costs associated with materials damage

and soiling caused by airborne particles include reduction in the useful life of the damaged materials and the

decreased utility of the object. Losses caused by the

need for more frequent maintenance and cleaning are

also significant. Amenity losses occur when the increased cleaning or repair of materials results in

inconvenience or delays, many of which are difficult to

quantify (Maler and Wyzga 1976).

Within the United States, however, the soiling of

buildings constitutes the largest category of surface

areas at risk to pollution damage (Lipfert and Daum

1992). Soiling on painted surfaces on residential buildings, resulting in a need to repaint exterior walls, has

caused damage approaching $1 billion per year (Haynie

and others 1990).

Willingness-to-pay estimates developed using the

contingent valuation method found that households

were willing to pay $2.70 per μg/m3 charge in particle

pollution to avoid soiling effects (McClelland and others 1991). No estimates are available for costs specifically associated with smoke from fires.

Visibility-Related Costs

The importance of clean, clear air within the wildlands and National Parks of this nation is hard to

overemphasize. People go to these special places to

enjoy scenery, the color of the landscapes, and clarity

of the vistas. At Grand Canyon, 82 percent of 638

respondents rated “clean, clear air” as very important

or extremely important to their recreational experience (Ross 1988). Three National Park Service (NPS)

studies determined that air quality conditions affect

the amount of time and money visitors are willing to

spend at NPS units (Brookshire and others 1976;

MacFarland and others 1983; Schulze and others

1983). These studies found estimated onsite use values for the prevention or elimination of plumes that

ranged from about $3 to $6 (1989 dollars) per day per

visitor party at the park. Based on these results, the

implied preservation value for preventing a visible

plume most days (the exact frequency was not specified) at the Grand Canyon was estimated at about $5.7

billion each year when applied to the total U.S. population (EPA 1996). Other investigators have suggested

that these estimates are overstated by a factor of 2 or

3 (Chestnut and Rowe 1990).

In the studies noted above, park visitors generally

responded that they would be willing to spend more

time and money if visibility conditions were better

and, conversely, less if visibility conditions were worse

(Ross 1988). The average amount of time visitors were

willing to spend traveling to a vista for every unit

change in visibility (.01 km–1 extinction coefficient)

was between 15 minutes and 4 hours. These results

provide evidence that changes in visual air quality can

be expected to affect visitor enjoyment and satisfaction with park visits.

Even given the limitations and uncertainties of

contingent valuation surveys, economic values related to visibility degradation are clearly likely to be

substantial.

Public Perception of Haze—Perceived visual air

quality (PVAQ) has been used as a measure of the

public’s acceptance of haze conditions (Middleton and

others 1983). Subjects were asked to judge the visual

air quality in several photos depicting vistas under

different haze conditions using a scale of 1 to 10, 1

being the worst and 10 being the best. These 1 to 10

scales reflect people’s perceptions and judgments concerning visibility conditions. By matching particulate

air quality conditions that occurred at the time of the

photographs, researchers have been able to develop a

relationship between PVAQ and particulate matter

concentrations (Middleton and others 1985). Even

small increases in particulate concentrations in the

atmosphere result in dramatic decreases in PVAQ.

Because of the light scattering efficiency of smoke, this

relationship is especially applicable to fire emissions.

Cultural Consequences of Visibility Loss—“National parks and wilderness areas are among our

nation’s greatest treasures. Ranging from inviting

coastal beaches and beautiful shorelines to colorful

deserts and dramatic canyons to towering mountains

and spectacular glaciers, these regions inspire us as

individuals and as a nation” (NRC 1993). With these

words, the National Research Council (NRC) noted

the importance of preserving the scenic vistas of the

nation. Congress, in recognition of the scenic values of

the nation, adopted the Clean Air Act Amendments of

1977, which established a national visibility protection program. The GCVTC was later established in the

1990 amendments to the act to address visibility

impairment issues relevant to the region surrounding

Grand Canyon National Park. Following 4 years of

study, the GCVTC concluded that smoke from wildland fires is likely to have the single greatest impact on

visibility in Class I areas of the Colorado Plateau

through the year 2040 (GCVTC 1996c). While difficult

to quantify, there is consensus that visibility loss

associated with smoke from wildland fire and other

sources has important cultural consequences on the

nation.
60 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Highway Safety _________________

Smoke can cause highway safety problems when it

impedes a driver’s ability to see the roadway (fig. 8-2)

and can result in loss of life and in property damage at

smoke levels that are far below NAAQS. This section

focuses on highway safety issues in the Southeastern

United States because this is where the foremost

forestry-related air quality problem has been in the

past. We also describe tools being developed to aid the

land manager in avoiding highway safety problems.

Although smoke at times can become a problem

anywhere in the country, it is in the Southern States,

from Virginia to Texas and from the Ohio River southward, where highway safety is most at risk from

prescribed fire smoke, principally because of the

amount of burning done in the South and the proximity of wildlands to population centers. Roughly 4

million acres of Southern forests are treated with

prescribed fire each year (after Wade and Lunsford

1988). This area is by far the largest acreage subjected

to prescribed fire in the country. Prescribed fire treatment intervals, especially in Southern pine (in an area

extending roughly from Virginia to Texas), is every 3

to 5 years. These forests are intermixed with homes,

small towns, and scattered villages within an enormous wildland/urban interface. During the daytime,

smoke becomes a problem when it drifts into these

areas of human habitation. At night, smoke can become entrapped near the ground and, in combination

with fog, creates visibility reductions that cause roadway accidents. The potential exists for frequent and

severe smoke intrusions onto the public roads and

highways from both prescribed and wildland fires.

Magnitude of the Problem

Smoke and smoke/fog obstructions of visibility on

Southeastern United States highways cause numerous accidents with loss of life and personal injuries

every year. Several attempts to compile records of

smoke-implicated highway accidents have been made.

For the 10 years from 1979 through 1988, Mobley

(1989) reported 28 fatalities, over 60 serious injuries,

numerous minor injuries, and millions of dollars in

lawsuits. During 2000, smoke from wildfires drifting

across Interstate 10 caused at least 10 fatalities, five

in Florida and five in Mississippi.

As the population growth in the South continues,

more people will likely be adversely impacted by

smoke on the highways. Unless methods are found to

adequately protect public safety on the highways,

there exists the prospect that increasingly restrictive

regulations will curtail the use of prescribed fire or

that fire as a management tool may be altogether

prohibited.

Figure 8-2—Smoke can cause highway safety problems

when it impedes a driver’s ability to safely see the roadway.

(Photo by Jim Brenner)

Measures to Improve Highway Safety

Several approaches are being taken to reduce the

uncertainty of predicting smoke movement over

roadways:

High-resolution weather prediction models promise

to provide increased accuracy in predictions of wind

speeds and directions and mixing heights at time and

spatial scales useful for land managers. The Florida

Division of Forestry (FDOF) is a leader in the use of

high resolution modeling for forestry applications in

the South (Brenner and others 2001). Because much

of Florida is located within 20 miles of a coastline,

accurate predictions of sea/land breezes and associated changes in temperature, wind direction, atmospheric stability, and mixing height are critical to the

success of the FDOF. High-resolution modeling consortia are also being established by the USDA Forest

Service to serve clients with interests as diverse as

fire weather, air quality, ecology, and meteorology.

These centers involve scientists in development of

new products and in technology transfer to bring the

products to consortia members.

Several smoke models are in operation or are being

developed to predict smoke movement over Southern

landscapes. VSMOKE (Lavdas 1996), a Gaussian

plume model that assumes level terrain and unchanging winds, predicts smoke movement and concentration during daytime. VSMOKE has been made part of

the FDOF fire and smoke prediction system. It is a

screening model that aids land managers in assessing
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 61

where smoke might impact sensitive targets as part of

planning for prescribed burns. PB-Piedmont

(Achtemeier 2001) is a wind and smoke model designed to simulate smoke movement near the ground

under entrapment conditions at night. The smoke

plume is simulated as an ensemble of particles that

are transported by local winds over complex terrain

characteristic of the shallow (30 to 50 m) interlocking

ridge/valley systems typical of the Piedmont of the

South. Two sister models are planned — one that will

simulate near-ground smoke movement near coastal

areas influenced by sea/land circulations, and the

other for the Appalachian Mountains.

Climate Change _________________

Globally, fires are a significant contributor of carbon

dioxide and other greenhouse gases in the atmosphere.

Fires are also an important mechanism in the redistribution of ecosystems in response to climate stress,

which in turn affects the atmosphere-biosphere carbon balance. Currently, there is no policy mandate,

nor widely accepted methodology for managing fires,

for the conservation of terrestrial carbon pools or

mitigation of greenhouse gas emissions. However, we

may expect carbon accounting and perhaps conservation to become a part of fire and air resource management if and when global agreements are made to

address biomass burning and resultant greenhouse

gas emissions.
62 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Notes

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 63

Chapter 9:

Recommendations for Future

Research and Development

Managing smoke and air quality impacts from fires

requires an increasing base of knowledge obtained

through research and the development of information

systems. Fire and air resource managers have had the

responsibility since the 1960s to mitigate direct intrusions of smoke into areas where it presents a health or

safety hazard, or where it is simply objectionable to an

affected population. In more recent years, that responsibility has broadened because of an increase in the

use of fire, more people in the wildland/urban interface, tightening of regulatory standards, and decreasing public tolerance for air pollution. More States

require smoke management plans, and the plans are

increasingly complex due to increased coverage and

greater requirements for notification, modeling, monitoring, and recordkeeping.

Established Research

Framework _____________________

There is ample strategic analysis and workshop

output to guide research. The most comprehensive

and up-to-date recommendations for research and

development are found in National Strategic Plan:

Modeling and Data Systems for Wildland Fire and Air

Quality (Sandberg and others 1999). Workshop sessions, internal discussion, and review comments were

compiled into more than 200 proposals from which 46

priority projects were selected that support the nine

summary recommendations outlined here.

Recommendation 1: Fuels and fire characteristics—An ability to estimate emissions from all types

of fires over the wide variation in fuels in the contiguous United States and Alaska is needed. Expanded

models and fuel characteristics data are needed to fill

this gap.

Recommendation 2: Emissions modeling systems—Current models to estimate emissions are inadequate in coverage and incomplete in scope. Emissions production models need to be expanded to include

all fire and fuel types as well as linked to fire behavior

and air quality models in a geographically resolved

data system.

Recommendation 3: Transport, dispersion, and

secondary pollutant formation—Air quality and

land management planners lack spatially explicit planning and real-time systems for assessing air quality

impacts. A geographic information system (GIS) based
64 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

system linked to emissions production, meteorological, and dispersion models is needed.

Recommendation 4: Air quality impact assessment—Better wildland and prescribed fire information is needed to compile emissions inventories, for

regional haze analysis and for determination of compliance with National Ambient Air Quality Standards

(NAAQS).

Recommendation 5: Emissions tradeoffs and

determination of “natural” visibility background

assessments—No policy-driven or scientific definition of “natural” background visibility exists for regional haze assessments. The tradeoffs between wildfire and prescribed fire emissions are also not known.

To address these issues, the policy community needs

to decide what types of fires contribute to natural

impairment after which a scientific assessment could

be done and tradeoffs evaluated.

Recommendation 6: Impact and risk assessment of emissions from fire—A comprehensive

assessment of smoke exposure of prescribed and wildland firefighters and the public at current levels of fire

activity should be done to provide a baseline for future

risk assessments. Exposures should be periodically

reassessed to evaluate increased risks from future

increases in fire emissions.

Recommendation 7: Monitoring guidelines and

protocols—Guidelines are needed on how best to

monitor source strength, air quality, visibility, and

nuisance impacts from fires to support consistent and

quantitative evaluation of air impacts.

Recommendation 8: National fire and air quality information database—A readily accessible

source of information on past, current, and predicted

future fire activity levels, emissions production, and

air quality impacts from fires does not exist. Such a

database is needed to analyze past experiences and

replicate successes.

Recommendation 9: Public information and

protection—A centralized system is needed to provide information to the public on air quality impacts

from fires. Also needed are general criteria for how

land managers, air regulators, and public health officials should respond to adverse smoke impacts and

emergency notifications of the public to health hazards associated with smoke from fire.

The authors of this plan hoped that these recommendations would be used in future joint agency

efforts to advance the fire sciences, minimize duplication of effort, and share information among agencies

and the public.

The technically advanced smoke estimation tools, or

TASET, project (Fox and Riebau 2000) was funded by

the Joint Fire Sciences Program (JFSP) to develop a

structured analysis of smoke management and recommend specific developments for advancing the state of

science. The report confirmed and refined the recommendations of Sandberg and others (1999) above, and

developed 10 recommendations for research activities:

• Fire community participation in regional air

quality modeling consortia.

• Conduct a national smoke and visibility conference and reference guide.

• Develop a national smoke emissions data structure or database system.

• Apply remote sensing for fuels and fire area

emissions inventories.

• Develop a fire gaming system to quantify emissions and impacts from alternative fire management practices.

• Improve the CalMet/CalPuff smoke management model.

• Upgrade a nationalized screening model/

simple approach smoke estimation model

(SASEM).

• Provide onsite fire emissions verification.

• Utilize back-trajectory modeling and filter

analysis for fire smoke contributions for

nonattainment areas.

• Develop a method to identify the specific

sources of organic carbon fine particulate

material.

Research priorities established in the Effects of Fire

Air (Sandberg and others 1979) are unfortunately still

valid today, although some progress has been made in

every category. We list these here, slightly reworded

from the original for brevity and to conform to modern

nomenclature:

1. Provide quantitative smoke management systems.

a. Develop information systems necessary to

support smoke management decisions.

b. Provide a smoke management reporting system for emission rates based on the prediction

of fuel consumption, fire behavior, heat release rates, and source control measures.

c. Provide the data network and modeling scheme

to calculate the change in pollution concentrations and character between the source and

potential receptors.

d. Adapt plume rise models necessary to predict

the vertical distribution of emissions from

fires.

2. Characterize the chemistry and physics of

emissions.

a. Relate emissions and heat release rates to

fuelbed characteristics and fire behavior.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 65

b. Advance our knowledge of hazardous and reactive compounds in smoke.

c. Develop field methods to monitor emission

rates and smoke chemistry from operational

fires.

d. Investigate the potential for secondary reactions of emissions downstream from their

source.

3. Model atmospheric transport, diffusion, transformation, and removal mechanisms.

a. Continue development of winds and dispersion models for boundary layer flow and mesoscale transport of smoke over mountainous

terrain.

b. Investigate the mechanisms of removal; for

example, canopy interactions, fallout, and local deposition.

c. Interact with the wider scientific community

to establish the effect of reactive pollutants on

the biosphere.

d. Evaluate the potential contribution of wildland fires to climate change.

4. Identify receptor responses to wildland smoke.

a. Identify and quantify the visibility needs of

wildland users, and recommend standards for

particulate and sulfate pollution from all

sources affecting Class I visibility areas.

b. Evaluate the potential impact of wildland

smoke on human health.

c. Investigate the role of wildland ecosystems as a

sink and receptor for atmospheric contaminants.

5. Investigate tradeoffs made in the substitution of

alternatives to fire use.

a. Develop simulation models to evaluate interactions of land use policy with air resource

management. Incorporate air resource management and fuels management needs into

the land use planning process.

b. Evaluate the effect on wildland fire occurrence

and air pollution from changes in the amount

of prescribed fire activity.

c. Describe the resource and economic tradeoff of

wildland fire occurrence resulting from a

change in prescribed fire activity.

d. Investigate the effect of changes in fire use on

nutrient cycling, successional response, and

ecosystem stability.

Emerging Research Needs________

Several new responsibilities create the need for

additional information systems that require new research and development, including:

• Planning rules that require the consideration

of cumulative pollution and visibility impacts

of fuel management programs.

• Wildland fire situation analysis requirements

that smoke impacts from wildland be anticipated and communicated to the public.

• Increased requirements for emission reduction.

• Policies that require hourly and daily tracking

of emissions and the management of smoke

from all fires.

• Increased management of wildland fires for

resource benefits.

• Increased use of long-duration landscape-scale

fires.

• Regulatory concern over secondary pollutants,

especially ozone formation and the reentrainment of mercury.

• Questions about the role of fire and global

biomass emission on atmospheric carbon and

global warming.

• Increased attention to firefighter health effects from exposure to smoke.

Each of these factors requires information systems

for planning, operations, and monitoring the effects of

fire on air. Using the framework illustrated in figures

1-1 and 1-2 (in chapter 1) and the background of

previous chapters, some emerging research needs are

outlined below.

Emissions Source Strength and

Emissions Inventory

Level of burn activity: Accurately predict, determine, and record the area burned and time of

burning for all types of prescribed and wildland

fire—Area burned is still the parameter that imparts

the greatest error into predictions of source strength

and emission inventory. Needed are: a balanced program of new planning models that project area burned

and fire residence times; remote-sensing technologies

that track fire sizes at hourly intervals; ground based

sampling, reporting, and communication systems; and

analysis tools. Planning models include those that

project fire use and predict wildland fire activity from

1 to 50 years in the future must be included, as well as

accurate predictions made a day in advance.

Biomass: Accurately predict, determine, and

record the mass, combustion stage, and residence time of fuels burned in all types of fires—

Inadequate representation of fuelbed characteristics

and the ability to infer fuelbed characteristics and

flammability conditions from remote sensing or ecosystem physiognomy is the second greatest remaining

source of error. Models of the combustion process,
66 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

while improving, are still inadequate to predict or

characterize emission rates and durations. New classification systems, inference models, inventory and

sensing processes, and process models are needed.

Heat release and emissions: Predict and measure physical and chemical characteristics of

emissions from all types of fires—Among the greatest advances since about 1980 has been the nearly

complete characterization of primary and criteria pollutants from a wide range of fire environments. New

models also greatly improve the prediction and characterization of emissions source strength. Emission

factors for criteria pollutants are adequate. There is

substantial remaining uncertainly in the measurement and prediction of precursors to ozone and other

secondary chemical formations, secondary entrainment of mercury, production and stimulation of nitrogen compounds, air toxics, and greenhouse gases.

Continuing research on these trace constituents are

needed. In addition, we lack models that characterize

the complex spatial and temporal distribution of heat

release from fires.

Emissions inventory methods: Integrate measurements and reporting from remote sensing,

airborne platforms, simulation models, and surface observations into a fine-scale spatial and

temporal emission inventory—Emission inventories are a fundamental tool that air resource managers

use to calculate the relative importance of air pollution

sources and to design control strategies. Hourly, pointspecific emission estimates as well as daily, monthly,

and yearly summaries are necessary to compare fire

with other sources or as inputs to dispersion models.

Fire managers currently lack a system of observations

and reporting mechanisms required for planning, tracking, and monitoring emissions.

Ambient Air Quality Impacts

Background air quality: Improve the accessibility of girded detail about background air

quality and meteorological conditions—Fire

emissions are inserted into an already complex atmosphere, and current ability to predict pollutant interactions, transformations, and combined effects are

limited by the availability of hourly fine-scale atmospheric profiling.

Plume rise and transport: Improve the prediction, detection, and tracking of plumes from

all types and stages of fires—Fire plumes are

complex; often splitting into lofted and unlofted portions; plumes that split in two directions at different

altitudes, and plumes that change rapidly over time.

Plumes are transported long distances, often over

complex terrain, and the accuracy and availability of

models to predict transport are inadequate. Methods

to track plume trajectories and measure pollutant

concentrations in near real time using remote sensing

are emerging but not yet available.

Dispersion, dilution, and pollutant transformation: Improve the ability on all scales to predict, model, and detect changes in the properties and concentration of pollutants over time

and space—Data and models are needed to initiate

and predict local, regional, national, and global air

quality impacts from individual fires to the cumulative effects of tens of thousands of fires.

Atmospheric carbon balance and climatic

change: Develop consistent technologies to assess the contribution of fires to greenhouse gases

in the atmosphere and the effect of fire and

ecosystem management practices—For a source

of greenhouse gas emissions as large as wildland and

prescribed fires, there is a regrettable lack of consensus on the magnitude or even the methods for assessment and accountability. This emerging issue requires much of the same research on source

characteristics and air quality as do the health, safety,

and visibility issues, but also requires integration

with the global science and policy communities.

Effects on Receptors

Visibility and other welfare effects: Predict,

measure, and interpret the impact of natural

and anthropogenic fire sources on visibility,

economic, and other welfare effects—The impact

of smoke exposure from fires on human health standards is minor relative to the nuisance it creates and

the impacts on visibility. New science is required to

monitor and predict effects on visibility, and to apportion visibility impacts to specific sources and classes of

sources.

Health and safety risk assessment: Develop

knowledge and systems to assess the risk of

individual and collective fires to personal and

community health and safety—This broad topic

has received limited attention in recent years, mostly

in the prediction of visibility impacts on highway

safety and in the assessment of individual firefighter

exposure to hazardous air pollutants. But all aspects

of risk management, including hazard identification,

exposure assessment, dose-response, risk assessment,

and mitigation measures are lacking.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 67

Conclusion_____________________

Knowledge and information requirements for managing fire effects on air quality continue to increase.

Policy advancements require the understanding, modeling, prediction, monitoring, and tracking of fires and

their effect on air at greater detail and in greater

volume than ever before. Research and development

has progressed logically over the past 25 years due to

strategic planning and prioritization that has included

the needs of the managers of ecosystems and of air

quality. Analytical and information transfer capacity

has increased dramatically in the past decade, so

information is more readily accessible to those who

need it. Thanks largely to the National Fire Plan, the

Joint Fire Science Program, the Western Regional Air

Partnership, and EPA’s implementation of the Regional Haze Rule, there is currently more active research and development the effects of fire on air than

ever before.
68 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

Notes

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 69

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A

Africa. See World: Africa: tropical

air pollutants 2, 3, 9, 10, 14, 27

carbon dioxide (CO2

) 24, 27, 61

carbon monoxide

(CO) 9, 10, 11, 20, 31, 42, 49, 52, 53, 56, 57, 58

criteria 10, 11, 29, 32, 36, 49, 66

hazardous air pollutants

(HAP) 5, 9, 16, 29, 32, 45, 67

hydrocarbons 9, 10, 32

particulate matter (PM) 45

PM10 11, 13, 16, 20, 24, 25, 48, 49

PM2.5 4, 11, 13, 24, 41, 47, 48, 49, 51

primary 9

secondary 9

air pollution 1, 2, 4, 5, 9, 10, 11, 13, 15, 27, 45, 46, 48,

57, 63, 65, 66

Alabama. See United States of America: Alabama

Alaska. See United States of America: Alaska

ALOFT-FT. See models: ALOFT-FT

ambient air 2, 9, 10, 19, 20, 24, 35, 36, 41, 49, 58, 66

Appalachian Mountains. See United States of America:

Appalachian Mountains

Arizona. See United States of America: Arizona

Arkansas. See United States of America: Arkansas

Asia. See World: Asia: tropical

B

BEHAVE. See models: BEHAVE

BURNUP. See models: BURNUP

C

Cal/PFIRS. See models: Cal/PFIRS

California. See United States of America: California

Calpuff. See models: Calpuff

Canada. See World: Canada

carbon dioxide. See air pollutants

carbon monixide. See air pollutants

Central States Regional Air Partnership. See regional

planning organizations

Clean Air Act. See laws and regulations

CMAQ. See models

Colorado. See United States of America: Colorado

combustion stages 27, 30, 31, 42, 49, 65

flaming 29, 30, 31, 32, 36, 37

residual 29, 30, 31, 32, 37

smoldering 29, 30, 31, 32, 36, 37

Consume. See models

control measures 16, 64

E

emission factor 27, 29, 32, 43, 45, 46, 66

emission inventory 2, 45, 46, 47, 48, 64, 65

emission production model. See also models

emission(s)

anthropogenic 1, 9, 15, 49, 51, 66

chemistry 36

estimating 27, 29

greenhouse gas 61

natural 1, 5, 9, 15, 64, 66

prescribed fire 5, 7, 13, 16, 64

rates 29, 32, 38, 40. See also source strength

redistribution 17

reduction 4, 6, 16, 17, 45, 46, 48, 65

wildland fire 5, 7

EPA 4, 5. See U.S. Environmental Protection Agency

EPM. See models: Emission production model (EPM)

F

FARSITE. See models

FASTRACS. See models

FCAMMS. See Fire Consortia for Advanced Modeling of

Meteorology

FCC. See fuel: fuel characteristic classification system

(FCC)

Federal Wildland Fire Policy 1, 6

FEJF. See Fire Emissions Joint Forum (FEJF)

fire behavior 15, 27, 29, 36, 63, 64, 65

Fire Consortia for Advanced Modeling of Meteorology

15. See regional planning organizations

Fire Emissions Joint Forum (FEJF) 26

FIRETEC. See models

Florida. See United States of America: Florida

FOFEM. See models

fuel

arrangement 46

characteristics 27, 28, 31, 32, 36, 63, 65

consumption 7, 17, 27, 28, 30, 31, 32, 36, 46,

47, 64

fuel characteristic classification system (FCC) 28

loading 16, 28, 31, 37, 46

moisture 27, 46

G

GCVTC. See Grand Canyon Visibility Transport Commission

(GCVTC)

general conformity. See laws and regulations

Georgia. See United States of America: Georgia

global impacts

biomass burning and emissions 19, 36, 42, 43, 61

global change 36

greenhouse gases 24, 66

Grand Canyon. See United States of America: Grand Canyon

Grand Canyon Visibility Transport Commission

(GCVTC) 24, 46, 47, 59

Index
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 77

H

HAP. See air pollutants: hazardous air pollutants (HAP)

health 2, 4, 6, 11, 16, 20, 24, 35, 45, 55, 56, 57, 63, 66

community 7

effects 1, 11, 45, 55, 56, 57, 65

firefighter 65

human 6, 9, 11, 16

public 6, 7, 20

risks 5, 45, 57, 64

HIGRAD. See models

hydrocarbons. See air pollutants

Hysplit. See models

I

Idaho. See United States of America: Idaho

Illinois. See United States of America: Illinois

IMPROVE 48, 49, 51

Iowa. See United States of America: Iowa

J

Joint Fire Science Program (JFSP) 2, 6, 64, 67

L

laws and regulations

Clean Air Act 1, 4, 6, 9, 10, 11, 12, 13, 15, 16, 49, 58, 59

roles and responsibilities 10

general conformity 10, 11

National Environmental Policy Act (NEPA) 4

liability. See safety

Louisiana. See United States of America: Louisiana

M

Massachussetts. See United States of America: Massachusetts

meteorology 4, 10, 60, 64

Michigan. See United States of America: Michigan

Midwest Regional Planning Organization. See regional

planning organizations

Mississippi. See United States of America: Mississippi

model types

chemical mass balance (CMB) 51

dispersion 32, 35, 36, 37, 38, 40, 50, 64, 65, 66

grid 32, 37, 39, 40

particle 39

plume 37, 38, 39, 40, 60

puff 37, 39, 40

scavenging 38

transport 35, 37

models

ALOFT-FT 39

BEHAVE 29

BURNUP 29, 33, 36, 37

Cal/PFIRS 48

CALMET 38, 64

Calpuff 36, 39, 40, 64

CMAQ 32

Consume 31, 32

Emission production model (EPM) 29, 32, 36, 37

FARSITE 29, 33, 36

FASTRACS 48

FIRETEC 29

FOFEM 31, 32

HIGRAD 29

Hysplit 39, 40

MM5 38

Models-3/CMAQ 32, 36, 38, 40, 41

NFSpuff 39, 40

NUATMOS 38

PB-Piedmont 39, 61

RAMs 38

REMSAD 40

SASEM 36, 37, 39, 40, 64

TSARS+ 38

VSMOKE 36, 37, 39, 60

Models-3/CMAQ. See models

monitoring 3, 4, 5, 11, 15, 17, 25, 26, 45, 48, 49, 50,

51, 52, 53, 57, 63, 64, 66

Montana. See United States of America

N

NAAQS 4, 5. See national ambient air quality standards

(NAAQS)

national ambient air quality standards

(NAAQS) 4, 5, 10, 11, 16, 17, 19, 24, 25, 48, 49, 60, 64

National Fire Plan 7, 67

National Interagency Fire Center (NIFC) 6, 24

National Wildfire Coordinating Group (NWCG) 3, 4

NEAP. See smoke management planning: natural events

action plan (NEAP)

NEPA. See laws and regulations: National Environmental

Policy Act (NEPA)

Nevada. See United States of America: Nevada

New Mexico. See United States of America: New Mexico

New York. See United States of America: New York

NFSpuff. See models

NIFC. See National Interagency Fire Center (NIFC)

nonattainment 10, 11, 16, 24, 25, 64

North Carolina. See United States of America: North Carolina

NWCG. See National Wildfire Coordinating Group (NWCG)

O

Oregon. See United States of America: Oregon

OTC. See regional planning organizations

ozone 5, 10, 11, 17, 39, 40, 41, 42, 43, 45, 49, 65, 66

Ozone Transport Commission. See regional planning

organizations

P

Pacific Northwest. See United States of America: Pacific

Northwest

particulate matter 4, 5, 11, 20, 24, 32, 48, 49, 50, 55,

56, 59, 64

particulates 9, 10

PB-Piedmont. See models

PFIRS. See smoke management programs: Prescribed Fire

Incident Reporting System

photo series 28

Piedmont. See United States of America: Piedmont

plume 17, 23, 24, 27, 29, 36, 37, 38, 39, 40, 41, 42, 43,

50, 58, 59, 61
78 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002

chemistry 38, 39, 42

plume rise 35, 36, 37, 39, 40, 66

prevention of significant deterioration (PSD) 10, 12, 13

R

RAMs. See models

regional haze 4, 5, 10, 13, 14, 15, 17, 24, 26, 36, 39,

40, 41, 43, 45, 46, 48, 51, 53, 64, 67

regional planning organizations 14, 40

Central States Regional Air Partnership 14

Midwest Regional Planning Organizationrship 14

Ozone Transport Commission 41

Visibility Improvement State and Tribal Associatio 14

REMSAD. See models

research questions 1, 2, 4, 7, 10, 17, 31, 37, 40, 42,

43, 47, 48, 57, 59, 63, 64, 65, 66, 67

Rocky Mountain. See United States of America: Rocky

Mountain

Russia. See World: Russia

S

safety 1, 4, 6, 16, 63, 66

firefighter 7

highway 23, 58, 60, 66

liability 5, 25

public 6, 25, 60

roadway 23, 60

SASEM. See models

scavenging 36, 37, 38, 40

SIP. See smoke management programs: State

implementation plan (SIP)

smoke

dispersion 4, 15, 17, 26, 36

prescribed fire 25, 52, 60

reduction. See emission(s): reduction

transport 6, 14, 25, 26

wildland fire 49, 52, 56

smoke management guidance

smoke management guide for prescribed and wildland

fire 2, 3, 4, 5, 17

southern smoke management guidebook 2, 6

smoke management guide for prescribed and wildland

fire. see smoke management guidance

smoke management planning 16

enhanced smoke management plan 26

natural events action plan (NEAP) 16, 24

smoke management

programs 4, 5, 15, 16, 17, 19, 24, 25, 58

Prescribed Fire Incident Reporting System 26

State implementation plan

(SIP) 5, 10, 11, 16, 17, 40, 46

Tribal implementation plan (TIP) 10, 40

source strength 2, 32, 33, 36, 39, 40, 52, 64, 65, 66

Southern Smoke Management Guidebook. See smoke

management guidance

South America. See World: South America

South Carolina. See United States of America: South

Carolina

T

Tennessee. See United States of America: Tennessee

Texas. See United States of America: Texas

TIP. See smoke management programs: Tribal implementation plan (TIP)

U

U.S. Environmental Protection Agency 4, 5, 7, 10, 12,

14, 16, 17, 19, 20, 24, 25, 39, 41, 47, 48, 55, 57, 58, 59

United States of America

Alabama 25

Alaska 19, 25, 40, 42, 63

Appalachian Mountains 61

Arizona 24, 25, 39, 46

Arkansas 25

California 15, 19, 20, 24, 25, 26, 46, 48, 58

Central Valley 20

San Joaquin Valley 26

southern 58

Colorado 25, 39, 46

Colorado Plateau 59

Eastern Seaboard 20

Eastern U.S. 51

Florida 19, 20, 25, 46, 60

Georgia 24, 25

Grand Canyon 59

Idaho 20, 24, 46

Salmon 20

Illinois 25

Intermountain West 19

Iowa 58

Louisiana 25

Massachusetts 25

Michigan 46

Midwestern States 41

Mississippi 25, 60

Montana 20, 24, 46

Montana/Idaho 15, 25

Nevada 20, 25, 26, 46

Reno 20

New Mexico 20, 25, 39, 46, 58

New York 25

North Carolina 25

Northeastern 15

Northwestern U.S. 51

Ohio 60

Ohio River 60

Oregon 12, 20, 24, 25, 46, 48, 58

southern 20

Pacific Coast 20

Pacific Northwest 15, 48, 51

Piedmont 61

Rocky Mountain 15

Rocky Mountain States 20

South Carolina 25, 46

Southeastern 15, 19, 20, 23, 24, 60

Southern U.S. 60

Southwest 20, 51

Tennessee 25, 41, 46
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-42-vol. 5. 2002 79

Texas 24, 25, 60

Utah 25, 46

Virginia 25, 60

Washington 20, 24, 25, 46, 48, 58

Western Regional Air Partnership

(WRAP) 14, 26, 40, 41, 67

Western U.S. 15, 19

Wyoming 25, 39

Yellowstone National Park 20

Utah. See United States of America: Utah

V

Virginia. See United States of America: Virginia

visibility 2, 4, 6, 7, 10, 13, 14, 15, 19, 20, 24, 25, 26, 35,

39, 41, 45, 49, 50, 58, 59, 60, 64, 65, 66

Class I

areas 10, 12, 14, 15, 24, 25, 47, 49, 50, 58, 59, 65

visibility impairment and reduction 1, 20, 46, 58, 60

VISTAS. See regional planning organizations

VSMOKE. See models

W

Washington. See United States of America: Washington

welfare 2, 4, 6, 9, 11, 16, 35, 45, 55, 58, 66

Western Regional Air Partnership (WRAP) 14, 67

World

Africa

tropical 24

Asia

tropical 24

Canada 20, 25, 42, 49

Russia 25

South America

tropical 25

WRAP. See Western Regional Air Partnership (WRAP)

Wyoming. See United States of America: Wyoming

Y

Yellowstone National Park. See United States of America:

Yellowstone National Park
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The Rocky Mountain Research Station develops scientific information

and technology to improve management, protection, and use of the

forests and rangelands. Research is designed to meet the needs of

National Forest managers, Federal and State agencies, public and

private organizations, academic institutions, industry, and individuals.

Studies accelerate solutions to problems involving ecosystems,

range, forests, water, recreation, fire, resource inventory, land reclamation, community sustainability, forest engineering technology,

multiple use economics, wildlife and fish habitat, and forest insects

and diseases. Studies are conducted cooperatively, and applications

may be found worldwide.

Research Locations

Flagstaff, Arizona Reno, Nevada

Fort Collins, Colorado* Albuquerque, New Mexico

Boise, Idaho Rapid City, South Dakota

Moscow, Idaho Logan, Utah

Bozeman, Montana Ogden, Utah

Missoula, Montana Provo, Utah

Lincoln, Nebraska Laramie, Wyoming

*Station Headquarters, Natural Resources Research Center,

2150 Centre Avenue, Building A, Fort Collins, CO 80526

RMRS

ROCKY MOUNTAIN RESEARCH STATION