Determining Base Camp 

Personnel Exposures to 

Carbon Monoxide during 

Wildland Fire Suppression 

Activities – California

Robert E. McCleery, MSPH, CIH

Anthony Almazan, MD

Chad H. Dowell, MS, CIH

John Snawder, PhD, DABT

Health Hazard Evaluation Report

HETA 2008-0245-3127

May 2011

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

Workplace

Safety and Health

 National Institute for Occupational 

Safety and Health

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific 

facility evaluated and may not be universally applicable. Any recommendations made are not to be 

considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE 

reports are available at http://www.cdc.gov/niosh/hhe/
The employer shall post a copy of this report 

for a period of 30 calendar days at or near 

the workplace(s) of affected employees. The 

employer shall take steps to insure that the 

posted determinations are not altered, defaced, 

or covered by other material during such 

period. [37 FR 23640, November 7, 1972, as 

amended at 45 FR 2653, January 14, 1980].
Health Hazard Evaluation Report 2008-0245-3127 Page i

Appendix A

Report Abbreviations................................................................................................ii

Highlights of the NIOSH Health Hazard Evaluation........................iii

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

Introduction ...................................................................................................1

Assessment.....................................................................................................2

Results..............................................................................................................3

Discussion.......................................................................................................8

Conclusions................................................................................................. 10

Recommendations.................................................................................... 11

References.................................................................................................... 13

Contents

Methods........................................................................................................ 16

Occupational Exposure Limits and Health Effects......................... 18

Acknowledgments

Appendix B

Acknowledgments and Availability of Report................................ 30

Appendix C Tables............................................................................................................. 24

Appendix D Figures........................................................................................................... 26
Page ii Health Hazard Evaluation Report 2008-0245-3127

Abbreviations

ACGIH® American Conference of Governmental Industrial Hygienists

A/C Air-conditioning

BEI® Biological exposure index

CFR Code of Federal Regulations

CMD Command

CO Carbon monoxide

COHb Carboxyhemoglobin

COMM Communications

EPA Environmental Protection Agency

GA General area

HHE Health hazard evaluation

IDLH Immediately dangerous to life and health

NAAQS National Ambient Air Quality Standard

NAICS North American Industry Classification System

NIOSH National Institute for Occupational Safety and Health

OEL Occupational exposure limit

OSHA Occupational Safety and Health Administration

PBZ Personal breathing zone

PEL Permissible exposure limit

ppm Parts per million

REL Recommended exposure limit

STEL Short-term exposure limit

TLV® Threshold limit value

TWA Time-weighted average

WEEL Workplace environmental exposure limits

WHO World Health Organization
Health Hazard Evaluation Report 2008-0245-3127 Page iii

The National Institute 

for Occupational Safety 

and Health (NIOSH) 

received a request for a 

health hazard evaluation 

(HHE) at a base camp 

supporting the Siskiyou 

and Ukonom fires in the 

Klamath National Forest, 

California. Federal 

agency managers 

submitted the request 

due to concerns about 

carbon monoxide (CO) 

exposures of personnel 

working at base camps 

who support firefighters 

during wildland fire 

suppression activities.

Highlights of the

NIOSH Health

Hazard Evaluation

What NIOSH Did

● We evaluated the base camp in August 2008.

● We measured base camp employee’s exposure to CO 

in the air and blood. CO in the blood was measured as 

carboxyhemoglobin (COHb).

● We measured temperature, relative humidity, and dew point 

temperatures in the base camp.

What NIOSH Found

● Most base camp employees’ CO exposure levels were very low.

● Some base camp employees’ CO exposure levels were over 

peak occupational exposure limits.

● Most COHb measurements were very low. Three out of 

19 base camp employees who did not smoke had COHb 

measurements that were slightly elevated.

What Managers Can Do

● Develop a program to measure base camp employees’ 

exposure to CO and particulates.

● Think about developing CO and particulate action levels for 

use in future fire events. If used, make sure to account for 

extended work shifts.

● Implement a program to raise awareness about heat stress.

● Limit the number of employees working extended work 

shifts. If extended work shifts are needed, make sure these 

employees get adequate rest and recovery time.

What Employees Can Do

● Avoid working near sources of CO. Other sources of CO in 

the base camp include gasoline- and diesel-powered vehicles 

and equipment and cigarette smoke.

● Tell your supervisor if you feel weak, nauseated, excessively 

fatigued, confused, or irritable. These are signs of heat 

illness.

● Drink plenty of fluids to prevent heat-related illness
Page iv Health Hazard Evaluation Report 2008-0245-3127

Overall, CO air 

concentrations and 

employee COHb 

measurements were 

low. However, some 

peak CO concentrations 

exceeded relevant OELs. 

Although not directly 

comparable to the ACGIH 

BEI because of the use of 

16-hour work shifts, some 

nonsmoking employees 

met or exceeded a COHb 

measurement of 3.5%. We 

recommend developing a 

base camp air monitoring 

program for particulates 

and CO, establishing a 

heat stress awareness 

program, and limiting 

extended work shifts.

Summary

In July 2008, NIOSH received a request for an HHE at a base 

camp supporting the Siskiyou and Ukonom fires in the Klamath 

National Forest, California. Federal agency managers submitted 

the request due to concerns about CO exposure among 

personnel who work in the base camp supporting wildland 

firefighters during fire suppression activities. Headaches were 

listed as the primary health concern.

On August 13–14, 2008, NIOSH investigators conducted PBZ 

air monitoring for CO exposure and measured blood COHb 

levels for 19 nonsmoking forestry personnel and contractors 

and performed GA air sampling for CO in the base camp. 

Employees’ average work shift CO exposures were low (< 6 

ppm). However, peak CO concentrations exceeded OELs; 7 of 

19 (37%) exceeded the ACGIH excursion limit of 125 ppm, 

5 of 19 (26%) exceeded the NIOSH ceiling limit of 200 ppm, 

and 4 of 19 (21%) exceeded the 1000 ppm upper limit of the 

instrument (approaching the 1200 ppm NIOSH IDLH level 

for < 1 minute). The GA monitors located throughout the base 

camp indicated average CO concentrations of less than 2 ppm 

with a peak reading of 20 ppm.

Over the 2-day period, 19 nonsmoking employees had COHb 

measurements taken. Although not directly comparable to 

the ACGIH BEI (end of shift, 8-hour COHb measurement 

of 3.5%), 3 of the 19 (16%) nonsmoking employees met or 

exceeded a COHb measurement of 3.5%, an indicator of a 25 

ppm, 8-hour TWA CO exposure. Only one of these employees 

had a corresponding peak PBZ air CO concentration exceeding 

the ACGIH excursion limit and none had a corresponding 

peak PBZ air CO concentration that exceeded the NIOSH 

ceiling limit. The levels of COHb we found among employees 

at the base camp have not been documented to cause symptoms 

that can result from short-term, higher levels of CO exposure. 

However, the combination of consecutive 16-hour work 

shifts, continuous exposure to forest fire smoke, and hot 

environmental conditions could explain headaches reported in 

the HHE request.
Health Hazard Evaluation Report 2008-0245-3127 Page v

Summary (continued)

Keywords: NAICS 924120 (Administration of Conservation 

Programs), carbon monoxide, CO, carboxyhemoglobin, COHb, base 

camp, firefighter, wildland forest fire 

NIOSH investigators recommend developing a base camp air 

monitoring program for particulates and CO and limiting 

the number of personnel working extended shifts as well as 

the frequency and duration of extended work shifts. We also 

recommend developing CO and particulate action levels for use 

during future fire events, taking into consideration employee 

extended work shifts. A program should also be established to 

increase base camp personnel’s awareness of heat stress.
Page 1 Health Hazard Evaluation Report 2008-0245-3127

Introduction

In July 2008, NIOSH received a request for an HHE at a base camp 

supporting the Siskiyou and Ukonom fires in the Klamath National 

Forest, California, during the summer of 2008. Federal agency 

managers submitted the HHE request because of their concern about 

potential CO exposures among the personnel working in base camps 

supporting wildland firefighters during fire suppression activities.

In response to this request, NIOSH investigators conducted an 

investigation at the base camp on August 13 and 14, 2008. The 

investigation included GA and PBZ CO air monitoring of forestry 

personnel and contractors and monitoring of COHb, a biological 

indicator of CO exposure. This report summarizes our evaluation 

and provides recommendations for a more healthy work environment 

for base camp personnel.

Background

Klamath National Forest covers approximately 1.7 million acres 

in northern California and southern Oregon [USFS 2008]. The 

forest consists of Ponderosa pine, Douglas fir, sub-alpine fir, and 

mixed conifer. The Siskiyou and Ukonom forest fires began by 

lightning strikes in late June 2008. Combining all fires in the area, 

approximately 200,000 acres burned.

The base camp was located in California in the Klamath River Valley 

of the Klamath National Forest. This base camp housed the incident 

command post and was a firefighter staging area for fire suppression 

operations. The base camp included parking, daily briefing, and 

crew camping areas (personal tents and sleeping trailers); facilities for 

dining and showering; laundry and medical services; supply dispersal; 

vehicle inspection, fueling, and washing areas; and tents and trailers 

for administrative services, such as communications, planning, 

logistics, safety, and finance. Diesel generators provided power for 

tents, trailers, air-conditioning (window A/C units, swamp coolers, 

and trailer-mounted A/C units), and other base camp equipment.

At the base camp, forestry and contractor personnel and firefighters 

were grouped into incident management teams consisting of 

command, supply, medical, communications, and support services. 

Support services included caterers, camp crew, ground, latrine, 

shower, and camp security. Base camp personnel worked up to 16-

hour shifts. The base camp closed on September 26, 2008.
Health Hazard Evaluation Report 2008-0245-3127 Page 2

We measured CO air concentrations on 19 nonsmoking employees 

(communication, command, medical, resource, and supply staff; 

caterers; reefers; and mechanics) during the entire 16-hour work 

shift on August 13, 2008; during the overnight period to evaluate 

CO concentrations while they slept in their tents (monitors 

remained beside them); and 6–8 hours during the work shift on 

August 14, 2008. Additionally, we placed 13 GA CO monitors in 

base camp locations such as the security area (south), tent camp 

areas, and various administration tents/trailers.

In association with measuring CO air concentrations, we collected 

noninvasive measurements of COHb on nonsmokers using a 

pulse CO-oximeter. We collected these measurements close to 

the beginning of each work shift, at various times during the 

work shift, and at the end of the work shift. We excluded current 

smokers from this measurement since smokers have been shown to 

have elevated background COHb levels.

We used a weather station to collect climate information 

(temperature, relative humidity, dew point, and other variables) at 

the base camp during the entire evaluation. 

You can find additional details about these sampling methods in 

Appendix A and a discussion of OELs and adverse health effects 

from CO exposure in Appendix B.

Assessment
Page 3 Health Hazard Evaluation Report 2008-0245-3127

Results

Carbon Monoxide in Air

Table 1 provides a summary of real-time PBZ CO air sampling 

results, while Appendix C, Table C1, presents each individual’s 

PBZ CO air sampling results for the August 13, 2008, work shift, 

the overnight period, and 6–8 hours of the August 14, 2008, work 

shift. As Table 1 indicates, the employees’ average CO exposures 

over their work shift were low (< 6 ppm), but some peak CO 

concentrations were above relevant OELs. Seven of 19 (37%) peak 

CO exposures exceeded the ACGIH excursion limit of 125 ppm, 5 

of 19 (26%) exceeded the NIOSH ceiling limit of 200 ppm, and 4 

of 19 (21%) exceeded the 1000 ppm upper limit of the instrument 

(approaching the 1200 ppm NIOSH IDLH level for < 1 minute). 

The overnight CO air sampling results provided in Table C1 also 

indicate low average concentrations of CO (range: 0.12–5.7 ppm). 

Appendix D, Figures D1–D7 graphically present the real-time CO 

concentration data for each individual with peak exposures above 

relevant OELs.

Table 1. Base camp personnel – summary of CO concentrations (ppm) from August 13–14, 2008.

Job N (shifts) 1st Shift* Overnight*† 2nd Shift*

Avg. Peak Avg. Peak Avg. Peak

Caterer 3 (6) 2.6 107 2.5 > 1000‡§ 2.1 28

Command 2 (4) 1.1 12 1.1 2.9 2.0 74

Communications¶ 2 (3) 2.8 > 1000‡§ 1.5 15 2.4 8.6

Mechanic¶ 2 (4) 4.8 > 1000‡§** 2.2 7.3 3.2 72

Medical 1 (2) 2.7 49 1.3 3.9 1.5 8.0

Reefer¶ 3 (3) 2.6 > 1000‡§ 0.30 22 — —

Resource 1 (2) 2.3 141‡ 0.57 5.8 1.9 15

Supply/Logistics 1 (2) 1.1 8.6 1.4 5.5 2.0 15

Supply 3 (6) 1.1 45 2.0 80 3.0 128‡

Weed Wash 1 (1) — — — — 5.4 40

N = Number of employees (number of total work shifts)

* = Approximate duration – 1st shift (16 hours), overnight (8 hours), 2nd shift (monitored 6–8 hours)

† = Employees kept their CO monitor beside them in their tent while they slept.

‡ = Exceeded the ACGIH excursion limit of 125 ppm

§ = Exceeded the NIOSH ceiling limit of 200 ppm

¶ = 1 of 2 communications employees had 2nd shift data; 1 of 2 mechanics and 2 of 3 reefers had overnight data.

** = Both mechanics exceeded ACGIH excursion and NIOSH ceiling limits (423 ppm and > 1000 ppm).
Health Hazard Evaluation Report 2008-0245-3127 Page 4

Table C2 provides the real-time CO concentrations of the GA 

monitors placed in numerous areas in and around the base camp. 

These GA monitors indicated average CO concentrations of 

less than 3 ppm, with the highest peak reading of 20 ppm in the 

east end of the base camp. Although EPA does not have a 24-

hour limit for CO, the average CO concentrations of these GA 

monitors are well under the EPA NAAQS 8-hour limit of 9 ppm. 

Figure 1 provides real-time CO concentration data from the north 

end of the base camp over the entire evaluation period. The CO 

concentrations measured in this area are similar to the other GA 

locations and indicate that the visual buildup of smoke in the base 

camp (Figures 2–4) does not equate to a high CO concentration in 

the monitored areas.

Results

 (continued)

Figure 1. Outdoor CO concentrations at the base camp’s north end on 

August 13–14, 2008.

Figures 2–4 illustrate the smoke buildup in the base camp during 

our evaluation. Figures 2 and 3 are photographs taken in the same 

location and looking in the same direction only a few hours apart 

(approximately 8:30 a.m. and 10:00 a.m.). Smoke buildup in the 

valley where the base camp was located is clearly visible in these 

figures. The far mountain range is visible in Figure 2, but not as 

easily discernable in Figure 3. Additionally, the smoke had settled 

deeper into the valley by midmorning as seen in Figure 3. Figure 

4 is the base camp in the early morning hours (approximately 7:30 

a.m.) on August 14, 2008.
Page 5 Health Hazard Evaluation Report 2008-0245-3127

Results

 (continued)

Figure 2. Early morning smoke (approximately 8:30 a.m.) in the base 

camp on August 13, 2008.

Figure 3. Midmorning smoke (approximately 10:00 a.m.) in the base 

camp on August 13, 2008.
Health Hazard Evaluation Report 2008-0245-3127 Page 6

Results

 (continued)

Figure 4. Early morning smoke (approximately 7:30 a.m.) in the base 

camp on August 14, 2008.

Carboxyhemoglobin in Blood

Over the 2-day period, 19 nonsmoking employees had COHb 

measurements taken. Although not directly comparable to the 

ACGIH BEI (end of shift, 8-hour COHb measurement of 3.5%), 3 

of 19 (11%) nonsmoking employees (reefer, resources, and supply/

logistics personnel) met or exceeded a COHb measurement of 

3.5%, which is considered an indicator of a 25-ppm, 8-hour TWA 

CO exposure. One employee showed a progressive increase in 

COHb that exceeded 3.5% in the late evening of August 13, 2008, 

returned to 1% at the start of the next day, and then increased 

again above 3.5% during the next day’s work shift. This employee 

had one measured peak CO concentration above the ACGIH 

excursion limit of 125 ppm during the late morning of August 

13, 2008, but had average CO exposures below 3 ppm during 

the two work shifts and overnight. The other two employees with 

COHb readings at or above 3.5% did not have any measured CO 

concentrations exceeding relevant OELs. All three employees, as 

with all tested employees, had low average PBZ CO exposures.
Page 7 Health Hazard Evaluation Report 2008-0245-3127

Results

 (continued) Environmental Data

Figure 5 presents temperature, relative humidity, and dew point 

temperature data collected during the site visit. The data show that 

the August 13, 2008, afternoon air temperature reached 100oF, 

dew point temperature ranged between 50oF and 55oF, and relative 

humidity was consistently around 20% during the afternoon 

(the hottest part of the day). During the evening hours, the air 

temperature changed over 40oF as the August 14, 2008, morning 

temperature was approximately 57oF. At the end of the evaluation 

on August 14, 2008, the daytime air temperature was 90oF. It is 

important to note that the daytime relative humidity dropped to 

20%, indicating an environment that many people would perceive 

as dry.

Figure 5. Outdoor environmental data collected at the base camp’s 

north end – temperature, dew point temperature, and relative humidity 

measurements on August 13–14, 2008.
Health Hazard Evaluation Report 2008-0245-3127 Page 8

Discussion

During our evaluation, average CO air concentrations measured 

on employees were low (< 3 ppm), although some base camp 

personnel had brief peak CO exposures exceeding relevant 

OELs including a few in excess of 1000 ppm. However, these 

elevated peak exposures were all very short duration (< 1 minute). 

The elevated peak CO concentrations could have been a result 

of the job task for the day (e.g., mechanic conducting vehicle 

maintenance) and/or the location of an employee in the base camp 

(e.g., supply area in close proximity to vehicles moving in or out 

of the base camp). Although there were obvious sources of CO in 

addition to the fires (i.e., vehicle exhaust and three 3,000-watt gas 

generators), most sources of power in the base camp were diesel 

generators, which, if maintained properly, should not emit CO at 

concentrations found in our peak measurements. Radio frequency 

signals from the use of two-way radios could have caused a spike 

in the signal that was recorded as a CO peak, as this is a known 

interference for the CO monitors [NIOSH 2000]. It was not 

possible to collect detailed information on the location of all base 

camp personnel during the day due to the size of the camp and 

number of base camp personnel. Thus, we were unable to correlate 

every activity with a particular CO concentration.

The nature of this type of work makes interpretation of our CO 

and COHb results difficult. Employees typically worked 16-hour 

shifts in the base camp, their nonwork time continues in the 

base camp, and CO exposure continues during the overnight 

hours, essentially maintaining some low level of exposure to CO 

for a continuous 24-hour period. This nontraditional work shift 

complicates comparing employee exposures to OELs established 

for a typical 8- to 10-hour work shift and 40-hour workweek. 

Additional factors – such as, a long and busy fire season, an 

individual’s potential for numerous deployments to base camps, 

the varying distances from the base camp to the forest fire, many 

consecutive 16-hour workdays without a break (time or day off) 

from exposure, and the varying environmental conditions – further 

complicates the measurement and interpretation of potential CO 

exposures.

COHb measurements were for the most part consistent with 

ambient CO levels; that is, low COHb levels reflected low ambient 

CO concentrations. However, there were a few elevated COHb 

readings among base camp personnel. The elevated COHb 

readings may have been a result of an unrecognized CO source, 

equipment inaccuracy, unreported smoking, or operator error.
Page 9 Health Hazard Evaluation Report 2008-0245-3127

Discussion

 (continued) Exposure to low ambient CO concentrations has been reported 

to affect multiple body systems, but most studies involved 

shorter periods with continuous levels of CO exposure, unlike 

the exposures at the base camp. There is limited evidence that 

volunteers exposed to CO have shown subtle brain function 

changes when COHb levels are about 5% [EPA 1979, 1984]. These 

changes in brain function involved tasks that required sustained 

attention or performance, such as hand-eye coordination and 

detection of infrequent events. Some research has found that lowlevel CO exposure affects exercise performance, but other studies 

have not found this effect. In the 1970s, COHb levels between 

2.5% and 4% were found to decrease maximal exercise duration in 

young healthy men in the short term [Aronow and Cassidy 1975]. 

However, no studies have been published that have examined 

longer-term effects of low-level exposure to CO on exercise 

duration. At slightly higher levels than we found at the base camp, 

two researchers found that short-term CO inhalation producing a 

COHb of 6.9% had no significant effect on the cardiovascular or 

respiratory responses of young healthy men [Turner and McNicol 

1993]. The levels of COHb we found among employees at the 

base camp have not been reported to cause the symptoms that can 

occur with short-term, higher levels of CO exposure. However, 

the combination of consecutive 16-hour work shifts, continuous 

exposure to forest fire smoke, and hot environmental conditions 

could explain headaches reported in the HHE request among some 

base camp personnel.

Extended work shifts themselves may result in employee stress, 

fatigue, decreased concentration, deteriorating performance, and 

other adverse effects. OSHA suggests that management should 

limit the amount of time employees work extended shifts and, if 

extended shifts are unavoidable, ensure employees have enough 

time for rest and recovery [OSHA 2004]. NIOSH provides 

additional information and guidance on their work schedule 

topic page “Work Schedules: Shift Work and Long Work Hours” 

[NIOSH 2010] and in the publication Overtime and Extended 

Work Shifts: Recent Findings on Illnesses, Injuries and Health 

Behaviors [NIOSH 2004].
Health Hazard Evaluation Report 2008-0245-3127 Page 10

Discussion

 (continued) The environmental conditions measured during this evaluation 

indicate a potential for heat stress and strain. High temperatures 

may lead to heat-related illnesses if base camp personnel are 

working outside air-conditioned tents or trailers for extended 

periods. An agency-established heat awareness program is 

recommended for base camp personnel as a method of prevention 

and a continuing reminder of the potential for heat-related illness 

while on duty.

Although this evaluation focused on CO exposures, base camp 

personnel also expressed a concern about particulate exposures. 

Numerous studies of firefighter (less extensive for base camp 

personnel) exposures to wildland fire smoke and its constituents, 

including CO and particulates, have been published [NIOSH 

1992a,b,c, 1994, 2000; Materna et al. 1992; USDA 1999, 2000a,b; 

Reinhardt and Ottmar 2004; Gaughan et al. 2008].

Although average CO concentrations measured on base camp 

personnel were low, peak exposures exceeding relevant OELs did 

occasionally occur. In most cases, COHb measurements reflected 

the low personal CO exposure concentrations and the low ambient 

CO concentrations found. Although not directly comparable to 

the ACGIH BEI because of 16-hour work shifts, some nonsmoking 

employees met or exceeded a COHb measurement of 3.5%. The 

combination of consecutive 16-hour work shifts, 24-hour low-level 

exposure to CO, exposure to other contaminants in forest fire 

smoke, and hot environmental conditions could result in adverse 

health effects among base camp personnel; efforts should be made 

to minimize exposures.

Conclusions
Page 11 Health Hazard Evaluation Report 2008-0245-3127

Recommendations

Based on our findings, we recommend the actions listed below to 

create a more healthful workplace. We encourage the agency to use 

a labor-management health and safety committee or working group 

to discuss the recommendations in this report and develop an 

action plan. Those involved in the work can best set priorities and 

assess the feasibility of our recommendations for the agency-specific 

situation. Our recommendations are based on the hierarchy of 

controls approach (refer to Appendix B: Occupational Exposure 

Limits and Health Effects). This approach groups actions by their 

likely effectiveness in reducing or removing hazards. In most cases, 

the preferred approach is to eliminate hazardous materials or 

processes and install engineering controls to reduce exposure or 

shield employees. Until such controls are in place, or if they are 

not effective or feasible, administrative measures and/or personal 

protective equipment may be needed.

Administrative Controls

Administrative controls are management-dictated work practices 

and policies to reduce or prevent exposures to workplace hazards. 

The effectiveness of administrative changes in work practices 

for controlling workplace hazards is dependent on management 

commitment and employee acceptance. Regular monitoring and 

reinforcement is necessary to ensure that control policies and 

procedures are not circumvented in the name of convenience or 

production.

1. Develop a base camp air monitoring program during a future 

fire season that would include particulate exposure monitoring 

in addition to CO.

● Include monitoring of COHb levels in employees using a 

pulse CO-oximeter, exhaled breath CO analysis [ACGIH 

2001], or both.

● Refer to the previous wildland firefighter studies referenced 

in this report for guidance on environmental sampling 

methods used to evaluate exposures to CO and particulates 

in addition to other potential contaminants.

● Consider developing CO and particulate action levels 

to reduce exposure during future fire events, taking into 

consideration employees’ extended work shifts. For example, 

an action level would trigger a removal of the employee from 

the base camp for a designated period or relocation of the 

base camp to another area.
Health Hazard Evaluation Report 2008-0245-3127 Page 12

2. Establish a heat stress awareness program and refer to the 

NIOSH criteria on hot work environments [NIOSH 1986]. This 

program should include the following components:

● Monitoring the environmental heat in the base camp.

● Briefing base camp personnel on the day’s weather forecast 

and the potential for a heat alert.

● Ensuring that, during difficult environmental conditions, 

personnel stay inside cooled tents or trailers as much as 

possible and drink fluids to remain hydrated.

● Training employees on the hazards of heat stress, signs and 

symptoms of heat-related illness and first-aid procedures 

for treatment, and preventive measures and employee 

responsibilities to avoid heat stress.

● Informing a supervisor if an employee feels weak, nauseated, 

excessively fatigued, confused, and/or irritable.

3. Limit the number of personnel working extended work shifts 

and the frequency/duration of extended work shifts. When 

extended work shifts are necessary, ensure adequate rest and 

recovery time. Refer to NIOSH and OSHA guidance on 

extended work shifts [NIOSH 2004; OSHA 2004].

Recommendations

 (continued)
Page 13 Health Hazard Evaluation Report 2008-0245-3127

References

ACGIH [2001]. Documentation of threshold limit values and 

biological exposure indices. 7th edition. Cincinnati, OH: 

American Conference of Governmental Industrial Hygienists.

Aronow WS, Cassidy J [1975]. The effect of carbon monoxide on 

maximal treadmill exercise. A study of normal persons. Ann Intern 

Med 83(4):496–500.

EPA [1979]. Air quality criteria for carbon monoxide. Research 

Triangle Park, NC: U.S. Environmental Protection Agency, Office 

of Health and Environmental Assessment, Environmental Criteria 

and Assessment Office, EPA Report No. EPA-600/8-79-022, NTIS 

No. PB81-244840.

EPA [1984]. Revised evaluation of health effects associated with 

carbon monoxide exposure: an addendum to the 1979 EPA air 

quality criteria document for carbon monoxide. Research Triangle 

Park, NC: U.S. Environmental Protection Agency, Office of Health 

and Environmental Assessment, Environmental Criteria and 

Assessment Office, EPA Report No. EPA 600/8-83-033F, NTIS 

No. PB85-103471.

Gaughan DM, Cox-Ganser JM, Enright PL, Castellan RM, Wagner 

GR, Hobbs GR, Bledsoe TA, Siegel PD, Kreiss K, Weissman DN 

[2008]. Acute upper and lower respiratory effects in wildland 

firefighters. J Occup Environ Med 50(9):1019–1028.

Materna BL, Jones JR, Sutton PM, Rothman N, Harrison RJ 

[1992]. Occupational exposures in California wildland fire fighting. 

Am Ind Hyg Assoc J 53(1):69–76.

NIOSH [1986]. Criteria for a recommended standard: 

occupational exposure to hot environments, rev. Cincinnati, OH: 

U.S. Department of Health and Human Services, Centers for 

Disease Control, National Institute for Occupational Safety and 

Health, DHHS (NIOSH) Publication No. 86-113.

NIOSH [1992a]. Hazard evaluation and technical assistance report: 

U.S. Department of the Interior, National Park Service, Gallatin 

National Forest, Montana. By Kelly JE. Cincinnati, OH: U.S. 

Department of Health and Human Services, Centers for Disease 

Control and Prevention, National Institute for Occupational Safety 

and Health, NIOSH HETA Report No. 91-312-2185.
Health Hazard Evaluation Report 2008-0245-3127 Page 14

NIOSH [1992b]. Hazard evaluation and technical assistance 

report: U.S. Department of the Interior, National Park Service, 

New River Gorge National River, West Virginia. By Kelly JE. 

Cincinnati, OH: U.S. Department of Health and Human Services, 

Centers for Disease Control and Prevention, National Institute 

for Occupational Safety and Health, NIOSH HETA Report No. 

92-045-2260.

NIOSH [1992c]. Hazard evaluation and technical assistance 

report: U.S. Department of the Interior, National Park Service, 

Yellowstone National Park, Wyoming. By Reh CM, Deitchman S. 

Cincinnati, OH: U.S. Department of Health and Human Services, 

Centers for Disease Control and Prevention, National Institute 

for Occupational Safety and Health, NIOSH HETA Report No. 

88-320-2176.

NIOSH [1994]. Hazard evaluation and technical assistance report: 

U.S. Department of the Interior, National Park Service, Yosemite 

National Park, California. By Reh CM, Letts D, Deitchman S. 

Cincinnati, OH: U.S. Department of Health and Human Services, 

Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, NIOSH HETA Report No. 90-

0365-2415.

NIOSH [2000]. Hazard evaluation and technical assistance 

report: Colorado Department of Public Health and Environment, 

Colorado. By McCammon JB, McKenzie L. Cincinnati, OH: U.S. 

Department of Health and Human Services, Centers for Disease 

Control and Prevention, National Institute for Occupational Safety 

and Health, NIOSH HETA Report No. 98-0173-2782.

NIOSH [2004]. Overtime and extended work shifts: recent 

findings on illnesses, injuries, and health behaviors. By Caruso 

CC, Hitchcock EM, Dick RB, Russo JM, Schmit JM. Cincinnati, 

OH: U.S. Department of Health and Human Services, Centers 

for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, DHHS (NIOSH) Publication No. 

2004-143.

NIOSH [2010]. Work schedules: shift work and long work hours. 

[www.cdc.gov/niosh/topics/ workschedules/]. Date accessed: April 

2011.

References

 (continued)
Page 15 Health Hazard Evaluation Report 2008-0245-3127

OSHA [2004]. Extended/unusual workshifts. [www.osha.gov/

SLTC/emergencypreparedness/ guides/extended.html]. Date 

accessed: April 2011.

Reinhardt TE, Ottmar RD [2004]. Baseline Measurements of 

smoke exposure among wildland firefighters. J Occup Environ Hyg 

1(9):593–606.

Turner JA, McNicol MW [1993]. The effect of nicotine and carbon 

monoxide on exercise performance in normal subjects. Respir Med 

87(6):421–431.

USDA [1999]. Guide to monitoring smoke exposure of wildland 

firefighters. By Reinhardt TE, Ottmar RD, Hallett MJ. Portland, 

OR: U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station, Pacific Northwest General Technical 

Report PNW-GTR-448.

USDA [2000a]. Smoke exposure among firefighters at prescribed 

burns in the Pacific Northwest. By Reinhardt TE, Ottmar RD, 

Hanneman AJS. Portland, OR: U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station, Pacific 

Northwest Research Paper PNW-RP-526.

USDA [2000b]. Smoke exposure at western wildfires. By Reinhardt 

TE, Ottmar RD. Portland, OR: U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station, Pacific 

Northwest Research Paper PNW-RP-525.

USFS [2008]. Klamath National Forest. [www.fs.fed.us/r5/

klamath/about/index.shtml]. Date accessed: April 2011.

References

 (continued)
Health Hazard Evaluation Report 2008-0245-3127 Page 16

Appendix A: Methods 

Carbon Monoxide in Air

We measured CO air concentrations in the PBZ of base camp personnel and at GA work locations using 

ToxiUltra Atmospheric Monitors (Biosystems, Inc., Middletown, Connecticut) with CO sensors. All 

ToxiUltra CO monitors were zeroed and calibrated before each use, according to the manufacturer’s 

recommendations. These monitors are direct-reading instruments with data-logging capabilities. The 

instruments were operated in the passive diffusion mode, with a 1-minute sampling interval. The 

instruments have a nominal range from 0 to 500 ppm with a maximum instantaneous reading of 1000 

ppm.

Additional GA air samples for CO were collected using five RAE Systems AreaRAE monitors (Rae® 

Systems, San Jose, California). AreaRAEs are multigas monitors that measure specific substances, such as 

CO, using electrochemical cells. The monitors are capable of wireless operation and real-time data transfer 

to a base controller.

Carboxyhemoglobin in Blood

We collected noninvasive measurements of COHb on base camp personnel using a Masimo® Rad-57 

signal extraction pulse CO-OximeterTM (Masimo Corporation, Irvine, California). This instrument uses 

a finger sensor that emits wavelengths of light to collect and analyze physiological data and determine 

COHb levels. The U.S. Food and Drug Administration approves its use for the measurement of COHb. 

The manufacturer states the instrument measures COHb in the range of 1%–40% with an accuracy of 

+/- 3% [Masimo 2008]. The test is painless and takes approximately 10 to 15 seconds to perform a single 

reading. Unlike exhaled breath CO testing, this instrument allows noninvasive measurement of COHb 

without subject cooperation or effort. Pulse CO-oximetry has been shown to be a reliable method of 

measuring COHb [Mottram et al. 2005; Barker et al. 2006; Hampson et al. 2006; Chee et al. 2008; Suner 

et al. 2008; Suner and McMurdy 2009].

Environmental Data

A HOBO® Weather Station (Onset Computer Corporation, Bourne, Massachusetts) was used to collect 

climate information (temperature, relative humidity, dew point) at the base camp during the entire site 

visit. This data logger is capable of measuring and storing data for up to 15 different parameters. 
Page 17 Health Hazard Evaluation Report 2008-0245-3127

References

Barker S, Curry J, Redford D, Morgan S [2006]. Measurement of carboxyhemoglobin and methemoglobin 

by pulse oximetry. Anesthesiology 105(5):892–897.

Chee K, Nilson D, Partridge R, Hughes A, Suner S, Sucov A, Jay G [2008]. Finding needles in a haystack: 

a case series of carbon monoxide poisoning detected using new technology in the emergency department. 

Clin Toxicol 46(5):461–469.

Hampson N, Ecker E, Scott K [2006]. Use of a noninvasive pulse CO-oximeter to measure blood 

carboxyhemoglobin levels in bingo players. Respir Care 51(7):758–760.

Masimo Corporation [2008]. Breakthrough noninvasive patient monitoring technologies. [www.masimo.

com/]. Date accessed: April 2011.

Mottram C, Hanson L, Scanlon P [2005]. Comparison of the Masimo Rad57 pulse oximeter with SpCO 

technology against a laboratory CO-oximeter using arterial blood. Respir Care 50(11):1471.

Suner S, McMurdy J [2009]. Masimo Rad-57 Pulse CO-OximeterTM for noninvasive carboxyhemoglobin 

measurement. Expert Rev Med Devices 6(2):125–130.

Suner S, Partridge R, Sucov A, Valente J, Chee K, Hughes A, Jay G [2008]. Non-invasive pulse COoximetry screening in the emergency department identifies occult carbon monoxide toxicity. J Emerg Med 

34(4):441–450.

Appendix A: Methods (continued)
Health Hazard Evaluation Report 2008-0245-3127 Page 18

Appendix B: Occupational Exposure Limits and Health Effects

In evaluating the hazards posed by workplace exposures, NIOSH investigators use both mandatory (legally 

enforceable) and recommended OELs for chemical, physical, and biological agents as a guide for making 

recommendations. OELs have been developed by federal agencies and safety and health organizations to 

prevent the occurrence of adverse health effects from workplace exposures. Generally, OELs suggest levels 

of exposure that most employees may be exposed to for up to 10 hours per day, 40 hours per week, for a 

working lifetime, without experiencing adverse health effects. However, not all employees will be protected 

from adverse health effects even if their exposures are maintained below these levels. A small percentage 

may experience adverse health effects because of individual susceptibility, a preexisting medical condition, 

and/or a hypersensitivity (allergy). In addition, some hazardous substances may act in combination with 

other workplace exposures, the general environment, or with medications or personal habits of the 

employee to produce adverse health effects even if the occupational exposures are controlled at the level set 

by the exposure limit. Also, some substances can be absorbed by direct contact with the skin and mucous 

membranes in addition to being inhaled, which contributes to the individual’s overall exposure.

Most OELs are expressed as a TWA exposure. A TWA refers to the average exposure during a normal 8- 

to 10-hour workday. Some chemical substances and physical agents have recommended STEL or ceiling 

values where adverse health effects are caused by exposures over a short period. Unless otherwise noted, 

the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday, and 

the ceiling limit is an exposure that should not be exceeded at any time.

In the United States, OELs have been established by federal agencies, professional organizations, state 

and local governments, and other entities. Some OELs are legally enforceable limits, while others are 

recommendations. The U.S. Department of Labor OSHA PELs (29 CFR 1910 [general industry]; 29 

CFR 1926 [construction industry]; and 29 CFR 1917 [maritime industry]) are legal limits enforceable 

in workplaces covered under the Occupational Safety and Health Act of 1970. NIOSH RELs are 

recommendations based on a critical review of the scientific and technical information available on a 

given hazard and the adequacy of methods to identify and control the hazard. NIOSH RELs can be found 

in the NIOSH Pocket Guide to Chemical Hazards [NIOSH 2005]. NIOSH also recommends different 

types of risk management practices (e.g., engineering controls, safe work practices, employee education/

training, personal protective equipment, and exposure and medical monitoring) to minimize the risk of 

exposure and adverse health effects from these hazards. Other OELs that are commonly used and cited 

in the United States include the TLVs recommended by ACGIH, a professional organization, and the 

WEELs recommended by the American Industrial Hygiene Association, another professional organization. 

The TLVs and WEELs are developed by committee members of these associations from a review of the 

published, peer-reviewed literature. They are not consensus standards. ACGIH TLVs are considered 

voluntary exposure guidelines for use by industrial hygienists and others trained in this discipline “to assist 

in the control of health hazards” [ACGIH 2011]. WEELs have been established for some chemicals “when 

no other legal or authoritative limits exist” [AIHA 2010].
Page 19 Health Hazard Evaluation Report 2008-0245-3127

Appendix B: Occupational Exposure Limits and Health Effects (continued)

Outside the United States, OELs have been established by various agencies and organizations and 

include both legal and recommended limits. The Institut für Arbeitsschutz der Deutschen Gesetzlichen 

Unfallversicherung (IFA, Institute for Occupational Safety and Health of the German Social Accident 

Insurance) maintains a database of international OELs from European Union member states, Canada 

(Québec), Japan, Switzerland, and the United States. The database, available at www.dguv.de/ifa/en/

gestis/limit_values/index.jsp, contains international limits for over 1,500 hazardous substances and is 

updated periodically.

Employers should understand that not all hazardous chemicals have specific OSHA PELs, and for some 

agents the legally enforceable and recommended limits may not reflect current health-based information. 

However, an employer is still required by OSHA to protect its employees from hazards even in the absence 

of a specific OSHA PEL. OSHA requires an employer to furnish employees a place of employment free 

from recognized hazards that cause or are likely to cause death or serious physical harm [Occupational 

Safety and Health Act of 1970 (Public Law 91–596, sec. 5(a)(1))]. Thus, NIOSH investigators encourage 

employers to make use of other OELs when making risk assessments and risk management decisions to 

best protect the health of their employees. NIOSH investigators also encourage the use of the traditional 

hierarchy of controls approach to eliminate or minimize identified workplace hazards. This includes, in 

order of preference, the use of (1) substitution or elimination of the hazardous agent, (2) engineering 

controls (e.g., local exhaust ventilation, process enclosure, dilution ventilation), (3) administrative controls 

(e.g., limiting time of exposure, employee training, work practice changes, medical surveillance), and (4) 

personal protective equipment (e.g., respiratory protection, gloves, eye protection, hearing protection). 

Control banding, a qualitative risk assessment and risk management tool, is a complementary approach 

to protecting employee health that focuses resources on exposure controls by describing how a risk 

needs to be managed. Information on control banding is available at http://www.cdc.gov/niosh/topics/

ctrlbanding/. This approach can be applied in situations where OELs have not been established or can be 

used to supplement the OELs, when available.

Carbon monoxide

CO is a colorless, odorless, tasteless gas produced by incomplete burning of carbon-containing materials. 

The initial symptoms of CO poisoning may include headache, dizziness, drowsiness, or nausea. 

Symptoms may advance to vomiting, loss of consciousness, and collapse if prolonged or high exposures 

are encountered. If the exposure level is high, loss of consciousness may occur without other symptoms. 

Coma or death may occur if high exposures continue [NIOSH 1972, 1977, 1979, 2005; Proctor et al. 1988; 

ACGIH 2001]. The display of symptoms varies widely from individual to individual and may occur sooner 

in susceptible individuals, such as young or aged people, people with preexisting lung or heart disease, or 

those living at high altitudes.
Health Hazard Evaluation Report 2008-0245-3127 Page 20

Exposure to CO limits the ability of the blood to carry oxygen to the tissues by binding with the 

hemoglobin to form COHb. Once exposed, the body compensates for the reduced blood-borne oxygen 

by increasing cardiac output, thereby increasing blood flow to specific oxygen-demanding organs such as 

the brain and heart. This ability may be limited by preexisting heart or lung diseases that inhibit increased 

cardiac output.

Blood has an estimated 210–250 times greater affinity for CO than oxygen, thus the presence of CO in 

the blood can interfere with oxygen uptake and delivery to the body. Once absorbed into the bloodstream, 

the half-time of CO disappearance from blood (referred to as the “half-life”) varies widely by individual 

and circumstance (e.g., removal from exposure, initial COHb concentration, partial pressure of oxygen 

after exposure). Under normal recovery conditions that include breathing ambient air, the half-life can be 

expected to range from 2 to 6.5 hours [WHO 1999]. This means that if the initial COHb level were 10%, 

it could be expected to drop to 5% in 2 or more hours and then to 2.5% in another 2 or more hours. 

If the exposed person is treated with oxygen, as happens in emergency treatment, the half-life time is 

decreased again by as much as 75% (or to as low as approximately 40 minutes). Delivery of oxygen under 

pressure (hyperbaric treatment) reduces the half-life to approximately 20 minutes.

COHb levels vary in persons without occupational exposure to CO. Nonsmokers range from less than 2% 

to 3%; tobacco smokers range from 5% to 20%; and commuters on urban highways can have levels of 5% 

or more [EPA 1991; ACGIH 2001].

Occupational Exposure Criteria

Occupational criteria for CO exposure are applicable to employees who may be at risk of CO poisoning. 

The occupational exposure limits noted below should not be used for interpreting general population 

exposures, because occupational standards are intended for healthy worker populations. The effects of 

CO are more pronounced in a shorter time if the person is physically active, very young, very old, or has 

preexisting health conditions such as lung or heart disease. Persons at extremes of age and persons with 

underlying health conditions may have marked symptoms and may suffer serious complications at lower 

levels of COHb [Kales 1993]. Standards relevant to the general population consider these factors and are 

listed following the evaluation criteria to aid in understanding information presented in the discussion 

section of this report.

Although not directly applicable to the agency 16-hour extended work shift, the NIOSH REL for CO is 35 

ppm for full shift TWA exposure (up to 10 hours) [NIOSH 1992]. The NIOSH REL of 35 ppm is designed 

to protect workers from adverse health effects associated with COHb levels in excess of 5% [NIOSH 1972]. 

NIOSH has established a CO ceiling limit of 200 ppm that should never be exceeded and an IDLH value 

of 1200 ppm [NIOSH 1992, 2000]. An IDLH value is defined as a concentration at which an immediate or 

delayed threat to life exists or that would interfere with an individual’s ability to escape unaided from a space.

Appendix B: Occupational Exposure Limits and Health Effects (continued)
Page 21 Health Hazard Evaluation Report 2008-0245-3127

The ACGIH recommends an 8-hour TWA TLV of 25 ppm based upon limiting shifts in COHb levels 

to less than 3.5%, thus minimizing adverse neurobehavioral effects, such as headache and dizziness, and 

to maintain cardiovascular exercise capacity [ACGIH 2001]. ACGIH also recommends that exposures 

never exceed five times the TLV (thus, never to exceed 125 ppm) [ACGIH 2011]. ACGIH recommends 

a BEI for end-of-shift blood analysis in nonsmoking workers (exposed to CO) of 3.5% COHb [ACGIH 

2011]. The BEI generally indicates a concentration below which nearly all workers should not experience 

adverse health effects. The BEI cannot be applied to current smokers, since smokers have been shown to 

have COHb levels between 4% and 10% [ACGIH 2001; Tomaczewski 2002] and can exceed 15% in heavy 

smokers [Lauwerys and Hoet 2001].

The OSHA PEL for CO is 50 ppm for an 8-hour TWA exposure [29 CFR 1910.1000]. OSHA does not 

currently have a standard for extended work shifts and applies an extended work shift adjustment only to 

full-shift occupational lead exposures [OSHA 1997].

Health Criteria Relevant to the General Public

The EPA has promulgated a NAAQS for CO. This standard requires that ambient air contain no more 

than 9 ppm CO for an 8-hour TWA and 35 ppm for a 1-hour average [EPA 1991]. The NAAQS for 

CO was established to protect “the most sensitive members of the general population” by maintaining 

increases in COHb to less than 2.1%.

The WHO has recommended guideline values and periods of TWA exposures related to CO exposure 

in the general population [WHO 1999]. WHO guidelines are intended to ensure that COHb levels not 

exceed 2.5% when a normal subject engages in light or moderate exercise. Those guidelines are 100 mg/

m3 (87 ppm) for 15 minutes, 60 mg/m3 (52 ppm) for 30 minutes, 30 mg/m3 (26 ppm) for 1 hour, and 10 

mg/m3 (9 ppm) for 8 hours.

References

ACGIH [2001]. Documentation of threshold limit values and biological exposure indices. 7th edition. 

Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [2011]. 2011 TLVs® and BEIs®: threshold limit values for chemical substances and physical 

agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental 

Industrial Hygienists.

AIHA [2010]. AIHA 2010 Emergency response planning guidelines (ERPG) & workplace environmental 

exposure levels (WEEL) handbook. Fairfax, VA: American Industrial Hygiene Association.

Appendix B: Occupational Exposure Limits and Health Effects (continued)
Health Hazard Evaluation Report 2008-0245-3127 Page 22

CFR. Code of Federal Regulations. Washington, DC: U.S. Government Printing Office, Office of the 

Federal Register.

EPA [1991]. Air quality criteria for carbon monoxide. Publication No. EPA-600/8-90/045F. Washington, 

DC: U.S. Environmental Protection Agency.

Kales SN [1993] Carbon monoxide intoxication. American Family Physician 48(6):1100–1104.

Lauwerys RR, Hoet P [2001]. Industrial chemical exposure: guidelines for biological monitoring. 3rd ed. 

Lewis Publishers (CRC Press LLC), Boca Raton, Florida. pp. 474–477.

NIOSH [1972]. Criteria for a recommended standard: occupational exposure to carbon monoxide. 

Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Health Services and Mental Health 

Administration, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 

73-11000.

NIOSH [1977]. Occupational diseases: a guide to their recognition. Rev. ed. Cincinnati, OH: U.S. 

Department of Health, Education, and Welfare, Center for Disease Control, National Institute for 

Occupational Safety and Health, DHEW (NIOSH) Publication No. 77-181.

NIOSH [1979]. A guide to work-relatedness of disease. Rev. ed. Cincinnati, OH: U.S. Department of 

Health, Education, and Welfare, Center for Disease Control, National Institute for Occupational Safety 

and Health, DHEW (NIOSH) Publication No. 79-116.

NIOSH [1992]. Recommendations for occupational safety and health: compendium of policy documents 

and statements. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease 

Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) 

Publication No. 92-100.

NIOSH [2000]. Documentation for immediately dangerous to life or health concentrations. In: NIOSH 

Pocket guide to chemical hazards and other databases. Cincinnati, OH: U.S. Department of Health and 

Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety 

and Health, DHHS (NIOSH) Publication No. 2000-130.

NIOSH [2005]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of Health 

and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational 

Safety and Health, DHHS (NIOSH) Publication No. 2005-149. [http://www.cdc.gov /niosh/npg/]. Date 

accessed: April 2011.

OSHA [1997]. Standard interpretation: calculation methods used under the air contaminants 

standard for extended workshifts. [www.osha.gov/pls/oshaweb/owadisp.show_document? p_

table=INTERPRETATIONS&p_id=22333]. Date accessed: April 2011.

Appendix B: Occupational Exposure Limits and Health Effects (continued)
Page 23 Health Hazard Evaluation Report 2008-0245-3127

Proctor NH, Hughes JP, Fischman ML [1988]. Chemical hazards of the workplace. Philadelphia, PA: J.B. 

Lippincott Company.

Tomaczewski C [2002]. Ch. 97 Carbon Monoxide. In: Goldfrank L, Flomenbaum N, Lewin N, et al., eds. 

Goldfrank’s toxicologic emergencies. 7th ed. New York: McGraw-Hill, pp. 1478–1491.

WHO [1999]. Environmental health criteria 213-carbon monoxide. Second ed. Geneva, Switzerland: 

World Health Organization, ISBN 92 4 157213 2 (NLM classification: QV 662), ISSN 0250-863X.

Appendix B: Occupational Exposure Limits and Health Effects (continued)
Health Hazard Evaluation Report 2008-0245-3127 Page 24

Appendix C: Tables

Table C1. Base camp – personal breathing zone CO concentration averages (ppm) and peaks (ppm) from August 

13–14, 2008.

1st Shift Overnight Partial 2nd shift

ID Job Sample Time 

(military)

CO Avg. 

(Peak) 

Sample Time 

(military)

CO Avg. 

(Peak) 

Sample Time 

(military)

CO Avg. 

(Peak) 

73 Caterer 1201–2100 3.3 (107) 2141–0800 0.12 (37) 0800–1157 0.78 (3.3)

17 Caterer 0627–2105 3.1 (57) 2135–0600 5.7 (> 1000) 0600–1157 2.4 (28)

16 Caterer 0941–2200 1.4 (22) 2200–0600 1.6 (4.6) 0600–1153 3.2 (26)

33 CMD 0749–2300 0.85 (7.1) 2300–0600 1.2 (2.2) 0600–1322 2.6 (74)

31 CMD 0739–2230 1.3 (12) 2230–0630 0.94 (2.9) 0630–1324 1.3 (4.0)

34 COMM 0810–2205 4.2 (> 1000) 0001–0819 1.1 (15) —

53 COMM 0753–2230 1.4 (15) 2230–0600 1.8 (4.2) 0600–1107 2.4 (8.6)

29 Mechanic 0703–2200 5.6 (423) 2200–0600 2.2 (7.3) 0600–1224 3.3 (72)

19 Mechanic 0652–2039 3.9 (> 1000) — 0631–1224 3.0 (29)

35 Medical 0815–2200 2.7 (49) 2200–0600 1.3 (3.9) 0600–1315 1.5 (8.0)

51 Reefer 0535–2100 4.0 (> 1000) 2100–0605 0.24 (22) —

15 Reefer 0535–2013 1.9 (19) — —

74 Reefer 0535–2100 1.8 (15) 2100–0746 0.35 (8.6) —

32 Resource 0749–2200 2.3 (141) 2200–0600 0.57 (5.8) 0600–1208 1.9 (15)

30 Supply/ 

Logistics 0735–2200 1.1 (8.6) 2200–0600 1.4 (5.5) 0600–1238 2.0 (15)

18 Supply 1029–2200 1.5 (45) 2200–0600 2.3 (80) 0600–1345 3.0 (38)

36 Supply 2043–2200 1.2 (5.0) 2200–0600 1.3 (11) 0600–1337 3.2 (128)

37 Supply 0835–2200 0.50 (11) 2200–0600 2.3 (3.5) 0600–1318 2.8 (55)

41 Weed 

Wash — — 0839–1227 5.4 (40)
Page 25 Health Hazard Evaluation Report 2008-0245-3127

Appendix C: Tables (continued)

Table C2. Base camp – general area CO concentration averages (ppm) and peaks (ppm) from August 13–14, 2008.

Location Sample Time 

(military)*

CO Avg. 

(Peak) 

Begin–2200

CO Avg. 

(Peak) 2200–

0500

CO Avg. 

(Peak) 

0500–End

CO Avg. 

(Peak) 

Overall

RAE Systems AreaRAE monitors

North Camp Area 0546–1231 0.52 (2.9) 0.01 (0.80) 0.78 (3.3) 0.48 (3.3)

Security Area (South) 0558–1231 0.24 (3.8) 0.01 (0.20) 0.21 (2.2) 0.18 (3.8)

East Camp Area 0546–0807† 0.49 (16) 0.07 (20) 0.0 (0.0) 0.34 (20)

Operations Center Area (West) 0558–1231 1.2 (3.6) 0.51 (1.8) 1.5 (3.5) 1.1 (3.6)

Shower and Kitchen 

(Middle of Camp)

0558–1231 0.02 (1.0) 0.0 (0.20) 0.03 (0.30) 0.02 (1.0)

ToxiUltra Atmospheric Monitors

Agency Representatives Tent 0754–1430 2.0 (5.0) 0.0 (1.0) 2.0 (5.0) 1.0 (5.0)

Mobile Mapping Service Trailer 0745–1209 1.8 (13) 0.71 (2.9) 1.0 (2.3) 1.3 (13)

Logistics Trailer 0747–1210 2.2 (7.8) 2.9 (5.2) 3.4 (10) 2.7 (10)

Food Trailer 0750–1213 1.3 (8.6) 3.8 (52) 2.7 (9.5) 2.3 (52)

Sleeping Trailer 1912–0830‡ 2.5 (4.0) 2.2 (3.0) 2.4 (3.7) 2.3 (4.0)

Laundry Trailer 0805–1215 1.2 (3.7) 2.7 (4.0) 3.6 (6.1) 2.2 (6.1)

Communication Unit Tent 0803–1208 0.51 (2.1) 0.95 (1.9) 1.6 (3.1) 1.6 (3.1)

Facilities Tent 0816–1207 1.2 (14) 1.2 (1.8) 1.8 (8.8) 1.4 (14)

* = Time begins on August 13, 2008, and ends on August 14, 2008.

† = Memory card full. No additional data collected after 0807 on August 14, 2008.

‡ = Only collected data during the overnight period while occupied by base camp personnel.
Health Hazard Evaluation Report 2008-0245-3127 Page 26

Appendix D: Figures

Figure D1. Caterer (ID 17) real-time CO concentrations on August 13–14, 2008, at 

the base camp.

Figure D2. COMM (ID 34) real-time CO concentrations on August 13–14, 2008, at the 

base camp.
Page 27 Health Hazard Evaluation Report 2008-0245-3127

Appendix D: Figures (continued)

Figure D3. Mechanic (ID 29) real-time CO concentrations on August 13–14, 2008, at 

the base camp.

Figure D4. Mechanic (ID 19) real-time CO concentrations on August 13–14, 2008, at 

the base camp.
Health Hazard Evaluation Report 2008-0245-3127 Page 28

Appendix D: Figures (continued)

Figure D5. Reefer (ID 51) real-time CO concentrations on August 13–14, 2008, at the 

base camp.

Figure D6. Resources (ID 32) real-time CO concentrations on August 13–14, 2008, at 

the base camp.
Page 29 Health Hazard Evaluation Report 2008-0245-3127

Appendix D: Figures (continued)

Figure D7. Supply (ID 36) real-time CO concentrations on August 13–14, 2008, at the 

base camp.
Health Hazard Evaluation Report 2008-0245-3127 Page 30

Acknowledgments and

 Availability of Report

The Hazard Evaluations and Technical Assistance Branch (HETAB) of the National Institute for 

Occupational Safety and Health (NIOSH) conducts field investigations of possible health hazards in the 

workplace. These investigations are conducted under the authority of Section 20(a)(6) of the Occupational 

Safety and Health Act of 1970, 29 U.S.C. 669(a)(6), which authorizes the Secretary of Health and Human 

Services, following a written request from any employer or authorized representative of employees, to 

determine whether any substance normally found in the place of employment has potentially toxic effects 

in such concentrations as used or found. HETAB also provides, upon request, technical and consultative 

assistance to federal, state, and local agencies; labor; industry; and other groups or individuals to control 

occupational health hazards and to prevent related trauma and disease.

The findings and conclusions in this report are those of the authors and do not necessarily represent 

the views of NIOSH. Mention of any company or product does not constitute endorsement by NIOSH. 

In addition, citations to websites external to NIOSH do not constitute NIOSH endorsement of the 

sponsoring organizations or their programs or products. Furthermore, NIOSH is not responsible for 

the content of these websites. All Web addresses referenced in this document were accessible as of the 

publication date.

This report was prepared by Robert E. McCleery, Anthony Almazan, and Chad H. Dowell of HETAB, 

Division of Surveillance, Hazard Evaluations and Field Studies, and John Snawder of the Biomonitoring 

and Health Assessment Branch, Division of Applied Research and Technology. Medical field assistance 

and support was provided by Elena Page and Bruce Bernard. Technical support was provided by Dino 

Mattorano of the U.S. Environmental Protection Agency. Health communication assistance was provided 

by Stefanie Evans. Editorial assistance was provided by Cathy Rotunda. Desktop publishing was performed 

by Greg Hartle.

Copies of this report have been sent to employee and management representatives at the federal agency, 

the state health department, and the Occupational Safety and Health Administration Regional Office. 

This report is not copyrighted and may be freely reproduced. The report may be viewed and printed at 

http://www.cdc.gov/niosh/hhe/. Copies may be purchased from the National Technical Information 

Service (NTIS) at 5825 Port Royal Road, Springfield, Virginia 22161.
Page 31 Health Hazard Evaluation Report 2008-0245-3127

This page left intentionally blank.
Health Hazard Evaluation Report 2008-0245-3127 Page 32

This page left intentionally blank.
Below is a recommended citation for this report:

NIOSH [2011]. Health hazard evaluation report: determining base camp personnel 

exposures to carbon monoxide during wildland fire suppression activities – 

California. By McCleery R, Almazan A, Dowell C, Snawder J. Cincinnati, OH: U.S. 

Department of Health and Human Services, Centers for Disease Control and 

Prevention, National Institute for Occupational Safety and Health, NIOSH HETA 

No. 2008-0245-3127.

To receive NIOSH documents or information about 

occupational safety and health topics, contact NIOSH at:

1-800-CDC-INFO (1-800-232-4636)

TTY: 1-888-232-6348

E-mail: cdcinfo@cdc.gov

or visit the NIOSH web site at: www.cdc.gov/niosh.

For a monthly update on news at NIOSH, subscribe to 

NIOSH eNews by visiting www.cdc.gov/niosh/eNews.

Delivering on the Nation’s promise:

Safety and health at work for all people

through research and prevention.

 National Institute for Occupational 

Safety and Health