VW<&gi Reference

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Ur Quality Criteria for Storage

r’aper-Based Archival Records

November 1983

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Prepared for: Public Buildings Service

General Services Administration

National Capitol Region

Washington, D.C. 20407

National Archives and Records Service

QC Washington, D.C. 20408

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33-2795

1333

NBSIR 83-2795

AIR QUALITY CRITERIA FOR STORAGE OF

PAPER-BASED ARCHIVAL RECORDS

Robert G. Mathey, Thomas K. Faison, Samuel Silberstein

Center for Building Technology

National Engineering Laboratory

U S. Department of Commerce

National Bureau of Standards Washington, D C. 20234

James E. Woods

Consultant, Ames, Iowa

Warren B. Johnson

Consultant, Dallas, Texas

William P. Lull Consultant, New York, New York

Charles A. Madson

Consultant, River Forest, llinois Amos Turk

Professor, Department of Chemistry

The City College of the City

University of New York; New York, New York 10031

Karl L. Westlin

Consultant, Louisville, Kentucky

Paul N. Banks

Consultant, New York, New York

NATIONAL au.\ ... j OF STANDARDS

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November 1983

Prepared for: Public Buildings Service

General Services Administration

National Capitol Region

Washington, D.C. 20407

National Archives and Records Service

Washington, D.C. 20408

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
*

4
ABSTRACT

Criteria for temperature, relative humidity, and gaseous and particulate

contaminant concentrations are proposed for spaces used for storage and preservation of paper-based archival records. The criteria are based on available

information from the literature, and recommendations of the January 19-20, 1983,

National Bureau of Standards Workshop on Environmental Conditions for Archival

Storage. Methods are discussed for meeting these criteria. Air quality criteria are proposed for different categories of archival storage. Factors to

consider in the design of archival storage facilities are addressed and recom- mendations made to aid in the design of environmental conditioning systems for

these facilities. A review of literature describes the damage that may be

caused by high temperature, high and low relative humidity, and air pollutants

to paper-based records.

Results of measurements of temperature, relative humidity, air exchange rate,

and gaseous contaminant concentrations (sulfur dioxide, nitrogen oxides, and

ozone) in the National Archives Building in Washington, D.C., are presented.

These measurements are compared with those made in other buildings having

controlled environments.

Key words: air quality, archival storage, criteria, design parameters,

environmental conditioning systems, environmental conditions,

environmental control, preservation.

iii
PREFACE AND ACKNOWLEDGMENTS

This study on air quality criteria for storage of paper-based archival records

was conducted by the Building Materials Division and the Building Equipment

Division of the Center for Building Technology, National Engineering Laboratory,

National Bureau of Standards (NBS) . The work was sponsored by the Public

Buildings Service (PBS) of the General Services Administration (GSA) and the

National Archives and Records Service (NARS) because of the need to upgrade

the performance of the heating, ventilating, and air-conditioning systems at

the National Archives Building. This document provides criteria and documentation for temperature, relative humidity, and air pollutant concentrations in

spaces used for storage of paper-based archival records. It is based on available information on the preservation of paper-based materials and the

capabilities of commercially- available environmental conditioning systems.

Information used in the preparation of this report was obtained from several

sources: (a) a report entitled, "Final Report on January 19-20, 1983 NBS

Workshop: Environmental Control for Archival Record Storage", NBS-GCR-83-438

August 1983, by Warren B. Johnson, William P. Lull, Charles A. Madson, Amos Turk,

Karl L. Westlin, James E. Woods, and Paul N. Banks; (b) a report entitled,

"Measurement of the Concentration of Sulfur Dioxide, Nitrogen Oxides, and Ozone

in the National Archives Building," by E. E. Hughes and R. Myers, NBSIR 83-2767,

November 1983 (appendix B) ; (c) a report entitled, "Air Exchange Rate Measurements in the National Archives Building," by Samuel Silberstein, Richard A. Grot,

Douglas 0. Pruitt, Philip Engers, Patrick J. Lane, and Steven E. Schweinfurth,

NBSIR 83-2770, August 1983 (appendix C) ; (d) a letter report entitled, "Factors

Affecting the Deterioration of Paper-Based Archival Records—A Literature

Search," by Samuel Silberstein, May 1983; (e) measurements of temperature and

relative humidity taken by GSA and NARS; and (f) other information from the

literature.

The contributions of the Workshop participants who reviewed the Workshop

Report, Alan R. Calmes, Tim Padfield, Carl J. Wessel, and William K. Wilson,

are appreciated. The Word Processing Center of the Center for Building

Technology is gratefully acknowledged for typing this report.

iv
TABLE OF CONTENTS

Page

ABSTRACT iii

PREFACE AND ACKNOWLEDGMENTS iv

1. INTRODUCTION 1 1 . 1 Background . 1 1.2 Objectives 1 1.3 Scope of the Project 2

2. NATURE OF PROBLEM 3

2.1 Paper-Based Records 3

2.2 Factors Affecting the Deterioration of Paper-Based Records . 4

2.2.1 Separate Storage Areas 4

2.2.2 Ventilation 4

2.2.3 Temperature (Dry- Bulb) 5 2. 2. 3.1 Damage Caused by High Temperature 5 2. 2. 3.

Examples of Suggested Temperature Limits ... 6

2.2.4 Relative Humidity 6

2. 2. 4.1 Damage Caused by High Relative Humidity .... 6

2. 2. 4.

Examples of Suggested Relative Humidity

Limits 7 2.2.5 Gaseous Air Pollutants 8

2. 2. 5.1 Damage Caused by Gaseous Air Pollutants .... 8

2. 2. 5.

Examples of Suggested Gaseous Pollutant

Concentration Limits 9

2.2.6 Particulates 9

2. 2. 6.1 Damage Caused by Particulates 9

2. 2. 6.

Examples of Suggested Particulate

Concentration Limits 10

2.2.7 Biological Agents 10

2.2.8 Examples of Design Criteria 11

2.3 Sources of Contaminants 12

2.3.1 Building Materials 12

2.3.2 Paper-Based Materials 13

2.3.3 Human Activity 13

2.3.4 HVAC Systems 13

2.3.5 Interactions of Contaminants 14

2.4 Workshop on Environmental Conditions for Archival Records

Storage 14

3. DESIGN PARAMETERS 15

3.1 Expected Outdoor Level of Contaminants 15

3.2 Preservation and Conservation Factors 16

3.3 Human Factors 16

3.4 Architectural Factors 18

3.5 Economic Factors 19

3.6 Recommended Air Quality Criteria for Archival Storage 21

v
TABLE OF CONTENTS

Page

4. AIR QUALITY CONTROL 23

4.1 Steady-State Model for Air Quality Control 23

4.2 Components and Systems 24

4.2.1 Temperature and Relative Humidity Control 24

4.2.2 Control of Gaseous Contaminants 26

4. 2. 2.1 Granular Beds . . . . 26

4. 2. 2. 2 Wet Scrubbers 27

4.2.3 Control of Particulate Contaminants 29

4.2.4 Integrative Control 30

5. PERFORMANCE EVALUATION OF ENVIRONMENTAL CONDITIONING SYSTEMS .... 32

5.1 Monitoring Procedures 32

5.1.1 System Performance 32

5.1.2 Component Performance 33

5.2 Assessment Procedures 34

5.2.1 System Performance 35

5.2.2 Component Performance 35

5.3 Evaluation Procedure 35

6. BASELINE DATA FOR SELECTED FACILITIES USED FOR STORAGE OF

PAPER-BASED MATERIALS 36

6.1 Facility and Type of Environmental Condition System ........ 36

6.1.1 National Archives Building 36

6.1.2 Madison Building of the Library of Congress 36

6.1.3 East Wing of the National Gallery of Art 37

6.2 Measurements and Data Analyzed by NBS 37

6.2.1 Sulfur Dioxide, Nitrogen Oxides, Ozone, Temperature,

and Relative Humidity 37

6.2.2 Air Exchange Rate Measurements in the National

Archives Building 39

6.2.3 Analysis of Temperature and Humidity Data Recorded

by the National Archives and Records Service

and the General Services Administration 40

7. SUMMARY 43

8. REFERENCES 45

APPENDIX A. LIST OF WORKSHOP PARTICIPANTS A-l

APPENDIX B. MEASUREMENT OF THE CONCENTRATIONS OF SULFUR DIOXIDE,

NITROGEN OXIDES, AND OZONE IN THE NATIONAL ARCHIVES

BUILDING B-l

APPENDIX C. AIR EXCHANGE RATE MEASUREMENTS IN THE NATIONAL ARCHIVES

BUILDING C-l

vi
LIST OF TABLES

Page

Table 1. Summary of Outdoor Air Contaminants and Concentrations

Given in National Ambient Air Quality Standards 17

Table 2. Summary of Outdoor Air Thermal Design Conditions for the

Washington, D.C. Area, (Washington National Airport) from

1981 ASHRAE Fundamentals Handbook [ 68 ] 17

Table 3. Recommended Air Quality Criteria for Archival Storage 22

Table 4. Relationship between Residence Time, n, of a Gaseous

Molecule in a Granular Bed and the Contact Efficiency,

e, of the Bed 27

Table 5. Summary of Actions of Activated Alumina (AI 2 O3 ) 28

Table 6 . Summary of Actions of Activated Carbon 28

Table 7. Estimated 1983 Costs of Installing and Operating Various

Particulate Control Devices 31

Table 8 . Temperature and Relative Humidity Data 41

LIST OF FIGURES

Figure 1. One-compartment, uniformly-mixed, steady-state model

for indoor air quality control 24

vii
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1. INTRODUCTION

1.1 BACKGROUND

The National Archives Building in Washington, D.C., which houses many of the

Nation’s records intended for permanent preservation, was constructed in the

early 1930 's. It was one of the first buildings in Washington, D.C. , to provide

all season environmental control. The controlled environment was prescribed in

order to protect the Nation's valuable records from the effects of extreme temperature, high and low relative humidity excursions, and attack from acid gases

such as those resulting from sulfur dioxide. The original heating, ventilating, and air conditioning system was designed to meet these objectives, but has

since been modified a number of times and has had a history of less than

satisfactory performance [1]J/ .

A recent report [1] from the General Services Administration, Office of the

Inspector General recommended the following actions to improve environmental

conditions at the National Archives Building:

a. Performance testing should be conducted to determine if environmental

conditions (temperature and relative humidity fluctuations, and gaseous and particulate pollutant levels) exist in the building which

would subject valuable records and documents to immediate irreparable

damage.

b. Standards for environmental conditions should be adopted which would

protect the records from accelerated deterioration.

c. The Public Buildings Service should develop cost estimates for

bringing the control of the environmental conditions (temperature,

relative humidity, gaseous and particulate pollutant concentrations)

into compliance with the adopted standards.

d. These actions should be carried out as part of a time-phased plan to

upgrade the performance of the heating, ventilating, and airconditoning systems.

1.2 OBJECTIVES

To aid in carrying out the recommendations (section 1.1), to improve the

performance of the heating, ventilating, and air-conditioning systems at the

National Archives Building, the Public Buildings Service of the General Services Administration requested the National Bureau of Standards’ Center for

Building Technology to provide criteria for environmental conditions for the

storage and preservation of paper-based archival records. This study may also

be useful in the design and modification of other archival storage facilities.

Figures in brackets refer to literature references given in section 8
The objectives of the report are to provide criteria which establish limits for

control of environmental conditions in spaces used for storage of paper-based

archival records; to consider factors affecting the degradation of paper and

books which can be used to document the rationale for selecting specific criteria; to include information to assist in the design of environmental conditioning systems with regard to preservation of stored paper-based materials; to

review up-to-date standards and operating procedures used in the design and

maintenance of records storage facilities; and to present the results of mea- surements of pollutants, air exchange rates due to infiltration, temperatures

and relative humidities in the stack areas of the National Archives Building

which were used to determine baseline performance of the existing environmental

control system. Gaseous pollutant levels in this building were compared to the

pollutant levels in other buildings with similar functions having rigid

environmental limits.

1 .3 SCOPE OF THE PROJECT

This report is concerned only with the control of environmental conditions in

storage facilities for paper-based archival records, and not with other areas

of buildings. Excluded from consideration are general reading rooms, exhibition

areas, offices, and work areas except as they influence storage areas. Also

excluded from consideration are photographic materials (photographs, microfilms,

and negatives, for example), parchments, and vellums. These may comprise significant parts of many collections and must be considered in designing airconditioning systems. Light is not addressed in this report, although it may

be as important in causing deterioration as other factors.

Much of the information and data presented in this report were obtained from

existing sources including the literature, and opinions of those knowledgeable

in preservation and conservation of paper-based materials and in the capabilities of environmental conditioning components and systems. No laboratory

research on the preservation of paper-based materials was performed during the course of the study. Measurements were made of temperature, relative humidity,

air infiltration rate, and gaseous pollutants (sulfur dioxide, nitrogen oxides,

and ozone) in several locations in the storage areas of the National Archives

Building to determine baseline performance of the existing environmental control system (appendices B and C) . For comparison, measurements (except for air

infiltration rate) were also made in the Madison Building of the Library of

Congress and the East Wing of the National Gallery of Art. These buildings

have modern environmental conditioning systems designed to maintain rigid

environmental limits.

Criteria were provided in two ways: 1) through a literature search, and 2) by

a Workshop on Environmental Conditions for Archival Records Storage held at the

National Bureau of Standards on January 19-20, 1983 [2], In addition to providing criteria, the Workshop participants reviewed equipment and other means for

meeting these criteria. Workshop participants are listed in appendix A.

2
2. NATURE OF THE PROBLEM

The National Archives contains some 3,000,000,000 paper-based records in the

form of loose documents, bound volumes, maps, manuscripts, and many other forms.

As a general rule, it is assumed that once an item has been accessioned into

the Archives (on the basis of legal requirements or historical value) it is to

be retained indefinitely.

However, the assumption of "permanent retention" has caused at least two major

problems: preservation of the records and space for housing them. For an estimated 17 percent of the records which have unquestioned "intrinsic value,” preservation of the original records for as long as possible (in other words,

indefinitely) is the single goal [2].

For the other 83 percent, however, it has recently been decided that they can probably be preserved by microfilming or converting them to some other secondary medium and discarding the originals. This has obvious benefits for space

conservation, and significant cost advantages over preservation of the original

documents. However, it is estimated that at present rates of mircofilm production, it would take about 435 years to convert just those documents that are most in need of conversion [2]. In other words, even with the most efficient

technology now available, it will not be possible to capture the intellectural

content of the documents before they have deteriorated to the point that they

can no longer be handled.

Optimum storage conditions for paper-based records are essential. Important

factors in designing these conditions include storage location, storage duration, frequency of access, contaminants, thermal loads, system constraints,

and economics.

2.1 PAPER- BASED RECORDS

Although there are many exceptions and variations, the types of records under

consideration usually consist of writing, typewriting, copying, or printing ink

(of one or more colors) on paper. Additionally, some documents are bound, which

implies composite structures; that is, objects of some degree of structural

complexity composed of a variety of different materials; for example, thread,

adhesives, cardboard, cloth, leather. Books are composed not only of different

types of papers, but also of inks, glues, and bindings. All these materials

must be protected simultaneously. Care of books and documents, their composition, the factors damaging to them, and recommendations for their storage and

preservation have been described by Wilson and Gear [3].

Paper itself is a highly variable material containing cellulose fibers of

natural origin. While some early (and incidentally highly stable) papers con- sist almost wholly of highly pure cellulose fibers, modern papers may contain

lignin from wood, and additives such as alum-rosin sizing. Thus, different

papers have different degrees of inherent stability, and different rates of

deterioration.

3
2.2 FACTORS AFFECTING THE DETERIORATION OF PAPER- BASED ARCHIVAL RECORDS

The factors considered as those affecting the deterioration of paper-based

archival records include temperature, relative humidity, gaseous and particulate contaminants, ventilation, biological agents, and lighting. The effects

of lighting on paper-based records have not been covered in this report.

Lighting systems can be designed and used to satisfy both preservation and

visibility requirements [4]

.

The four environmental conditions generally

accepted as those that primarily affect paper-based archival records are temperature, relative humidity, gaseous and particulate contaminants [5].

This section of the report is concerned with factors that affect deterioration

of certain paper-based archival records, mainly books, that can be controlled

by air conditioning systems. A compilation of descriptions of current practice

and recommendations from several sources are given which provides information

on factors to be considered in the design of spaces for storage and use of

paper-based archival records. The information presented in this section is

not meant to be an exhaustive listing of all references dealing with paper

preservation, but it is intended to cite and summarize several representative

sources that describe current practice in paper-record preservation. Examples

are given of guidelines on temperature, relative humidity, pollutant

concentrations, and protection against biological agents.

2.2.1 Separate Storage Areas

A general point in paper preservation is that optimal conditions, especially

temperature, are not the same as conditions whose primary purpose is human

comfort [6]. For this and other general protective and security reasons,

archival materials should be stored in special storage areas and removed to

other areas for use [7]. One of the reasons is that people can bring dust,

insects, spores and food particles containing nutrients for insects and vermin

into storage areas [8]

.

Storage areas may be maintained at slightly positive pressure with respect to

surrounding areas to prevent infiltration of untreated air [2].

2.2.2 Ventilation

Ventilation must be adequate to prevent stagnant air and the formation of

microclimates around books that are at variance with standards for air pollutants, temperature, and humidity [7]. Adequate ventilation around all storage

materials is also required to remove any pollutants that are emitted by the

materials themselves or fixtures near them [9]

.

The Royal Ontario Museum is an example of a building that was recently expanded

and refurbished with preservation of its collections as a main objective.

Separate air conditioning systems were installed so that different conditions

could be maintained for different collections. Minimum airflow rates were

established, depending on the size of the space served, from 60 L/h (2.1 ft-fyh)

for spaces having a volume of 0.3 m^ (11 ft^) (display cases), to 1300 L/h

(46 ft-Vh) for spaces having a volume of 30 (1060 f t^) . Each gallery was

4
fitted with a system so that it could be separately fumigated. The fumigant

is exhausted through pipes separate from the air-handling system [10].

2.2.3 Temperature (Dry-Bulb)£/

2. 2. 3.1 Damage Caused by High Temperature

Heat, either by itself or in combination with light and/or insufficent or excessive moisture, damages paper and other materials used in records. The

deterioration of paper becomes more rapid as the temperature is increased [11].

With an increase and decrease in temperature, paper-based materials alternately

expand and contract, and may ultimately crack. Expansion and contraction of

paper-based materials is, in general, more pronounced with increases and

decreases in relative humidity. Heat causes water, solvents, and plasticizers

to be driven off. Heat also increases the reaction rate of pollutants with

books, changes acidity, and promotes mildew growth. As a result, paper is

embrittled, yellowed, and weakened as measured in tear, burst and tensile tests

[8,12]. Barrow’s measurements [13] showed that for each temperature drop of

20°C (36°F), it takes 7.5 times as long to reduce to the same extent the folding endurance of paper, a measure of its ability to withstand use. It should

be noted that exposure of some types of paper to heat even for short periods

causes yellowing and embrittlement. Other types of paper, those compounded

for stability, can be heated for a long time without observable change.

In general, low temperatures preserve paper, provided that relative humidity

is maintained at proper levels. Moisture content in equilibrium with 30 percent relative humidity is as low as is safe for paper [8] . A sudden drop in

temperature increases relative humidity, and may result in condensation and

consequent damage [8]

It has been assumed, although not demonstrated, that materials for which maximum

longevity is required, freezing would dramatically prolong their life [2]. The

effects of freezing temperatures on paper-based materials have not been fully

studied.

Paper is not uniformly sensitive to heat and other deteriorative factors. Rag

papers were not affected by heat in tests performed by Shaw and O'Leary [14].

Purified wood pulp was fairly stable, and a mixture of sulfite and soda pulp

was less stable than purer fibers. There is a close relationship between the

purity of cellulosic fibers and stability of unsized papers made from them,

when only a small amount of alum and no rosin size is used. In other tests,

acidity of paper affected the ability to withstand heat [8]

Smith [15] used Browning and Wink's [16] Arrhenius equation approach to

calculate relative lifetimes of papers at various temperatures. This approach

is based on the fact that the rate of chemical reactions, including hydrolysis

]J Dry-bulb temperature is defined as the temperature of the air as measured

by an accurate thermometer. Exposures to mean radiant temperatures or other infra-red radiation are not addressed in this report.

5
of cellulose, increases with increased temperature according to the Arrhenius

equation. Luner [17] pointed out difficulties with this approach, including

its dependence on the characteristics of papers. Smith [15] also predicted the

combined effects of temperature and acidity. The interested reader is referred

to the original references for more details.

2. 2. 3. 2 Examples of Suggested Temperature Limits

Banks recommends the lowest possible temperature for book storage [7]. However,

he allows for limitations to low temperature. People can not be entirely separated from books. Even if separation were possible, there is a lower temperature limit that would be tolerated by employees. Too great a temperature

difference between storage and use areas could result in condensation damage

when books are brought from the former to the latter. If reading rooms were maintained at a maximum temperature of 24. 5° C (76°F) and a maximum relative

humidity of 50 percent, then no condensation would result if the temperature were lowered to 14°C (57 °F). Storage and use of materials should ideally be

kept at as nearly the same temperature as possible. However, in libraries in

which most materials are used infrequently, if at all, it is advantageous, in

practice, to keep storage areas cooler than use areas [7]. Thus, in this case,

the design criterion for temperature should be as low as consistent with such

other considerations as the need for human access to storage areas [2].

The Library of Congress maintained use areas at 24° C (75° F) and storage areas

at 20°C (68°F) in 1974. Storage temperatures are not lower than 20°C (68°F)

because they must accommodate both books and people [7]. The British Museum

Library maintains closed access rooms at 13-18°C (55-65°F) and other rooms at

18-21°C (65-70°F) [7]. The Royal Ontario Museum maintains different sets of

conditions for different parts of its collections. Its rare books and leather

bookbindings are stored at 21-23. 5°C (74°F) [10]. Banks [7] recommends book

storage at 15.5°C (60°F) plus or minus 3°C (5°F). Darling and Webster [18]

recommend that temperatures should be kept at 18°C (65°F) plus or minus 3°C

(5°F) year-round in collections subject to regular use. Storage collections

should be maintained at lower temperatures. The Canadian Conservation Institute

[19] recommends an optimum temperature of 21°C (70°F) with a daily fluctuation

of no more than 1.5°C (3°F). The maximum acceptable temperature is between

20°C (68°F) and 25°C (77°F) with a monthly permissible changeover of 5°C (9°F).

This is based on human comfort; to prevent deterioration, even lower

temperatures would be tolerable.

2.2.4 Relative Humidity

2. 2. 4.1 Damage Caused by High Relative Humidity

Relative humidity is another important factor in deterioration of paper in

libraries. Paper and virtually all other materials used in records absorb

moisture and their moisture content has profound effects of them. Water content of materials such as paper varies directly with the relative humidity of

the surrounding atmosphere because there is an equilibrium between water in

these materials and in air. Since paper-based materials expand with increasing

moisture content, it is important that relative humidity be controlled within

6
narrow limits. In an accelerated aging study it was clearly demonstrated that

moisture has a profound effect on the degradation rate of paper, particularly

at high temperatures [20]. Relative humidity is the ratio of the actual amount

of water vapor present in air to the amount of water vapor present at saturation for the same temperature and pressure. As temperature increases, so does

the water vapor capacity of air. Both excessive and insufficient moisture

contents, and hence high and low relative humidities at temperatures normally

encountered in libraries, can damage books [7]. (The reader is referred to

[21] for a thorough treatment of the relationship between water content and

relative humidity.) This is why there is currently no agreement in the literature on an optimum relative humidity level for storage of paper-based materials

[7].

High relative humidity increases the rate of deteriorative chemical reactions

[7]. Movement of moisture in books in response to fluctuations in relative

humidity may carry deteriorative contaminants such as acids and helps to distribute them throughout the book. At high levels of relative humidity some dyes

and adhesives may dissolve out of books and other paper-based materials. Accumulation of moisture and hydration may turn paper to pulp and cause pages to

stick together. Excessive moisture also leads to biological attack by fungi,

resulting in staining of paper and leather, and weakening of materials [8].

This can occur at relative humidities above about 65 percent [22-24]. While

low relative humidity by no means eliminates or eradicates insect infestations,

high levels encourage them. Bacteria are not of concern unless the relative

humidity is greater than about 70 percent and the temperature is above about

24°C (75°F)

Leather at 40°C (104°F) and 100 percent relative humidity loses all its strength

[25]. Water in paper in equilibrium with 50 percent relative humidity hastens

the rate of deterioration during laboratory tests in which accelerated aging

is artifically induced [16]. On the other hand, insufficient moisture leads

to drying, brittleness and disintegration [7,20]. Natural adhesives are especially subject to desiccation and embrittlement [7,26].

Folding endurance has been shown to be dependent on control of relative humidity

[8,27]. Up to a point in some cases, each 10 percent rise in relative humidity

results in doubling of folding strength of paper [28]

Flexibility of paper

can increase two or three times with a change in relative humidity from 30 to

50 percent [29]. Thus, relative humidity can have a considerable effect on the use of books and documents which consists of weak or embrittled paper. Other

materials such as leather and animal glues show similar effects.

2. 2. 4.Examples of Suggested Relative Humidity Limits

Unlike other factors, there is no agreement on what constitutes an optimum

relative humidity level for preservation of books. At temperatures normally

found in libraries, relative humidities are generally recommended to be, and are generally maintained at some point in the range of 30 to 65 percent, most

often near 50 percent [7,8,10,18,19,30,31]. Fluctuations in relative humidity

may be damaging [7]. Diurnal excursions from the set point are recommended to

be within 2 to 6 percent by different sources, some of whom are willing to

7
permit greater variations over longer periods [7,10,17,19]. For example,

Banks [7] states that cycling at infrequent intervals is less damaging if the

total range is less than 12 percent. The Canadian Conservation Institute [19]

standard permits a minimum acceptable relative humidity of 38 percent for

winter and 55 percent for summer with a maximum set-point changeover rate of 5 percent per month. The Royal Ontario Museum points out that the changeover to

a new relative humidity after a new air-conditioning system has been installed

should be very slow [10]. To maintain high relative humidity during winter,

the Canadian Conservation Institute recommends that the building be maintained

at slightly negative pressure relative to outdoors whenever pollution levels

permit. Condensation damage has been reported to occur in air-cooled buildings

[8,30]

As stated above, there is insufficient information to recommend an optimum

relative humidity. Recommendations for relative humidities of less than 50 percent are based on laboratory studies of paper aging, not on studies of actual

use of books in libraries [7]. On the other hand, according to Smith [15]

recommendations for relative humidity of 50 percent emphasize current physical

properties at the expense of future properties. In this vein, Banks [32] recom- mends that air-handling systems be capable of being modified to achieve lower

relative humidities as further research might suggest this to be desirable.

2.2.5 Gaseous Air Pollutants

2. 2. 5.1 Damage Caused by Gaseous Air Pollutants

Gaseous air pollutants damage books by making them acidic, which promotes

degradation by hydrolysis, and by oxidation, which causes discoloration and

disintegration, and by providing essential nutrients for fungal growth, which

itself is damaging to books [8,33]. Paradoxically, both oxidants such as ozone

and reducing agents such as sulfur dioxide, can coexist in the atmosphere

because of their extreme dilution [34]. The chemical pollutants of greatest

concern are sulfur dioxide, the oxides of nitrogen, and ozone.

Acidity, an indisputable cause of book deterioration [8,15], results mostly

from the processes used to manufacture paper and from leather tanning, in the case of leather-bound books. Inks may make paper acidic. Acids are produced

from oxides of sulfur and nitrogen, which are universally found air pollutants

[8,15,35-38]. Wood has been reported to emit carboxylic acids, especially

acetic acid, and also aldehydes and alcohols [9]; this may or may not be true

of paper as well. Library materials, for example shelves, may be made of wood.

At concentrations found in normal city atmospheres, sulfur dioxide is readily

absorbed at the edges and by exposed pages and areas of a book [8,37,39-41].

Extensive studies have demonstrated that both paper and leather avidly absorb

SO 2 [29,39,42]. These studies have included comparisons of identical books

that have been stored in areas having different atmospheric SC>2 levels, and

studies of the difference of pH levels between the edges and the centers of

books. By itself, SO2 is not damaging to books. However, once absorbed, its

oxidation to sulfur trioxide is catalyzed by metallic impurities in paper [8,

35,43,44] and by leather surfaces. Oxidation may result from reaction with

8
nitrogen dioxide, ozone, peroxides, and peroxy free radicals. Some of these

reactions may possibly be catalyzed by inorganic constituents in the paper.

Upon combination with water, sulfur trioxide yields sulfuric acid. Similarily,

nitric acid is produced from oxides of nitrogen. Sulfuric and nitric acids

then hydrolyze cellulose, causing decreased tear resistance and flexibility

(folding endurance) and ultimately disintegration of paper [8,15].

Hydrolysis induced by sulfuric acid is also the prime cause of leather

deterioration [8,37,45,46]. Below pH 3, leather becomes dry, reddish-brown and

porous. It peels or powders, is easily scratched, its corners wear easily and

cracks appear. This syndrome is known as "red rot." The ideal protection for

leather bookbindings is isolation from contamination by sulfuric acid and

storage in air-conditioned areas [37].

Oxidants, another class of damaging gaseous pollutants, include ozone and

nitrogen dioxide. These pollutants, as mentioned above, help oxidize sulfur

dioxide to sulfur trioxide. Oxidation discolors paper. Nitrogen dioxide

reacts with polymeric materials such as rubber, synthetic elastomers used as fabrics, threads, and adhesives [ 8 ]. Little information was found in the literature on the effects of N0X and O 3 on paper-based archival records, but they are also assumed to be harmful. The effect of ozone was studied by Bogoty, Campbell

and Appel [47]. They reported that cotton textiles deteriorated somewhat when

wet, but deterioration was slight in comparison with other elements of weathering, such as light, heat, and wetting and drying. No noticeable change occurred

during dry exposure to ozone.

2. 2. 5.Examples of Suggested Gaseous Pollutant Concentration Limits

As an ideal, the British Museum Library recomends that sulfur dioxide, nitrogen

oxides, ozone and dust be entirely removed [7,15,33]. The Royal Ontario Museum

requires charcoal or equivalent filtration to remove sulfur dioxide, ozone and

nitrogen oxides [10]. Banks suggests concentration limits of 4 ppb sulfur

dioxide and 1 ppb ozone [32].

Both supply and return air should be monitored for pollutants by suitable

instrumentation. This is especially true for sulfur dioxide, because books are excellent sinks for sulfur dioxide and a low concentration reading in the

return air would not necessarily reflect low exposure levels [7,48,49].

2.2.6 Particulates

2. 2. 6.1 Damage Caused by Particulates

The effects of particulates on the deterioration of records have apparently not

been well studied, but some effects are obvious and others can be hypothesized.

There is abundant empirical evidence of the visible damage such as soiling of

books and documents. Not only are exteriors disfigured by dust and soot, but

perspiration and skin oils cause dust to become irremovably embedded, not only

on the outside of items, but also on the pages themselves when dust or other

soiling agents are carried on dirty hands.

9
Particles and aerosols exist in a wide size range, from particles large enough

to settle on surfaces because of their weight, to smaller particles that may be

deposited on surfaces electrostatically or thermally. The aerosol concentrations may be determined gravimetrically or by particle count. The weight

methods are most generally used, and are applicable in all but the cleanest

environments. The particle-count methods are applicable in clean- room-type

environments, where the contaminants are usually sub-micron in size [50].

The concentration of large particulates, or dust, that many settle out can be

measured by the weight arrestance test [32,51,52]. Fine, or respirable particulates (diameter roughly 1-10 ym) , can carry adsorbed sulfur dioxide and

nitrogen oxides, and can stain books; their concentration is measured by the

dust spot test, a measure of filter efficiency. The smallest fine particulates

are measured by the dioctyl phthalate test, a measure of ultra-high efficiency

media [32,51,52]. In addition to carrying adsorbed acidic and oxidizing gases

and staining books, particulates can also provide nutrients for mildew growth,

are abrasive to paper and leather, and can change the acidity of paper [7,8].

Viable particulates such as fungal spores and mycelia, bacteria and mold can result in deterioration of books and documents, especially if the temperature

and relative humidity in spaces containing these paper-based materials are not

properly controlled.

2. 2. 6.

2

Examples of Suggested Particulate Concentration Limits

The Canadian Conservation Institute recommends removal of 95 percent of

particulates of diameter greater than or equal to 1 ym and 50 percent of diameter

between 0.5 and 1 ym (which correspond, more or less, to the dust spot and

dioctyl phthlate tests, respectively) [22]. The Royal Ontario Musuem requires

99 percent removal down to 10 ym and 95 percent removal down to 1 ym [10].

Banks [32] recommends as complete removal as feasible of these particulates.

The Library of Congress and the Newberry Library require minimum filter efficiencies of about 95 percent [7,52]. Electrostatic precipitators are not generally recommended for removal of particulates as a stand alone system without

some other conditioning component because they may emit ozone [7,19,53]. Oil

and viscous impingement filters are excluded from use at the Library of Congress

because they can produce aerosols of their own [7].

2.2.7 Biological Agents

Biological agents include fungi (molds), bacteria, actinomycetes , insects and

rodents [8]

.

They do not cause great damage in United States urban libraries

but are more damaging to museums [8]

.

The most important microbial agents in

libraries are fungi, which cause staining, spotting and discoloration, especially, if they produce colored metabolic products [8]. Unlike bacteria, they do

not need liquid water for growth, but do require high relative humidities [8].

Depending on the species, they grow optimally at 15°C (59°F) to 30°C (86°F) [8].

The average optimum temperature is 30°C (86°F) for 95 to 100 percent relative

humidity. They do not tolerate cycling of temperature below and above freezing.

High temperature, especially in combination with high relative humidity, will

kill most fungi and spores. There is little growth below 70 percent relative

humidity; they grow well above 80 percent relative humidity. The optimal

10
temperature near 100 percent relative humidity is about 40°C (104°F) and lower

for lower relative humidities. They grow either in light or dark. Some of

their nutrient requirements can be met by air pollutants, as mentioned above.

Insects are not a major problem in United States urban libraries [ 8 ] . They can

be brought in by people and are attracted by discarded nutrient refuse such as food and candy wrappers, in books and stacks. They are discouraged by low temperatures [ 8 ] . It has been reported that increasing relative humidity increases

the number of insects [ 10 ].

2.2.8 Examples of Design Criteria

Design criteria for archival storage facilities for paper-based materials are reported from several literature sources. Some examples of criteria for temperature, relative humidity, and pollutant concentrations were given in sections

2. 2. 3. 2, 2. 2. 4. 2, 2. 2. 5. 2, and 2. 2. 6 . 2. Some additional examples are given

here. It can be seen that there are in some cases differences in opinion

concerning air quality criteria for archival storage of paper-based materials.

a. ASHRAE [53] recommends that air in archival libraries and museums be filtered

at a particle removal efficiency of 85 percent by the dust spot method.

Relative humidity should be kept at 35 percent for books, and temperature

at 13 to 18°C (55 to 65°F) in book stacks and 20°C ( 68 °F) in reading rooms. Canister-type filters or spray washers should be provided if chemical pollutants are present in the outdoor air. ASHRAE [53] prefers all-air systems

in library areas where steam or water damage may ruin rare books and

manuscripts.

b. A suggested specification by Thomson [54] for museums with regard to gaseous

pollutants is:

Sulfur dioxide not more than 10 pg/m^

Nitrogen dioxide not more than 10 pg/m^

Ozone reduce to trace levels (0-2 pg/m^)

Thomson notes that these levels are readily attainable by present

technology in air conditioning with recirculation. These methods will

also keep concentrations of other acidic gases and oxidants low.

c. A report on the proceedings of a workshop on micro-climates held at the

Royal Ontario Museum in February 1978 [10] gave guidelines for temperature

of 21 to 23. 5° C (70-76°F) and relative humidity of 50 percent + 2 percent

for storage of materials such as manuscripts (paper and parchment) requiring

extremely stable conditions. The recommended performance specification for

micro-climate units requires that the air be filtered for particulate matter

to 99 percent removal down to 10 pm and 90 to 95 percent removal down to

1 pm. Further, the recommended performance specification states that the

air should also be passed through a charcoal or equivalent filter to remove

SO2 , O3 , and N0X .

11
d. Federal Archives and Records Center Facility Standards [55] for long-term

storage require that temperature be kept at 19-23° C (66-74° F) and that

relative humidity be kept at 35-45 percent on a continuous basis.

2.3 SOURCES OF CONTAMINANTS

In addition to the factors that affect paper-based materials discussed in

section 2.2, other sources of contaminants which affect these materials within

archival storage areas include:

• building materials

• books and other paper-based material within the storage area

• human activity within the storage area

• airborne contaminants in the HVAC System (outside air and recirculated

air)

• interactions among contaminants.

2.3.1 Building Materials

The surface areas of the storage facility may be a primary source of

contaminants. Most unsealed masonry emits fine particles due to convection

effects [56]. New concrete has been reported to emit small alkaline particles

for periods up to two years [57], Settling of these particles may cause degradation of materials containing animal or vegetable matter which are of an archival nature, and should be considered a threat to valuable leather bindings

[32]. The extent of damage to paper-based materials caused by masonry, concrete

and other building materials is not known.

Treated wood products can emit acetic acid, formaldehyde, hydrocarbons, and

fine particles into the storage area [9,58,59]. In addition, untreated wood

products can be a source of microbial contaminants.

Some thermal and acoustic insulation may outgas formaldehyde and hydrocarbons,

and may be the source of particulates such as glass fibers, cellulose, and

asbestos [58,59]. Jarke [60] has identified over 200 odorous compounds from

building materials.

Fabrics, including carpeting, drapes and upholstery can be the sources of

several gaseous contaminants such as formaldehyde, hydrocarbons, nitrogen com- pounds, and sulfur compounds [58,59]. In addition, they may emit fine particles

due to convection or re-entrainment effects, and these may also be sources of

microbial contaminants.

Paints, wall coverings and adhesives can also be sources of gaseous and

particulate contaminants including formaldehyde, hydrocarbons, mercury, and

other metallic fumes [58].

Windows must also be considered as a source of contaminants as they provide a means for entry of contaminants into storage facilities. Unless they are tightly sealed, they may allow outdoor contaminants to enter by infiltration.

If windows are openable, little control of contaminants from outdoor sources

12
can be expected during long-term storage. Moreover, windows may also be the

site of condensation during winter months. This latter effect is especially

true in cold climates if high levels of relative humidity may be required to

maintain paper flexibility.

2.3.2 Paper-Based Materials

Books and other paper-based materials stored within the facility may themselves,

be sources of contaminants. Embrittled materials may discharge fine particles

into the air when the materials are handled. Also, autocatalytic deterioration

of book bindings may occur under some air quality control strategies (section

4). Products that consist of, or contain nitrocellulose, such as pyroxylin or celluloid, may release nitric acid which promotes decomposition of paper-based

materials [61]. The deterioration of cellulose acetate is also autocatalytic.

2.3.3 Human Activity

When the storage facility is occupied, thermal, gaseous and particulate

contaminants are generated by the occupants. At sedentary activity, a typical

adult will dissipate energy at the rate of approximately 120 watts, about one- fourth of which is a latent component. Associated with this heat dissipation

is the uptake of about 40 g/hr oxygen (O2 ), and the dissipation of about 30

g/hr carbon dioxide (OO2 ) and about 30 g/hr water vapor. As the human activity

increases, the uptake of O2 and dissipation of CO2 , water vapor, and heat may

increase to values up to ten times sedendary for short periods of time [62]

Skin flaking from humans is also a source of particulate contamination. The

average adult sheds approximately 7 x 10^ particles/minute, and each particle

may contain up to four bacteria [63]. In general, Wang [64] estimates that at

least 15 bioeffluents can be identified with human occupancy. More than 2,000

compounds have been identified from tobacco smoke [58].

Other human activities in adjacent rooms that can contribute to thermal,

gaseous, and particulate loads in archival storage areas include: laboratory

and workroom activities; food preparation, disposal, and dishwashing; health

care and personal grooming; office work; and housekeeping activities.

2.3.4 HVAC Systems

Heating, ventilating, and air conditioning systems can be sources of gaseous

and particulate contamination if they have not been properly designed or are

not properly operated and maintained. Contaminant sources in these systems

include improperly maintained filters, heating and cooling coils, humidifiers,

and ductwork. Particularly important are improperly pitched drain pans asso- ciated with cooling coils and some humidifiers. These can be environmental

niches for the growth of viable contaminants. If HVAC systems do not function

properly, they may introduce excessive concentrations of contaminants from the

outdoor air, recirculate excessive concentrations within the system, or cause interactions to occur within the system. Amines or other organic volatiles

used in steam humidification systems may be sources of contamination. Ductwork

systems have been found in some instances to be contaminated with dust, bacteria,

13
and fungi. If this is the case, they should be cleaned and sanitized depending

on the type of contamination.

2.3.5 Interaction of Contaminants

When contaminants are present in various combinations, the possibility exists

that reactions can occur that result in contaminants other than those originally

emitted into the space. An example of the interactions that might be of concern

in archival storage facilities include reactions between acidic gases, such as SO2 , and water vapor which results in dilute concentrations of H2 SO4 in the pre- sence of catalysts such as metal fumes [32] . Another example of an interaction

is the rate of growth of microbial contaminants as influenced by the relative

humidity in the space [65] . A third example is the affect on fading of dyed

materials caused by the presence of certain wavelengths of light, relative

humidity, and acidic gas concentrations [5,66].

2.4 WORKSHOP ON ENVIRONMENTAL CONDITIONS FOR ARCHIVAL RECORDS STORAGE

A Workshop on Environmental Conditions for Archival Records Storage was held at

the National Bureau of Standards on January 19-20, 1983. The objectives of the

Workshop were to explore the rationale for establishing levels of air quality

for archival storage and to review equipment technology with regard to its

capability to provide special or recommended environmental conditions for

archival storage facilities. Among the Workshop participants were experts in

the preservation and conservation of paper-based materials and artifacts, and

experts in environmental conditioning technology. The environmental conditioning experts were selected by NBS because of their leadership activities in the

American Society of Heating, Refrigerating and Air Conditioning Engineers

(ASHRAE) . Most of them were chairmen of subcommittees or task groups of ASHRAE

which had interests that were applicable to environmental conditioning of

archival storage facilities. Although the participants with environmental

conditioning technology expertise were drawn from the ASHRAE membership, they

served as individual professionals and not as ASHRAE representatives. A list

of the Workshop participants is presented in appendix A.

The Workshop provided a forum to discuss the needs for air quality for records

storage and the capabilities of environmental conditioning components and systems to satisfy those needs. The Workshop participants also assisted in providing references which were used to document the air quality criteria for archival

storage presented in section 3. A report of the Workshop was prepared by the

environmental conditioning experts with the assistance of some of the experts

in conservation and preservation [2]

.

Much of the information from the Workshop

report is contained in this report, and some of the participants are coauthors

of this report.

14
3. DESIGN PARAMETERS

In the design of environmental conditioning systems to control the air quality

in storage areas or facilities for paper-based archival records, the following

actions are recommended:

a. Establish acceptable air quality criteria.

b. Determine appropriate methods to control air quality.

c. Establish methods of performance evaluation of environmental

conditioning systems.

d. Design the environmental conditioning system.

e. Establish a maintenance program to ensure that required environmental

conditions are maintained.

These recommended actions are presented to aid the designer and are addressed

in sections 3, 4, and 5 of this report. This section deals with the parameters

to be considered in the design of archival storage facilities.

The efforts to achieve acceptable air quality control in buildings in which

archival records are stored should be limited to those storage areas which con- tain paper-based archival records, paper-based documents of intrinsic value,

records that by law must be kept in their original form, and records that cannot be duplicated in time to prevent the loss of information. Other spaces in

the same buildings should only be considered as they affect the storage areas. The archival conditioning system should be designed to isolate the archival

storage spaces from other building spaces.

Air quality criteria for the design of archival storage facilities are given in

table 3, section 3.6. Some of the environmental factors included in the criteria, dry-bulb temperature, relative humidity, gaseous contaminants concentrations (SO2 , N0X , and O3 ), and particulate contaminant concentrations, are considered in the following sections in terms of expected outdoor values and

in terms of desired or required indoor values with regard to preservation and

conservation factors, human factors, architectural factors, and economic factors.

3.1 EXPECTED OUTDOOR LEVEL OF CONTAMINANTS

The levels of concentrations of gaseous contaminants inside the National

Archives Building, the Madison Building of the Library of Congress, and the

East Wing of the National Gallery of Art were measured by NBS and compared to

the outdoor levels of air concentrations of these contaminants. Outdoor air

concentrations of SO2 , N0X , and O3 are monitored at 24th and L Streets by the

Washington, D.C. government. These data, recorded on a daily basis and corresponding to the dates of NBS indoor measurements of concentrations of the gaseous contaminants (section 6 . 2 . 1 ) indicate that concentrations close to the

upper limits of Environmental Protection Agency (EPA) Primary Standards must

be expected. Airborne concentrations of particulate matter, both outdoors and

indoors, were not monitored nor were data obtained by NBS during this study.

Thus, macro-environmental measurements for the Washington, D.C. area obtained

from the EPA must be relied upon. These data also indicate that the upper

limits of the Primary Standards for particulates must be expected. In general.

15
outdoor dry-bulb temperature and relative humidity data may be obtained for

different areas of the United States from the National Oceanographic and

Atmospheric Administration (NOAA) [67] in three-hour increments on a yearly

basis. Design winter and summer conditions may also be found for most parts

of the United States in the ASHRAE Fundamentals Handbook [ 68 ]. For purposes

of this report, the outdoor conditions may be summarized from the information

given in tables 1 and 2 .

3.2 PRESERVATION AND CONSERVATION FACTORS

In addition to the recommended air quality criteria (section 3.6), several

other factors should be considered. They include:

• Dry-bulb temperatures should be maintained at the lowest acceptable

temperature in archival storage facilities to reduce the rates of

deterioration of paper-based material.

© Relative humidity should be maintained within limits of 35 to 45

percent to control paper flexibility and microbial growth.

® Stability of temperature and relative humidity control within narrow

limits is needed to reduce fatigue cycles and minimize deterioration

rates of paper-based material.

© Concentrations of SO2 , N0X and O 3 should be minimized to reduce

deterioration of paper-based material.

© Gaseous and particulate contaminants emanating from building materials

and furnishings in storage areas must be minimized.

o Use-areas and offices should be separated from storage areas and have

separate environmental conditioning zones.

• Environmental control of adjacent areas may affect control of the

storage areas.

• Access to archival records should be controlled. Information is

required regarding the expected length of undisturbed storage of the

material, where the stored material will be used upon access, how long

the material will remain out of storage, and what controls of human

activity will be exercised.

3.3 HUMAN FACTORS

Although the primary design parameters are for the archival records, conditions

to be maintained in the storage areas must be compatible with human occupancy.

Thus, air quality criteria must also be considered in terms of human health

and comfort. With regard to human occupancy, a primary factor is the length of

time the occupant will be exposed to the environment within the storage area.

If the exposure time is short and infrequent, the thermal air quality control

may be less defined by the human needs than by the requirements for minimizing

16
Table 1 Summary of Outdoor Air Contaminants and Concentrations Given

In National Ambient Air Quality Standards 3 *^ /

Air Contaminant

Long Term Short Term

Level Time Level Time

Carbon Monoxide 40 mg/m3

1 hr

10 mg/m3 8 hrs

Lead 1.5 Mg/m 3 3 mo Nitrogen Dioxide 100 Mg/m3 yr

Oxidants (Ozone) 235 Mg/m3 1 hr

Particulates 75 Mg/m3 yr 260 Mg/m3 24 hrs

Sulfur Dioxide 80 Mg/m3 yr 365 Mg/m3 24 hrs

Notes: }J Prom ASHRAE Standard 62-1981 [69].

£/ See Reference 11 in ASHRAE Standard 62-1981. Pertinent local

regulations should also be checked. Some regulations may be more restrictive than those given here, .and additional substances may be regulated. The values given are from U.S. Environmental Protection

Agency National Ambient Air Quality Standards.

Table 2. Summary of Outdoor Air Thermal Design Conditions for the Washington,

D.C. Area, (Washington National Airport) from 1981 ASHRAE Fundamentals

Handbook [68].

Winter Summer

Dry- bulb temperature -8.3° C (17° F)J/ 32.8* C (91* F)J/ Mean daily range 10* C ( 18* F)

Wet-bulb temperature 23.3* C (74*F) 3/ 24.4* C (76*F)^

Degree-days

18.3° C (65° F) base 2347 (4224) 828.3 (1491)

]J Temperatures exceed this value 97.5 percent of the time during the winter.

Conversely, temperatures are at or below this value 2.5 percent of the time

or 54 hours during the months of December, January, and February.

£/ Temperatures equal or exceed this value 2.5 percent of the time or 73 hours

during the months of June, July, August and September.

2/ Coincident with aummer dry-bulb temperature.

17
the deterioration of the stored material. However, if the exposure times are relatively long or frequent, control values should be defined to a greater

extent by the requirements of the occupants, or consideration should be given

to alternatives of long exposure, such as removal of a document from the storage

area to a separate workroom.

For the air contaminants shown in table 1, the recommendation in ASHRAE Standard

62-1981 [69] is that the indoor concentrations not be allowed to exceed the

National Ambient Air Quality Standards for outdoors. Thus, the lower concentrations required for preservation and conservation control will be the more stringent and thus will be the limiting criteria.

Humidity control for human occupancy is recommended by ASHRAE Standard 55-1981

[6] to be within the range of 1.7-16.7°C (35-62°F) dew-point temperature.

Generally, this range may be considered to be associated with 30-65 percent

relative humidity. The range of 35-45 percent relative humidity for preservation and conservation control is more restrictive but acceptable for human

occupancy, thus the narrow range will be the limiting criterion.

In addition to relative humidity and exposure time, five factors must be

considered when defining the thermally acceptable conditions for human occupancy: dry-bulb temperature, mean radiant temperature, air movement, human

activity level, and thermal insulation of the occupants' clothing [6]. For

those conditions in which relative humidity is near 50 percent, the mean radiant temperature is approximately equal to the dry-bulb temperature, the required

air movement in the occupied space is less than 0.2 m/s (40 f pm) , and the

activity level of the occupant is near sedentary. The value of the clothing

insulation is expected to be at least 1.3 clo,i/ if the dry-bulb temperature is

to be maintained at or below 18°C (65°F) for exposure periods of longer than 1 hour. - .

3.4 ARCHITECTURAL FACTORS

The design of the successful archival records storage facility is a joint

function of the architect and engineer, and it is incumbent upon both the

engineer and architect to identify and coordinate basic architectural consider

ations that must be incorporated in the final design. Some of these considerations are functional relationships between areas, selection of building

materials, and selection of furnishings within the storage area. In addition

to the architectural considerations listed in this section of the report, the

reader is referred to Federal Archives and Records Center Facility Standards

[55] which include many other factors to consider in the design of these

facilities.

a. Separation of areas - The stack area should be isolated from general

public use areas, and from reading rooms. Suitable security

1/ Clo value is a numerical representation of a clothing ensemble's thermal

resistance, 1 clo = 0.155 m^ K/W (0.88 ft^ h F/Btu)[6].

18
arrangements should be made in order to limit access to these spaces

to authorized personnel.

b. Water problems - The avoidance of any potential water-related problem

is important. All toilet areas, drinking fountains, and other sources

of potential water leaks should be excluded from the stack area, and

from any area above the stack area. Required fire protection systems

such as automatic sprinklers, may present a problem, and special

shutoff type heads may be desirable in order to limit water damage in case of a fire. Water control valves on the sprinkler system should

be provided with tamper switches and be connected into the building

fire alarm system [55]

.

The use of floor drains in the stack areas may also be indicated, if the plumbing system is designed to prevent reverse flow from sewer backup.

c. Mechanical equipment areas - All mechanical equipment components must

be located in separate rooms outside of the stack area, and not located

directly above stack areas. Where local devices such as reheat coils

or humidifiers are required, they should be located in a space outside

the stack areas. All mechanical components should have adequate space

for proper maintenance.

d. Pressurization - Pressure relationships between different areas must

be maintained. In general the stack areas will be designed to operate

under a positive pressure as referenced to the outside, and to other

areas in the building. All door openings should be controlled, and

openings in walls and ceilings must be closed off to minimize

exfiltration from the stack areas in order to maintain positive

pressure.

e. Interior finishes and furnishings - All wall surfaces, ceilings, and

floor coverings should be selected of suitable material to minimize

the generation of particulates, and to minimize outgassing from the

materials. This criterion is also applicable to any interior

furnishings in the stack area.

f. Relative humidity - All exterior surfaces must be analyzed to ensure

that condensation will not occur under the maximum indoor relative

humidity during the coldest winter weather expected. With existing

older buildings, this may prove to be a problem, and methods must be

undertaken to modify the exterior walls by adding insulation and vapor

retarders where it is predicted that condensation could occur. Attention must also be given to any exterior glazing, and if present,

multiple glazing may be required.

3.5 ECONOMIC FACTORS

For any paper-based material to be classified as an archival document or as a document of intrinsic value, an implication exists that the benefit of storing

it with minimal deterioration is worth a significant financial investment. Present methods of providing the required environmental control for these documents

19
generally are based on minimizing both first and operating costs of the systems.

That is, systems are usually designed and installed on low bid, and they are operated with minimum budgets. Both aspects of this procedure are usually

unsatisfactory in maintaining the desired environmental control. More rational

methods for considering the importance of economic factors in controlling the

environments for archival records may be based on life-cycle costs, benefit-cost

analysis, or risk assessment. These methods include consideration of the

following economic factors:

• Initial costs - including planning, design, and installation.

• Operational costs - including labor costs and supplies for maintenance

and normal repair.

• Energy costs - including fuel consumption and demand charges.

© Replacement costs - including salvage, relocation costs, and related

factors.

© Cost of capital - including interest on both debt capital and equity

capital.

• Inflation rates - including projected increased costs for materials,

labor, maintenance, and repair.

• Life expectancy - including components, systems, and buildings; also

the life expectancy of the stored documents.

The economic methods must be applied to three different problems relating to

these storage facilities:

a. Alternatives available to provide acceptable control in existing

facilities which presently contain inadequate systems (i.e., retrofit).

b. Alternatives available to provide acceptable control in existing

buildings which presently have no control systems (i.e., remodel or rehabiliation)

c. Alternatives available to provide acceptable control while plans are being developed or implemented for a new facility.

Several economic models are available for each of these cases, and some are included in reference [70].

Application of these models will often provide alternatives which may appear to

be more expensive than that usually determined from low bid first cost policy,

but may in the long-term prove to be most cost-effective. For example, many

cases exist in which present equivalent costs may be minimized or inflationfree rates-of-return may be maximized by allowing increases in first costs and

preventative maintenance costs if the energy efficiency, reliability, and

longevity of system operations can be increased.

20
3 . 6 RECOMMENDED AIR QUALITY CRITERIA FOR ARCHIVAL STORAGE

The recommended air quality criteria for archival storage of paper-based

materials are given in table 3. The criteria are based on information taken

from the literature and from the recommendations of the participants at the

Workshop on Environmental Conditions for Archival Records Storage [2] . Three

categories of storage conditions are given along with the air quality criteria

for each category. The three categories of storage conditions are as follows:

Category 1. Storage facilities for unrestricted public access.

Category 2. Storage facilities with access restricted to authorized

personnel only, but in which documents must be removed and

replaced frequently.

Category 3. Storage facilities with highly restricted access, and in

which documents will be removed and replaced infrequently.

Documents in this storage facility would require 6 to 8 weeks

of pre-conditioning before removal or replacement.

In addition to the air quality criteria given in table 3, the following design

parameters and guidelines are recommended:

A minimum amount of air recirculation is desirable to provide proper air

distribution in the records storage areas and to avoid stagnant areas. A value

of six air changes per hour is recommended for the minimum air circulation

rates, or an air diffusion performance index (ADPI)^/ of at least 80 percent,

regardless of the load calculated from thermal requirements (see section 4.2.1).

Storage facilities should be separated from other areas of the building, and

controlled by a separate system. Pressurization control should be applied so that the storage facility operates under a slight positive pressure with

respect to adjacent indoor areas and to the outdoors.

All building materials and furnishings within the storage areas should be

selected to minimize the emissions of gaseous and particulate contaminants.

For existing facilities, these materials should be treated with appropriate

sealers or be replaced.

All windows in the storage areas should be removed or blocked if possible, or

if not, sealed to prevent opening and to minimize infiltration. Special attention should be given to the possible formation of condensation on windows and

exterior surfaces.

Air diffusion performance index (ADPI) can be defined as the percentage of

locations throughout the occupied zone of an office, or in a storage area,

where measurements were taken which meet the specifications on effective

draft temperature and air velocity. If the ADPI is maximum (approaching 100

percent), the most desirable conditions have been achieved.

21
Table 3. Recommended Air Quality Criteria for Archival Storage

Category of Storage

Conditions 1 2 3

Public Access yes no no

Duration of Storage short-long^/ short-long^/ long£/

Frequency of Access often often seldom

Dry-bulb temperature

range

18-2A 0 C (65-75°F)10-13°C

(50-55°F)

-29°C

(-20°F)

Temperature Cohtrol^-/ + 1°C T+ 2°F)

+ 0 .5° C T+ 1°F) + 1°C

T+ 2°F)

Relative Humidity A0 - A5Z 35% 2 X^J

Range and Control^/ ± 5Z ± 3Z

Gaseous Contaminants

so2 < 1 ug/m 3

<. 1 Mg/m 3 < 1 Mg/m 3

N0X< 5 Mg/m 35 Mg/m3 < 5 Mg/m 3

°3 <_ 25 Mg/m3 < 25 Mg/m3 < 25 Mg/m3

CO2 A. 5 g/m3 £ A. 5 g/m3 < A. 5 g/m3

HC1

Acetic Acid HCHO

use best

control

technology

use best

control

technology

use best

control

technology

Fine Particles

TSP^/ < 75 Mg/m 3 < 75 Mg/m3 < 75 Mg/m 3

Metallic Fumes use best

control

technology

use best

control

technology

use best

control

technology

Temperature should be in the given range and should not vary more than these

control values.

£/ Relative humidity should be in the given range and not vary more than these

control values.

2/ Total suspended particulate: the weight of particulates suspended in a unit

volume of air when collected by a high volume air sampler.

2/ Short-long term storage is defined in this table as a yide range of time of storage. Documents may be removed and replaced daily or stored for many

years depending on requests for their use.

£/ Long-term storage is defined in this table as a time of storage intended to

be 50-100 years or more. Documents designed for this type of storage would

be those of "intrinsic value" and designated for preservation as long as possible.

2/ Two percent relative humidity at normal room temperature. At the temperature

of storage, -29°C (-20° F), the water vapor in the sealed storage container

is close to saturation (i.e., 100 percent relative humidity).

NOTE: It may be desirable to provide system capability to achieve lower levels

of temperature and relative humidity than the levels given in this table. Some studies tend to indicate that for long term storage either or both

lower temperature and lower relative humidity may be desirable.

22
4. AIR QUALITY CONTROL

4.1 STEADY-STATE MODEL FOR AIR QUALITY CONTROL

A simple, steady-state expression for a one-compartment model of the storage

facility is helpful in identifying the three methods of control most commonly

employed for thermal and air quality control: source control, removal control,

and dilution control [62,71], A mass-balance for the model shown in figure 1 may be expressed as:

V o

where:

AC = Cr - CG = the difference between the uniformly-mixed indoor air

concentration, Cj- , and the outdoor air concentration, CQ

.

• • • • N = Q

- S = the net generation rate of the contaminant where Q is the source strength (i.e., gross generation or emission rate), and S is

the sink strength (i.e., settling or sorption rate within the

controlled space).

• • E = £Vra Cu

= the removal rate of a contaminant in the air cleaner;

e = the efficiency of the air cleaner rate in terms of the contaminant

removed; Vm = volumetric flow rate of recirculated air; Cu

= con- centration of the contaminant, upstream of the air cleaner, and;

Cj = concentration of the contaminant, downstream of the air cleaner

(see figure 1);

VQ = volumetric flow rate of outdoor air for dilution control.

In the model, the dilution rate, VQ , represents infiltration, natural

ventilation or mechanical ventilation with outdoor air. The removal rate, E,

represents fan-filter modules now available as consumer products, or filtered

100 percent recirculated air commonly used in residential forced air systems.

In figure 1 , V r represents volumetric flow rate of indoor air for dilution

control

.

Although Eq. (1) was derived from a simple model, it serves to identify some control strategies and their limitations for indoor air quality control:

• If removal control is not employed, the indoor concentration will exceed

the outdoor concentration unless the source is removed or an infinite

dilution rate is provided.

• If the indoor contaminant concentration is to be less indoors than

outdoors and the dilution rate is finite, the removal rate , E, must

exceed the net generation rate, N.

23
o Outdoor air required for dilution control may be reduced, if alternative

source control and removal control strategies are sufficient to provide

the same quality of indoor air as would be achived by dilution control ,

• To achieve an acceptable AC, economically, a combined strategy of

source, removal, and dilution control may be required.

E = 8 V m C u Removal rate

Figure 1. One-compartment, uniformly-mixed, steady-state model for

indoor air quality control

Whether an indoor air quality control strategy employs an open-loop or closedloop system, Eq. (1) indicates that the contaminant concentrations, Cr and CQ , must be known or specified and that the net generation rate, N, must be known

or estimated if indoor air quality is to be controlled directly. In this

regard, it should be noted that Eq. (1) is analogous to an energy balance in

which N may be compared to the cooling load within an occupied space; AC to the

change in enthalpy required to cool the supply air; and V 0 to the volumetric

rate of supply air.

4.2 COMPONENTS AND SYSTEMS

To achieve acceptable air quality control in archival record storage facilities,

three types of control systems must be considered individually and collectively;

temperature and relative humidity control, control of gaseous contaminants, and

control of particulate contaminants.

4.2.1 Temperature and Relative Humidity Control

In general, it is expected that only air systems will be used in stack areas,

as any steam or water system will present the possibility of water leaks. In

a restricted stack area, the impact of people will be minimal upon the thermal

and humidity loads from the space. Usually, lighting and transmission loads

24
will be the major space consideration. These may be expected to remain fairly

constant, although lights may be on during the day and off at night, and the

required circulation air quantity, in terms of cfm per square foot, may be

quite low. A minimum amount of air recirculation is desirable to provide

proper air distribution in the space and to avoid any stagnant areas. A value

of six air changes per hour, or an air diffusion performance index (ADPI) of at

least 80 percent [72], is suggested for the minimum air circulation rates,

regardless of the load calculated from thermal requirements (see section 3.6).

A constant volume, variable temperature system will probably most often be

selected for stack areas. Little variation in temperature and humidity is

usually expected within a stack area, so rather large control zones will

probably be selected.

Reheat systems are commonly used, and with the proper selection of air

temperature after leaving the coil, the amount of reheat can be minimized.

Additionally, a hot refrigerant-reclaim circuit should be considered for this

reheat energy during operation of refrigeration equipment.

Because the quantity of air that is circulated, based on filtration and

distribution criteria, will usually be greater than that required for temperature and relative humidity control, a bypass or primary- secondary air handling

arrangement may be used. It may be possible to provide cooling and dehumidification for only the outside air, or for a portion of the total recirculated air.

Winter humidification can be provided by several methods, however, the steam or evaporation type as opposed to atomizing type is preferred in order to minimize

airborne particulates. Humidification may be added in the central air handler

or individually as zone humidifiers.

A summer cooling coil should be provided for all systems. This will generally

be a chilled-water system, as better control is obtainable, although with

smaller systems direct expansion may be quite feasible.

Many systems have used a sprayed-coil system or an air washer. Air washing

equipment provides a means of partial contaminant control, as well as a source

of winter humidity. However, significant problems have been experienced in

the long term operation of sprayed coil systems, generally consisting of extensive corrosion, scaling of the coil and fin surfaces, and bacterial growth in

the water spray pans. In general, the use of a spray coil or air washer system

should be used only when it can be assured that the materials of construction

and owner commitment to maintenance will ensure long term operation.

For Category 2 Storage Conditions (table 3), the specified temperature of 10-

13°C (50-55°F) and 35 percent relative humidity will be difficult to achieve

with commercial equipment. Thus, low- temperature refrigeration and dehumidification equipment will probably be required. The economics of each project will

dictate whether indoor design conditions must be modified so that commercial

HVAC equipment can be used. Specially designed facilities and environmental

conditioning systems will be required for Category 3 Storage Conditions (table

3). The design of these facilities is not addressed in this report.

25
Construction materials for the HVAC system should be those that would tend to

have long life, and would lend themselves to convenient maintenance. The duct

systems should generally be unlined galvanized sheet metal, insulated externally

where required. For wetted coil casings and drain pans, the use of stainless

steel should be investigated. Air handling systems should be arranged such

that easy access is obtained between each component for servicing and cleaning.

In general, the traditional outdoor air economizer cycle is not recommended for

these systems, as it would tend to introduce excessive amounts of outdoor pollutants. Thus, other energy efficient strategies should be implemented; e.g.,

heat reclaim chillers, using the recovered energy for reheat; or free cooling

cycles; or using cooling tower circuits for reheat.

Economic considerations may govern whether standby equipment is specified for

components of the refrigeration and air handling systems. Short term outages

of the HVAC system may not cause excessive damage to the stored materials, thus

complete redundancy in the HVAC system may not be necessary.

A. 2. 2 Control of Gaseous Contaminants

The two most common methods of cleaning air of gaseous contaminants are by

application of granular beds and wet scrubbers. The state-of-the-art of these

air cleaning methods along with other methods have been reported by an Interagency Research Group on Indoor Air Quality [73]. It can be seen from the

following sections (A. 2. 2.1 and A. 2. 2. 2) that the control of gaseous contaminants using granular beds or wet scrubbers requires an intensive maintenance

program to assure their performance over time.

A. 2. 2.1 Granular Beds

The typical compromise between the objectives of achieving effective gas/solid

contact with a granular bed and of minimizing resistance to air flow is realized

by selecting granule sizes in the range of 6 to 1A mesh. With such granulation,

the half-life of a molecule in the gas phase (before it reaches the surface of

a granule) is about 0.01 second [7A ,75] • Then, if an air stream that contains a concentration of contaminant, Cr , enters such a granular bed, the concentration

of contaminants that have never reached the surface of a granule after n seconds

of residence time, Cn, is:

-lOOn

Cn = Cj. (2 ) (2)

The ratio of C^/Cj. is the penetration, P, of the granular bed. Thus, the

contact efficiency, e, (fraction of molecules that have contacted a solid

surface) is:

-lOOn

e = 1 - (2 ) (3)

This efficiency term is identical to that described in Eq. (1) and figure 1.

Examples of the relationship between residence time, n, and contact efficiency

of a granular bed are shown in table A.

26
Table 4. Relationship between Residence Time, n, of a Gaseous Molecule in

a Granular Bed and the Contact Efficiency, e, of the Bed

Residence

Time (sec.)

-lOOn

2

0.01 0.500

0.02 0.250

0.03 0.125

0.04 0.0625

0.05 0.03125

0.06 0.01562

0.07 0.00781

-lOOn

e = ( 1-2 ) x 100%

50.0%

75.0

87.5

93.75

96.88

98.44

99.22

There are other factors to consider:

a. What fractions of the molecules that reach the solid surface are retained there?

b. Is the retention on the surface reversible?

c. What is the capacity of the granular medium for retention of the

contaminant?

These questions should be answered in reference to the media commonly used in

central HVAC systems. Only two substrates are in common use: activated carbon

and activated alumina. Silica gel, synthetic zeolites, and other materials are sometimes used in small, room-type air purifiers sold in the consumer market.

However, these latter materials are not generally available for use in central

HVAC systems (either residential or commercial).

Activated alumina is used only with chemical impregnations; however, activated

carbon may be used with or without impregnation, depending on the application.

Tables 5 and 6 summarize the actions of these media.

4. 2. 2. 2 Wet Scrubbers

Acidic gases can be scrubbed by alkaline solutions. However, after all of the

alkali is neutralized, the scrubber liquid will become acidic and corrosive.

Thus, maintenace of a basic condition is important. The scrubber pH required

for removal of acidic vapors depends on the strength of the acid. A strong

acidic vapor, such as SO3 , is absorbed even by a strongly acidic solution.

However, a weak acid, such as acetic acid, requires an alkaline solution.

Wet scrubbing for removal of acid vapors can be incorporated with thermal

control strategies to improve energy efficiency and life-cycle costs. However,

when these control strategies are combined, additional monitoring may be

required or chemical imbalances can result in deterioration of the archival

records, deterioration of the mechanical equipment and more expensive

maintenance and repairs.

27
Table 5 . Summary of Actions of Activated Alumina (AI2O3)

Impregnation Mode of Action Reversible?

None (substrate only) Removes water in preference to other vapors.

Not applicable to air cleaning. Yes

Potassium

permanganate

KHnOA

As oxidizing agent; it reduced to MnC>2 (brown). No

Effective for formaldehyde (HCHO) and sulfur

dioxide (SO2), but information on total capacity

is not available from refereed journals.

For reaction to occur, some moisture must be present, because the action is electrolytic.

KMn04 is reduced to Mn02 even by water, so its lifetime is limited, at best. However,

Mn02 is a catalyst for air oxidation, so some easily oxldizable contaminants continue

to be oxidized, but reactions are slow.

Sodium carbonate

(Na2 OO3) or bicarbonate

(NaH 003 )

Reacts with SO2 by acid-l^ase neutralization No

SO2 + Na2003 Na2S03 + OO2

Table 6. Summary of Actions of Activated Carbon

Impregnation Mode of Action Reversible?

None (substrate

only)

Physical adsorption and capillary condensation. Yes (except for

Applicable to a broad range of organic contain- the oxidation)

inants, generally with molecular weights larger

than 50 .

Also adsorbs SO2

Some catalytic oxidation (H2S sulfur)

Sodium hydroxide

(NaOH) or potassium

hydroxide (KOH)

Neutralization of acidic gases, SO2, H2S, NO2,

HC1 , acetic acid. Reaction is, for all practical purposes, instantaneous. Now used

extensively for removal of H2S from sewer

gases.

Capacity depends on amount of caustic used in

Impregnation, but can be enhanced by some catalytic oxidation on carbon surface.

H2S + 2 KOH K2S + 2H2O

f oxidation

t c S

(K2S n ) (polysulf ides) Some SO2 oxidized to

SO3 - H2SO4 (retained on carbon)

28
4.2.3 Control of Particulate Contaminants

The particulate filtration system must be capable of continous operation with

planned maintenance cycles of no less than three months. The system should be

capable of removing at least 85 percent of 0.5 pm particles in each pass of the

recirculating air stream through the filtration system when tested in accordance

with ASHRAE Testing Standard 52-76 dust-spot method [51,76]. If special emphasis is put on the finer particulates (e.g., condensed acid aerosols), electrostatic filters, which offer a relatively "flat" collection efficiency vs. particle-size relationship can offer a real advantage. Upgrading the final

filter to the high efficiency particulate air (HEPA) filter range of at least

99.97 percent collection efficiency of 0.3 pm DOPj/ particles, will offer

better protection from the smaller particles [77]. The combination of electrostatic charging of HEPA final filtration offers unique advantages in the lower

submicron particle range [78].

To meet the design parameter of a three-month minimum planned maintenance

schedule, it is important that a roughing filter be included in both the outdoor air supply system and in the recirculating air system, prior to the highefficiency filter section. If the outdoor air is injected into the recirculation system downstream of the protected area and upstream to its roughing

filter, that roughing filter can serve as protection from both the outdoor and

recirculating air.

It is recommended that the roughing filters be roll-type filters using glass

fiber media, and that an electrostatic filter be used next in the system, either

as a collector or as an agglomerator ahead of high efficiency barrier filters.

The reason for this recommendation as stated earlier lies in the added protection in the ultra-fine aerosol range, and in the extension of useful life of

the barrier filters [79]

Note that the 85 percent discoloration efficiency

target can be reached, or exceeded, with barrier filters alone. If first-cost

is of primary importance, this alternative may be worthy of consideration.

Extended barrier filter life, and improved ultra-fine aerosol removal will

result from inclusion of electrostatic filter in the system. (Note: Typically,

electrostatic filters result in less than 0.05 ppm increase of O3 in the air

stream, less than usually found in outdoor air. Further, it is expected that

the carbon, or other gaseous filtration material will easily remove even this

small amount. It may be further noted that the addition of O 3 in a gascontaminant cleaning system can enhance retention of acid gases.)

The barrier filters should be extended-surface filters, either of envelope or pleated-paper configuration. They should be capable of attaining the 85 percent

dust-spot efficiency target and should have a dust-holding capacity exceeding

the targeted maintenance schedule with the dust load described earlier [79,80,

81]. Again, if special attention is to be given to the ultra-fine aerosols,

consideration may be given to upgrading these barrier filters to the HEPA range

]J Particle removal performance of

filters is normally established

Reference MIL-STD-282 [51,52],

high efficiency particulate air (HEPA)

by the DOP Smoke Penetration Method,

29
of efficiency, or to just adding the HEPA filters downstream of the regular

high efficiency barrier filters to take advantage of still further extension

of HEPA filter life [82,83].

Typical initial costs for the various kinds of filters described above, their

operating resistance or electrical demand, and estimated service life for

archival storage facilities are shown in table 7. This information should be

used in comparing the order of magnitude, only, of owning and operating costs

for alternative specific systems (system sizes greater than 25 m^/s or 50,000

cfm)

A rigorous maintenance program, as with gaseous contaminant control systems, is

vital to the continued desired performance of particulate removal systems.

4.2.4 Integrative Control

As indicated in the description of the one-compartment model, figure 1, three

methods of control are available for thermal loads, gaseous contaminants, and

particulate contaminants. These are source control, removal control, and dilution control. The suggestion was also made that, to achieve an acceptable

level of concentration in the controlled space economically, a combined control

strategy may be needed. As indicated in section 4.2.1, the supply air rate for

thermal control may be greater or less than the removal rates needed for gaseous

or particulate control. Also, if human occupancy is expected, a minimum amount

of outdoor air will be required for ventilation (i.e., the supply of C>2 and

dilution of CO2 ) of the occupied space. Beyond these minimum conditions, the

supply air rate and percent of outdoor air (dilution control) and air cleaner

efficiencies (removal control) may be optimized economically within the

constraints of acceptable environmental control for the paper-based materials.

It is also noted that optimizing between dilution control and removal control

presuppposes that source control is more cost-effective than either of the

other alternatives, and therefore, that indoor generation rates have been

minimized.

30
Table

7.

Estimated

1983

Costs

of

Installing

and

Operating

Various

Particulate

Control

Devices

cO

B o CO >4-1 •H 0) 4-> CJ bO 1 p 1 1 ui cO 1 cO O 1 1 CJ CD 1 & o 1 1 0) d3 o i—1 o w CM

0) o O o

bO

U CM <u CM CM

CD

dd Sd rH Pd Pd bO •H cO XI

cO 4J • •H • 9 cO CO c bO d d

0) •H •H •H •rH •H > 0) CD r-4 C & <d 00 00 m o pi • 0) . 9 o d o i-H

at 1—1

4-4 r-H

d

BB

cO CJ X2 cO 4-4 44 S 4-1 •H iH d o o

cd CD LO bO cO 0) "

d rQ o •H d 4-1 -ct U0

0)

O o { d

d

O •H

pi • bO cO *H 9 9 o CD 6 cO O O </> d B </> </> o d

X) XlX •H CD

d

d 13 /-Nd bO

d •H

0) cd •H •H

d

M -H l-id o XI >4

4-1 o xd CD xd •H <d xd cd

O •H >4

d

M

t—( d CD 0) 4J 0) •H xd 4-1 0) 4-1 •H X2 4-1 cO cO •H U cO \—l

XP iH XP cO CD i—1 ^ r-l CD bO

O XP

>4-1 o d

d v— •H xo •H ^ -H

OM

Md CD V4

CD

X 4-4 o 4-4 4-1X CD cO o i—l CD 4-1 CD CD 4-1 CD CD CD •H CO 4-1 d CD M CD d d

bO 4-1

d xd CO CD xd bO xd

d CO bO xd bO cj cO >> CO CD

cO •H •H o Si xd 4-1

d 4-1 o U xd

d 4-1

d CD (D

X CD CJ

u XI CO CO 4-1 4-1

d •Hd

x (D 4-1 •H

d •H i—1 rH

O

d l-l i-H V4 (-1 CD S d d o xd o 4-1 d d xd o xd CD o »“H •H <D CJ CD CD > o o e bO B o cO o bO B bO xd 4J C4 4J <C B B d <D <D 6 d d X 1 CD iH (-4 rH o o r—1

rH o m o d •H Xd •H •rH

m •H 00 on r-H S-4 CM CD CJ X) x t—H x cO cO m V. ' 4-1 CO 00 4-4 B B B

4X r-s 4-1 4-4 4-4 CD X CJ CJ O O CD —, O i-H x> m o i—1 o 00 r-H 6 i—1

cO • 9 • 4-4 CO 4X o O o CJ •H CD 1 1 1 4X d m o m o •rH *H o OO o CM d W 9 9 9 • M O o O O CO- <o- co- <oCD 4X .

CO CD CD P4

i—1

cO 4-1 • d u <D CD o

CJ CD 4-1 t-4 XI

H

d

O S~i . •h d i-H •H CD /—N CD X d CD Q 4X cO •H cO CD 1-4 4J CD 4J

S-I CD 4-1

d

O rH 4-1 *H i—4 cO iH CJ r 4-1 •H d O •rH CTN

Ol, o CD •H cO 4-4 CD -H 44 o> a d CD X O 4-1 /\

4-1

M >% o X CD J-l l-l 4-4 1-4

O -H 4X 0)

B CD CD CD <D 0\ < 1 4J d o •H a •H < CD r-H CJ cO i-H U 4J X PP a i—1

CD CD bO !-i

m o w o i—! i—1

bO cO 00 C4 cO nd * Pi W CJ cO Wv CD PQ

31

Estimates

based

upon

the

January

19-20,

1983

Workshop

on

Environmental

Conditions

for

Archival

Records

Storage,

National

Bureau

of

Standards.

To

convert

from

ft^

to

m3

multiply

by

2.832 x

10'
5. PERFORMANCE EVALUATION OF ENVIRONMENTAL CONDITIONING SYSTEMS

Experience in museums and libraries has provided abundant evidence that

environmental conditions are by no means necessarily what they are assumed to

be on the basis of system capability or central control stations, particularly

as HVAC systems age, personnel change, and buildings are altered. Thus the

importance of a well-designed and carefully executed monitoring system cannot

be overemphasized. Moreover, if the purpose of climate control is the preservation of valuable cultural property, it follows that the responsibility for

monitoring environmental conditions should rest with those primarily responsible

for the preservation of the collections.

For successful performance evaluation, two procedures are needed: monitoring

procedures and assessment procedures. Monitoring procedures are needed for

data acquisition, and assessment procedures are needed for data analysis. With

these procedures, the performance data, obtained through monitoring the systems,

may be compared to the specified performance criteria, and compliance with the

criteria may be assessed. If compliance is achieved, no specific action is

required, but the procedures should be repeated periodically. If compliance is

not obtained, the system must be re-evaluated and the discrepancies must be

adjusted until compliance is regained. The final two steps in this process may

be considered to be the performance evaluation.

5 . 1 MONITORING PROCEDURES

The performance of the system may be monitored by obtaining data which can be

compared to system performance criteria (i.e., thermal, gaseous, and particulate

values), see table 3, or which can be compared to component performance criteria

(i.e., heat transfer rate across heating and cooling coils; filter efficiencies,

pressure drops, and loading capacities). For each factor to be compared, some instrumentation will be required to sense the values, and data acquisition

methods will be needed to store the data.

5.1.1 System Performance

The overall system performance should be evaluated in terms of environmental

and economic (including energy) factors. The environmental factors, including

thermal, gaseous and particulate data, may be obtained with instruments such as discrete samplers or continuous recorders. These devices may have local or remote sensing. The economic factors must be obtained with instruments such as log books and utility records.

The basic instrument currently used for monitoring temperature and humidity

conditions in archival storage facilities is the hygrothermograph. These are portable, continuous recording devices which require manual servicing and data

transposition for analysis. To date, direct periodic monitoring of the gaseous

or particulate concentrations within the facilities is seldom conducted. However, it was reported at the Workshop on Environmental Conditions for Archival

Storage that instrumentation has been used for monitoring SC>2 at the Library

of Congress.

32
Data for economic factors and energy consumption will probably be available in

forms that will not be readily useful for performance assessment. Thus, these

data will probably require transposition to formats that will be useful from an engineering aspect.

5.1.2 Component Performance

Within the overall system, component performance should be evaluated in terms

of efficiencies, capacities, and component costs (i.e., maintenance, operational,

replacement, etc.).

Performance of thermal control equipment is commonly monitored with portable

type instrumentation, or central monitoring systems. The techniques for obtaining these data are well-known, and have been recently given visibility through

the propagation of "energy auditor procedures." One such relatively thorough

procedure is cited in reference [84].

Performance of gaseous control devices is not as well-known. There are two

requirements for monitoring performance of either granular beds or wet-scrubbers.

1. Determination of the efficiency of the air cleaning unit (see figure 1):

e = -H ~-C

d . x 100% (4)

Cu

2. Determination of the total capacity of the air cleaner in terms of

quantity of contaminant that can be removed, or service life before

replacement, reactivation, or regeneration is required.

Instrumentation for continuous, real-time monitoring of acidic gases and vapors

is available, but somewhat expensive in the low ranges required for indoor air

quality monitoring. This problem also exists when the instrumentation is to be

used for "zero" effluent concentration or ”100 percent" efficiency of the air

cleaner. In the case of the granular bed, an alternative method of determining

the efficiency may be based on the use of Eqs. (2) and (3). The sample probes

are inserted at a bed depth where the efficiency is, say, 50 percent. The

detention time to that bed depth is then the half-life of the contaminant

vapor, and the efficiency at any other bed depth is:

e = (1 - 2"n

) x 100% (5)

where N is the number of half-lives. Using the half-life of 0.01 second in the

example cited earlier, the efficiency after 1 second detention time would be

(1 - 2 “100) x 100% = (100 - (8x 10“29)) percent, a value that is far too large

to be measured. However, the value does mean that there is only a small chance

for even one molecule to get through, so it is reasonable to call this value

100 percent efficiency.

Similar approaches for monitoring the efficiency of a wet-scrubber are theoretically applicable, but may be difficult in practice. One method might

33
be to measure effluent concentrations as a function of air flow rate through a scrubber, and extrapolate from high to low rates as the detention time

increases

The problem of determining the total capacity is very different for granular

beds and wet-scrubbers, because the concentrations in scrubber liquids are uniform, whereas in a granular bed, a mass transfer or reaction zone moves progressively through the bed in the direction of air flow.

If "capacity" is taken to mean the amount of contaminant that the air cleaner

can remove, then the action of the air cleaner is of prime concern. If "capacity" means service life of the air cleaner, then the contaminant concentration must

also be known.

In the first instance, the method of test is rather straightforward and can be

carried out by procedures analogous to ASTM retentivity tests [75]. In such a test, the adsorbent is first saturated with the challenge gas at high inlet

concentration (to accelerate the test), then subjected to a flow of clean air

to constant weight. Other approaches to determining the total capacity are also commonly used in working with adsorbents.

For determination of service life, it is essential to establish the timeweighted average concentration of the challenge gas. This can be done by

continous instrumental monitoring. Then the service-life may be determined as:

where

SL

^sat

Cave

x V

x V

Tsl = service life (time)

C sat = saturation concentration (mass/volume)

CaVe = average ambient concentration (mass/volume)

V = total volume of granular bed

V = volumetric air flow rate through the bed (volume/time)

( 6 )

Another approach to monitoring the capacity and service life is to use sequential

adsorbent samplers. This approach has recently been described by Turk, et al.

[85].

Performance of particulate filters should include the monitoring of the pressure

drop across barrier filter (i.e., the operating resistance), and monitoring of

the operating voltages of electronic air cleaners. Usually, such readings are adequate to ensure correct operation of filters.

5.2 ASSESSMENT PROCEDURES

The assessment of system performance is accomplished by analyzing the monitored

data and comparing the results in terms of the specified criteria. This

comparison may be done for system performance or component performance criteria.

34
5.2.1 System Performance

If comparisons between monitored and specified data are to be meaningful,

sufficient data must be obtained so that representative or mean values, and

standard deviations or ranges can be determined. It is also imperative that

reasonable specifications be used. For example if precise control of relative

humidity is required, then not only must the humidity control system be

responsive, but the temperature control system must also be responsive and

precise.

Also, for gaseous and particulate control, compatibility between the specified

methods of control and sensitivity of the monitoring instrumentation must be

assessed. It is possible to provide control conditions through open-loop

systems that will maintain concentrations below the least-count sensitivity of

the instrumentation [71].

5.2.2 Component Performance

As in the case for system performance assessment, care is required to assure

that the conditions of specified performance of a component are compatible with

those which existed during the period of monitoring. A need exists here for

assurance of dynamic stability.

5.3 EVALUATION PROCEDURE

Results of the component performance or system performance assessment should be

evaluated by a well-qualified person, with authority to rectify any "unacceptable" performances of the system as compared to its specified performance. Many

cases exist to support the position that this type of performance evaluation

can lead to environmentally acceptable and cost-effective operations.

35
6. BASELINE DATA FOR SELECTED FACILITIES USED FOR STORAGE OF PAPER- BASED

MATERIALS

Measurements were made by NBS of gaseous contaminants, temperature, and relative

humidity in the National Archives Building, the Madison Building of the Library

of Congress, and the East Wing of the National Gallery of Art. Air exchange

rate measurements indicating exchanges between the indoor air and outdoor air were also made by NBS at the National Archives Building. Temperature and relative humidity data from continuous recording hygrothermographs and printouts

from selected locations in the storage areas of the National Archives Building

were analyzed. The purpose of these measurements and analysis was to provide

baseline data for the National Archives Building on the range of control of

current air quality which could be useful in the upgrading of the environmental

conditioning system. Further, the air quality in the National Archives Building could be compared with the air quality in newer facilities having more modern types of environmental conditioning systems.

6.1

FACILITY AND TYPE OF ENVIRONMENTAL CONDITIONING SYSTEM

6.1.1 National Archives Building

The environmental conditioning systems were installed in the National Archives

Building in 1935 when the building was new. These systems have been modified

several times. Currently, about 10 percent outside air mixes with return air.

The mixed air passes through a prefilter and bag filter before passing a coil

where the air is heated, or cooled, or dehumidified. After passing the coil,

steam is used for humidification of the air before it reaches the supply fan.

The return air is filtered (bag filters) before it is mixed with the outside

air.

Nine air handling systems serve the National Archives Building (other than the

garage). Seven of the systems have two supply fans and one return fan each,

while each of the other two systems has one supply fan and one return fan.

According to National Archives and Records Service personnel, most of the air

handling systems serve both storage areas and offices. It was found by NBS

from air exchange measurements that air mixes rapidly throughout the building

(appendix C)

6.1.2 Madison Building of the Library of Congress

The Madison Building was completed and occupied in 1978. The HVAC system in

this building has 48 environmental zones. The zones are provided for interior

and building perimeter loads. All systems feeding the zones are high pressure,

1500 to 2000 Pa (6 to 8 in. H2 O) at fan discharge. All zones are provided with

20 percent make up air. Temperature is controlled at 20° C (68° F) and relative

humidity at 50 percent in the storage areas. Occupied areas are controlled at

comfort conditions.

Two diferent types of HVAC systems are used, one for storage areas and another

for occupied areas. The systems are straight draw through with steam humidification. For the storage areas, 100 percent of the air passes through chilled

36
water coils, whereas, for the occupied areas, the air is regulated so that only

a portion of the air passes through chilled water coils depending on comfort

conditions

.

The only pollution control in the storage areas is for SO2

. Outside air is

prefiltered before passing through packed beds, 0.5 m (19 in.) thick, of activated alumina (AI 2 O3 ) crystals coated with potassium permanganate. SO2 in the

air oxidizes to SO3 which is trapped as potassium sulfate in the catalyst or purifier beds. After the air passes through the catalyst beds it is mixed with

return air. The mixed air is then prefiltered before passing through bag

filters and washer units. Tap water is used in the washer units. The design

specifications limited SO2 to a maximum value of 5 ppb. Measurement by Architect of the Capitol personnel indicate that SO2 concentration is actually controlled to about 2 ppb. NBS measurements agree (appendix B). Architect of the

Capitol personnel did not measure NOx concentration. NBS found that N0X

concentrations tracked outdoor levels (figure 4, appendix B)

.

6.1.3 East Wing of the National Gallery of Art

The East Wing of the National Gallery was completed and occupied in 1978. Its

HVAC system is not zoned with regard to gallery and occupied space. The system

provides the building with 15 percent make up air. The outdoor air is passed

through two sets of bag filters, over a preheat coil, and then through an air

washer which is slightly alkaline. The air washer also humidifies the air.

The air is then mixed with filtered return air. The mixed air is supplied at

a temperature of 17-18°C (62-65°F). The gallery and occupied spaces are intended to be kept at 22°C (72°F) and 48 percent relative humidity. National

Gallery personnel have not attempted to monitor the level of gaseous

contaminants in the East Wing.

6.2 MEASUREMENTS AND DATA ANALYZED BY NBS

6.2.1 Sulfur Dioxide, Nitrogen Oxides, Ozone, Temperature, and Relative Humidity

Measurements of gaseous contaminant concentrations (SO2 , NOx, an^ O3 )

,

temperature, and humidity were made by NBS at the National Archives Building,

Madison Building of the Library of Congress, and the East Wing of the National

Gallery. The results of the measurements in the buildings and of the outdoor

air are presented in appendix B. The outdoor measurements were taken 2. 7-4.

3

km (1.7-2. 7 miles) from the three buildings by the Washington, D.C. government.

The nitrogen oxides concentration s) in the three buildings and at the

monitoring station show in general, two peaks each day corresponding to the

morning and evening rush hours. The nitrogen oxides measured in the three

buildings appeared to track the external atmospheric concentrations measured

by the Washington, D.C. government. The concentration of nitrogen oxide in

all three buildings, in general, greatly exceeded the criterion of 5 pg/m^

(2.5 ppb for NO2 ) given in section 3.6. It is difficult to determine how much

or if any nitrogen oxides are removed by the HVAC systems in these buildings.

The level of nitrogen oxides in general varied from day to day and was probably

affected by the weather. The HVAC system in the National Archives Building

37
essentially did not remove nitrogen oxides from the incoming air. While the

HVAC systems in the two other buildings may have removed a small part of the

atmospheric nitrogen oxides, the lower concentrations indoors than outdoors may

be explained equally well by low air exchange rates (air exchange rates were

not measured in these two buildings).

It appears that there is a correlation between the direction of the difference

between the measurements made in the Archives Buildings and those made by the

Washington, D.C. government, and the location of the air intake for the particular air handling system. The four air handling systems with penthouse or roof

air intakes had lower nitrogen oxides concentration than the outdoor concentration. Air handling systems with air intakes at ground level showed, in general,

higher concentration than the outdoor concentration. Nitrogen oxides concentration in the Madison Building and the East Wing of the National Gallery were, in

general, less than the outdoor concentration. The air intakes for these two

buildings were located at roof-top level.

Although the sulfur dioxide concentrations in eleven stack areas of the National

Archives Building were less than the outdoor concentration, most of these con- centrations exceeded the criterion of ^ 1 yg/m^ (0.4 ppb) given in section 3.6.

The sulfur dioxide concentrations in the other two buildings (one site was monitored in each building) were less than 0.5 ppb in the Madison Building and 1 ppb

in the East Wing of the National Gallery. Since these concentrations (0.5 and

1 ppb) were lower detectable limits of the instrumentation, it is not known if

the concentrations of SO 2 in these two buildings were less than the criterion

of 1 yg/m^ (0.4 ppb) given in section 3.6. Outdoor concentrations ranged

from 3 to 99 ppb.

No ozone was detected in any of the three buildings, while outdoor concentrations

were up to 21 ppb. This may be explained by the high reactivity of ozone. These measurements were made during the winter. Outdoor ozone concentrations

are higher in the summer. The criterion (section 3.6) limits ozone concentration to 25 yg/m^ (13 ppb).

The temperature and relative humidity measurements made by NBS during the

measurements of the gaseous pollutants indicate that the temperature in all

three buildings was, in general, controlled to within narrow limits, and the

relative humidity was controlled to within about 3.5 percent in the Madison

Building and the East Wing of the National Gallery (table 9, appendix B) . For

twelve of the thirteen locations monitored, the temperature ranged from 20.4 to

23.7°C (68.7 to 72.7°F). The relative humidity in the National Archives Building varied from 31 to 58 percent in the stack areas. The average (median) temperature was 22.2°C (72. °F) in the National Archives Building, 21.1°C (70.0°F)

in the Madison Building and 21.8°C (71.2°F) in the East Wing of the National

Gallery. Storage area temperatures in the National Archives Building measured

by NARS/GSA (section 6.2.3) were found to be similar to return air temperatures

measured by NBS (appendix C)

38
6.2.2 Air Exchange Rate Measurements in the National Archives Building

Air exchange measurements were carried out at the National Archives Building

under various combinations of temperature and wind speed. The purposes of the

measurements (described in detail in appendix C) were to:

(1) Determine the air exchange rate (as defined below) of the building

under normal operation of the heating, ventilating, and air

conditioning (HVAC) system, and with the outdoor air dampers closed.

(2) Determine the extent of air movement between archival storage areas

and other areas of the building.

(3) Assess the intrinsic air-tightness of the building envelope by means

of a fan pressurization test.

Air exchange rate, the rate at which outdoor air enters the condition space, is

defined as:

I = V/V (7)

where

:

I is the air exchange rate (air changes/hour, or h“l)

V is the volumetric air flow rate into or out of the building (m^/h)

V is the building volume (m^).

The average air exchange rate under normal operation of the HVAC system was

0.9 h

--*- for an average indoor-outdoor temperature difference of 11.3°C (20.3°F)

and an average wind speed of 2.7 m/ s (6.0 mph) . No clear dependence of air

exchange rate on temperature differences up to 17°C (31°F) or wind speeds up

to 5 m/ s (11 mph) was found.

With outdoor air dampers closed and fans operating, the average air exchange

rate was 1.2 h~l for an average indoor-outdoor temperature difference of 8.2°C

(14.8°F) and an average wind speed of 1.7 m/ s (3.8 mph). The air exchange

rates for temperature differences between 11°C (20°F) and 17°C (31°F) with the

dampers purposely closed, are similar to those under normal HVAC operation and

similar temperature differences. This may be because under normal operation of

the HVAC system, the dampers would be closed at these outdoor temperatures.

A test of interzone air movement showed that air migrates rapidly between non- stack and stack areas with fans operating normally.

The building could not be pressurized to an indoor-outdoor pressure difference

beyond 14 Pa (0.06 in. H2 O) . At this pressure difference the air exchange rate was 1.5 h”l.

39
A similar study of eight new GSA buildings in various parts of the United States

[86] shows that the National Archives Building is about twice as leaky as new office buildings, both under normal operation of the HVAC system and under

pressurization. Their air exchange rates under normal operation of the HVAC

systems vary from 0.2 to 0.6 h

-1 for outdoor temperatures of 4-10°C (39-50°F)

and wind speeds under 1.3 m/s (2.9 mph). Their air exchange rates at a pressure

difference of 14 Pa (0.06 in. ^0) were 0.5 to 0.9 h

6.2.3 Analysis of Temperature and Relative Humidity Data Recorded by the

National Archives and Record Service and the General Services

Administration

Stack temperature and relative humidity measurements, continuously recorded by

hygrothermographs , were provided by the National Archives and Records Service.

Printouts of stack temperature and relative humidity were provided by the

General Services Administration. The data on the printouts were recorded automatically from instrumentation installed in the stack areas. These data were analyzed for their variation over time, and uniformity among stack areas.

Printout data were recorded at 10:00 a.m. and 2:00 p.m. on May 6, 1983. The

continuously recorded data from the hygrothermographs began on May 3, 1983 and,

in general, continued for 6 days.

Comparisons were made of the temperature and relative humidity data from the

hygrothermograph charts and printouts for each of the 44 stack areas. The

temperature and relative humidity data are presented in table 8 along with the

number of days data were continuously recorded by hygrothermographs. There was

one hygrothermograph and from one to three temperature and relative humidity

sensors in each stack area. The locations of the instrumentation in the stack

areas were not reported.

From table 8, the temperature and relative humidity data can be summarized as follows:

a. Temperatures were consistent for both hygrothermograph charts and

printout data. The median temperature was 22°C (72°F) for the hygrothermograh readings and 23°F (73°F) for the printout data. The

temperature range was 19 to 26°C (66 to 78°F).

b. For 21 of 27 stack locations for which comparisons could be made,

relative humidity was consistent for hygrothermograph charts and

printout data. The median relative humidity was 40 percent for the

hygrothermograph charts, and 39 percent for the printout data. The

range in relative humidity was 28 to 54 percent for the hygrothermograph charts and 21 to 50 percent for the printout data.

c. For the hygrothermograph data, there was a difference of 3°C (6°F)

or less between the high and low readings for 39 of 41 stack areas.

d. For the hygrothermograph data, in 37 of 41 stack areas for which data were available there was a difference of 10 percent or more between

40
Table 8. Temperature and Relative Humidity Data

Hygro thermograph Data*/ Printout Data

Area TemperatureMay 6 Temperature

Range Relative HumidityMay 6

Relative Humidity

Range Number

of Days^/

Temperature

May 6 Relative Humidity

May 6

10 a.m. °P

2 p.m. •f

May 3-9

•f

10 a.m.

%

2 p.m.

Z May 3 - 9

Z

10 a.m.

° F

2 p.m.

° F

10 a.m. 2 Z p.m.

Z

5E4 71 72 70 - 74 36 35 35 - 54 6 72 72 39 39 5E3 72 72 70 - 74 37 37 37 - 49 6 73 73 33 33 5E3 — — — — — — — 73 73 31 31 6E3 71 72 70 - 74 34 32 32 - 44 5 73 73 31 30 6E3 — — — — — — — 71 71 21 21 21E3 67 67 62 - 68 44 43 41 - 92 6 — — — —

21 E4 66 66 64 - 68 54 50 51 - 70 6 — — — —

21W4 73 73 72 - 76 37 37 37 - 46 5 74 74 36 36 21W4 — — — — — — — 74 74 42 42

21W3 70 70 68 - 73 28 29 29 - 37 6 — — 38 39 19E1 74 74 73 - 75 31 32 31 - 48 6 — — — —

19 E2 77 78 74 - 80 31 33 32 - 41 6 — — — —

19E3 67 67 60 - 70 45 44 32 - 75 5 — — — —

18E1 68 68 67 - 67 38 37 36 - 53 3 — — — —

18E3 69 70 68 - 72 43 42 42 - 55 3 — — — —

18E2A 67 67 66 - 70 37 37 36 - 48 5 — — — —

18W2A 69 70 70 - 72 35 35 34 - 48 6 — — — —

18 E4 72 72 71 - 73 41 40 42 - 54 4 — — — —

14E3 72 72 72 - 72 49 45 45 - 68 6 70 70 36 36 14E3 — — — — — — — 69 70 — —

13E3 — — 68 - 72 — — 58 - 79 3 72 72 40 40 13E3 — — — — — — — 70 70 39 39 12E1 72 72 68 - 72 40 40 40 - 68 4 70 70 35 37 13E4 72 72 70 - 73 38 38 40 - 51 4 73 73 35 34 11E2 71 72 71 - 74 41 40 40 - 58 3 69 69 40 40

11E2 — — — — — — — 69 69 40 41 10E2 — — 47 - 49 42 42 42 - 63 6 68 68 41 42

10E2 — — — — — — — 70 70 40 40 8E1 — — — — — — — 70 70 40 40

7E1 76 78 70 - 78 40 40 40 - 54 6 74 74 41 41 2E2 66 67 63 - 67 40 40 40 - 60 6 70 70 46 45 2E2 — — — — — — — 68 68 44 45

3E2 69 70 68 - 70 46 46 46 - 69 4 67 67 32 32 3E2 — — — — — —

4/13/

69 69 40 41 3E2B 72 72 69 - 72 — — 52 - 66 — — — —

3E2A 73 73 72 - 78 38 39 36 - 50 4 74 74 — —

3E2A — — — — — — — 77 77 40 41 G13 75 76 71 - 77 32 38 32 - 58 4 75 77 38 46 2W1 74 75 70 - 75 40 40 32 - 50 6 75 76 37 39 2W1 — — — — — — — 75 75 39 41

19W3 72 73 72 - 78 30 30 30 - 50 5 72 72 32 33 19W3 — — — — — — — 74 74 -1 -1 18W1 — — — — — — — 75 76 44 41 18W1 — — — — — — — 75 77 38 35

18 W2 74 — 72 - 75 37 — 32 - 47 3 74 75 41 43 15W3 76 76 75 - 80 34 34 34 - 49 4 73 73 30 31 15W3 — — — — — — — 74 74 33 34 13W3 74 75 70 - 76 26 28 25 - 46 6 74 74 29 30 13W3 — — — — — — — 75 75 30 33

11W1 — — — — — — — 73 73 41 41 11W4 74 74 73 - 76 45 42 40 - 54 7 73 73 36 37 11W2A 72 72 70 - 73 42 42 40 - 56 4 70 70 23 25 11W2 68 69 67 - 70 46 45 37 - 54 6 69 69 46 46 11W2 — — — — — — — 69 69 47 48 10W2 70 71 68 - 71 50 50 42 - 58 6 68 68 50 50 10W2 — — — — — — — 68 68 50 50 8W2 73 74 71 - 75 46 47 42 - 54 4 69 69 47 49 8W2 — — — — — — — 68 68 49 50 8W3 72 73 72 - 77 34 34 33 - 50 5 75 74 33 34 8W3 — — — — — — — 75 75 35 36 5W2 68 68 64 - 68 46 48 39 - 58 6 68 68 49 50 5W2 — — — — — — — 68 68 49 50 4W1 74 74 72 - 74 37 44 37 - 54 4 74 75 38 40

1W1 — — 74 - 76 — — 30 - 36 2 75 76 38 39 1W1 — — — — — — — 77 77 34 37 1U1 — — — — — — — 75 76 35 37

Temperature and relative humidity data continuously recorded beginning about 10 a.ra. on May 3.

2/ Number of days that temperature and relative humidity were continuously recorded on charts.

2/ Temperature recorded for 4 days and relative humidity recorded for l day.

41
the high and low values of relative humidity. In 29 stack areas this

difference was 14 percent or greater. The maximum range of relative

humidity was 29-92 percent.

e. The temperature in the stack areas was controlled within reasonable

limits, however, there was little or no control of relative humidity.

42
7 . SUMMARY

To aid the National Archives and Records Service and the General Administration

in improving environmental conditions for storage of paper-based archival

records at the National Archives Building, criteria are proposed for levels of

environmental control and baseline data are provided on the present range of

control of air quality in this building. The proposed criteria (table 3, sec- tion 3.6) are based on available information on the preservation of paper-based

materials and the capabilities of environmental conditioning systems. Recommendations from the January 19-20, 1983, National Bureau of Standards Workshop

on Environmental Conditions for Archival Storage are included in the proposed

criteria. Other design parameters are addressed and recommendations made

regarding factors to consider in the design of archival storage facilities.

Measurements were made by NBS of temperature, relative humidity, and gaseous

air pollutant concentrations at the National Archives Building, and for comparison, at the Madison Building of the Library of Congress and the East Wing of

the National Gallery of Art. These two buildings have modern (1978) environmental conditioning systems. Air exchange rate measurements under various

conditions were taken at the National Archives Building to test the performance

of the HVAC system, to measure air leakage into and out of the building, and

to measure air mixing between storage and other areas of the building.

The January 19-20, 1983, National Bureau of Standards Workshop on Environmental

Conditions for Archival Storage divided storage conditions into three categories

on the basis of length of time of storage and accessibility of storage materials

to the public. Storage temperature and relative humidity given in the proposed

criteria (table 3, section 3.6) were recommended to be successively lowered as required accessibility decreased. In all three cases, temperature and relative

humidity should be maintained nearly constant at their recommended levels. The

3 (2.5

A review of literature (section 2) describes the damage that may be caused by

temperature, relative humidity, and air pollutants to paper-based records, and

gives examples of air quality criteria used by various libraries and musuems.

Concentrations of SC>2 in the National Archives Building, where SC>2 is not

controlled, were much greater than 1 yg/m^, while concentrations in the other

two buildings were about the same or possibly lower than this recommended limit.

SO2 concentrations in the Madison Building and East Wing of the National Gallery

of Art did not exceed the lower detectable limits of the instrumentation of

1 yg/m^ (0.5 ppb) and 2 yg/m^ (1 ppb) respectively. Nitrogen oxides concen- trations in these two buildings were lower than in the National Archives Building, but frequently exceeded 5 yg/m . Concentrations of N0X

in all three

buildings tracked outdoor concentrations. N0 X concentrations in the National

Archives Building for those air handling systems having roof air intakes, were

lower than the measured outdoor concentrations at ground level reported by the

Washington, D.C. Government. With air intakes at ground level, indoor N0 X

recommended air pollutant limits were 1 yg/m J (0.4 ppb) for SO 2

, 5 yg/i

ppb for NO

2

) for N0X , 25 yg/m 3 (13 ppb) for O

3

, 4.5 ^/g/m3 for CO2, and

75 yg/m^ for total suspended particulates (table 3, section 3.6).

43
concentrations were higher than outdoor concentrations. Ozone was not detected

in any of the three buildings (appendix B)

Temperature was well-controlled in all three buildings. The median temperature

was 22-23°C (72-73°F) in the National Archives Buidling (section 6.2.3). Relative humidity was well-controlled in the Madison Building and the East Wing of

the National Gallery. It was not controlled in most of the storage areas in

the National Archives Building, where it ranged from 29 to 92 percent (section

6.2.3)

Air exchange rates between indoor and outdoor air in the National Archives

Building were found to be about 0.9 air changes per hour at an average indooroutdoor temperature difference of 11. 3° C (52.3° F) and average wind speed of

2.7 m/s (6.0 mph) with the HVAC system operating. An air exchange rate of 1.5

changes per hour was found at an indoor-outdoor pressure difference of 14 Pa

(0.06 in. H2 O) . The air exchange rates under both natural and pressurized

conditions were about twice the air exchange rate for newer General Services

Administration office buildings. The tests showed that air in storage areas

in the National Archives Building is immediately and thoroughly mixed with air

in office and public use areas (appendix C)

44
8.

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45
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29. Sclawy, Adrian C, "The Effect Varying Relative Humidity Conditions on the

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35. Langwell, W. H. , "How Does Air Pollution Affect Books and Paper?" Address

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37. Smith, R. D. , "The Preservation of Leather Bookbindings from Sulfuric Acid

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38. Kimberly, A. E. and Scribner, B. W. , "Summary Report of Standards Research

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39. Hudson, F. Lyth; R. L. Grant; and J. A. Hockey, "The Pick-Up of Sulfur

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40. Hudson, F. L. and Milner, W. D., "The Use of Radioactive Sulfur to Study

the Pick-Up of Sulfur Dioxide by Paper," Paper Technology 2, 155-161,

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41. Barrow, W. J., "Migration of Impurities in Paper," Archivum 3, 105-108,

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42. Hudson, F. Lyth, and W. D. Milner, "Atmospheric Sulphur and the Durability

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47
43. Langwell, W. H. , "Sulfur Dioxide Pollution of the Atmosphere," Society of

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44. Stern, A. C. , "Air Pollution," 3 Volumes, Academic Press, Inc., New York,

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45. Greathouse, G. A. and Wessel, C. J., Eds., "Deterioration of Materials,

Causes and Preventive Techniques," Reinhold, New York, 1954.

46. Rogers, J. S. and Beebe, C. W. , "Leather Bookbindings, How to Preserve

Them," Booklet No. 398, U.S. Department of Agriculture, Washington, D.C.,

1956.

47. Bogaty, Herman, Campbell, Kenneth S., and Appel, William D. , "The Oxidation

of Cellulose by Ozone in Small Concentrations," Textile Research Journal , Vol. 22, February 1952, pp. 81-83.

48. Swanton, John R. Jr., "Field Study of Air Quality in Air-Conditioned

Spaces," ASHRAE Transactions , 77 (Part 1), 124-139, 1971.

49. Haagen-Smit, A. J., "The Chemistry of Atmospheric Pollution," Proceedings

of the London Conference on Museum Climatology , London IIC, 89-94, 1968.

50. ASHRAE Handbook, Fundamentals Volume, 1981, Chapter 11, American Society

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51. ASHRAE Standard 52-76, Air Cleaning Devices Used in General Ventilation

for Removing Particulate Matter , Method of Testing, Atlanta, 1976.

52. ASHRAE Handbook and Product Directory, Equipment Volume, 1979, American

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Atlanta, 1979.

53. ASHRAE Handbook, Applications Volume, 1982, American Society of Heating,

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54. Thomson, Garry, "The Museum Environment," (In Association with the

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Butterworths , London, 1978.

55. Federal Archives and Records Center Facility Standards, Revised January

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56. Colle, R. , R. J. Rubin, L . I. Knab, and J. M. R. Hutchinson, "Radon

Transport Through and Exhalation from Building Materials," National

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48
57. Toishi, K. Kenjo, and R. Ishikawa, "Alkaline and Acidic Particles in

the Air within Concrete Buildings," Science for Conservation , 8:61-70,

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58. Indoor Pollutants , Report by the Committee on Indoor Pollutants, National

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59. Wadden, R. A., and P. A. Scheff, Indoor Air Pollution, John Wiley and

Sons, N. Y., 1983, pp. 62-68.

60. Jarke, F. H. , "Organic Contaminants in Indoor Air and their Relation to

Outdoor Contaminants," Final Report of ASHRAE Research Project 183,

December 1979.

61. Smart, R. C. , The Technology of Industrial and Explosion Hazards , Volume 2,

Chapman and Hall, London, 1947, pp. 64-68.

62. Woods, J. E., "Sources of Indoor Contaminants," ASHRAE Trans. , (In Press)

1983.

63. Clark, R. P., and R. N. Cox, "The Generation of Aerosols from the Human

Body," In Airborne Transmission and Airborne Infection , J. F. P. Hers

and K. C. Winkler, eds. New York, John Wiley and Sons, Inc., 1973,

pp. 413-426.

64. Wang, T. C. , "A Study of Bioeffluents in a College Classroom," ASHRAE

Trans

.

, 81 (Part 1): 32-44, 1975.

65. Jacobson, A. R. and S. C. Morris., "The Primary Air Pollutants - Viable

Particulates: Their Occurrence, Sources, and Effects," In: Air Pollution , Third Edition, Volume I, Air Pollutants, Their Transformation and

Transport, Academic Press, NY, 1976, pp. 169-196.

66. I.E.S. Handbook , 1981 Application Volume, Illuminating Engineering Society,

Waverly Press, 1981, pp. 19-31 to 19-33.

67. National Oceanic and Atmospheric Administration, "Climatological Data:

(local area)", Volumes 93 and 94, National Climatic Data Center, Asheville,

NC, 1982 and 1983.

68. ASHRAE Handbook, Fundamentals Volume, 1981, Chapters 11, 24, and 28,

American Society of Heating, Refrigerating and Air-Conditioning Engineers,

Inc., Atlanta 1981.

69. ASHRAE Standard 62-1981, Ventilation for Acceptable Indoor Air Quality , Atlanta , 1981.

70. Montag, G. M. , "Revision of Economic Models I and II, and Development of

Model III: Supplemental Sections for Manual of Procedures for Authorized

Class A Energy Auditors in Iowa (Second Edition)," Volume 4 of Final

49
Report, Development of Energy Management program for Buildings in Iowa,

Fourth year, Iowa State University 82469, 1982.

71. Woods, J. E. , E. A. B. Malonado, and G. L. Reynolds, "Safe and Energy

Efficient Control Strategies for Indoor Air Quality," Presented at the

Annual Meeting of American Association for Advancement of Sciences,

Toronto, Canada, 1981, Iowa State University, Report ERI-BEUL-81-01

72. ASHRAE Handbook, Fundamentals Volume, 1981, Chapter 32, American Society

of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta

1981.

73. Workshop on Indoor Air Quality Research Needs, Interagency Research

Group on Indoor Air Quality, Interagency Energy/Environment R&D Program

Report, United States Department of Energy, United States Environmental

Protection Agency, April 1981.

74. Turk, A., "Tracer Gas Nondestructive Testing of Activated Carbon Cells",

Materials Research and Standards , 9:24-26, 1969.

75. ASTM Standard D-3467 , Standard Test Method for Carbon Tetrachloride

Activity of Activated Carbon , American Society for Testing Materials,

Philadelphia, PA, 1976.

76. McShane, H. , "Low Cost Filters Can Cost Too Much", Actual Specifying

Engineer , May 1975.

77. "Instruction Manual for the Installation, Operation, and Maintenance of

Penetrometer Filter Testing, DOP , Q107," U.S. Army, Edgewood Arsenal

Document No. 136-300-175A.

78. Hirasawa, K. and T. Kawamata, "A Study on the Necessity of HEPA Filter

for Removing Particles of 0.1 m," Presented at the 6th Annual International

Symposium on Contamination Control, Tokyo, 1982, Japan Air Cleaning

Association, 1982.

79. Hayakawa, I., Shi. Fugii, and K. Iwasawa, "Filter Efficiency for Submicron

Particles by Condensation Nucleus Counter," Presented at the 6th Annual

International Symposium on Contamination Control, Tokyo, 1982, Japan Air

Cleaning Association, 1982.

80. Standard 680 - "Standard of Air Filter Equipment," Air Conditioning and

Refrigeration Institute, Arlington, Va.

81. Emi, H. , C. Kanaoka, and T. Ishiguro, "Collection Performance of High

Efficiency Air Filters," Presented at the 6th Annual International

Symposium on Contamination Control, Tokyo, 1982, Japan Air Cleaning

Association, 1982.

50
82. Qshige, K. and T. Kawamata, "High Efficiency Filtration Method of HEPA

Filter with Ion Discharging System," Presented at the 6th Annual International Symposium on Contamination Control, Tokyo, 1982, Japan Air Cleaning

Association, 1982.

83. Masuda, S. and N. Sugita, "Electrostatically Augmented Air Filter for

Producing Ultra-Clean Air and its Collection Performance," Presented at

the 6th Annual International Symposium on Contamination Control, Tokyo,

1982, Japan Air Cleaning Association, 1982.

84 . Manual of Procedures for Authorized Class A Energy Auditors in Iowa , Second Edition, ISU-ERI-Ames , Report No. 79163, Iowa State University,

Ames, Iowa, 1979.

85. Turk, A., L. Oti, E. Steinberg, and T. Bergstein, "Assessing the

Performance of Activated Carbon in the Indoor Environment," Paper

presented at the 74th Annual Meeting of Air Pollution Control Association , Philadelphia, PA, June 1981 .

86. Grot, R. A., Y-M. L. Chang, A. K. Persily, and J. B. Fang, "Interim Report

on NBS Thermal Integrity Diagnostic Tests in Eight GSA Federal Office

Buildings," NBSIR 83-2768, September 1983.

51

APPENDIX A. LIST OF WORKSHOP PARTICIPANTS

WORKSHOP ON ENVIRONMENTAL CONDITIONS

FOR ARCHIVAL RECORDS STORAGE

January 19-20, 1983

NATIONAL BUREAU OF STANDARDS

Warren B. Johnson

Lennox Industries

P.O. Box 400450

Dallas, Texas 75240

Dr. Robert E. McComb

Room LM-G38

Library of Congress

Washington, D.C. 20540

William P. Lull

Syska and Hennessy, Inc.

11 West 42nd St.

New York, New York 10036

Charles A. Madson

824 Park Avenue

River Forest, Illinois 60305

Dr. Amos Turk

Professor, Department of Chemistry

The City College of the City

University of New York

New York, New York 10031

Karl L. Westlin

6807 Cooper Chapel Road

Louisville, Kentucky 40229

Dr. James E. Woods

Department of Mechanical Engineering

Iowa State University

Ames, Iowa 50011

Paul N. Banks

Conservator and Preservation

Administrator Programs

School of Library Service

516 Butler Library

Columbia University

New York, New York 10027

Ms. Shelley Fletcher

Head, Paper Conservation

National Gallery of Art

Washington, D.C. 20565

Tim Padfield

Conservation Analytical Laboratory

Room AB 070 AHB

Smithsonian Institution

Washington, D.C. 20560

Te. 357-2444

Dr. Carl J. Wessel

5014 Park Place

Bethesda, Maryland 20816

William K. Wilson

1401 Kurtz Road

McLean, Virginia 22101

Phillips Rogers

National Archives & Records Service

Washington, D.C.

Maxwell K. Foster

Project Officer

General Services

National Capital

7th & D Streets,

Washington, D.C.

Robert Shreeve

General Services

National Capitol

7th & D Streets,

Washington, D.C.

20408

Administration

Region

S.W.

20407

Administration

Region

S.W.

20407

A-l
Thomas K. Faison

National Bureau of Standards

Center for Building Technology

Building 226, Room B306

Washington, D.C. 20234

Robert G. Mathey

National Bureau of Standards

Center for Building Technology

Building 226, Room B348

Washington, D.C. 20234

Dr. Preston E. McNall

National Bureau of Standards

Center for Building Technology

Building 226, Room B218

Washington, D.C. 20234

Dr. Samuel Silberstein

National Bureau of Standards

Center for Building Technology

Building 226, Room A313

Washington, D.C. 20234

Randall Biallas

National Park Service

Ernest E. Hughes

Gas & Particulate Science Division

Center for Analytical Chemistry

National Bureau of Standards

Washington, D.C. 20234

Lawrence Klock

National Park Service

Independence NHP

313 E. Walnut Street

Philadelphia, Pennsylvania 19106

Vitaly Sazonov

General Services Administration

National Capital Region

7th & D Streets, S.W.

Washington, D.C. 20407

Alan Calmes

Preservation Officer

National Archives and Records

Service

Washington, D.C. 20408

James Megronigle

National Archives and Records

Service

Washington, D.C. 20408

A-2


APPENDIX B.

NBSIR 83-2767

Measurement of the Concentration of

Sulfur Dioxide, Nitrogen Oxides, and

Ozone in the National Archives Building

November 1983

U S DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

B-1

NBSIR 83-2767

MEASUREMENT OF THE CONCENTRATION OF

SULFUR DIOXIDE, NITROGEN OXIDES, AND

OZONE IN THE NATIONAL ARCHIVES BUILDING

E. E. Hughes and R. Myers

Gas and Particulate Science Division

Center for Analytical Chemistry

National Bureau of Standards

Washington, D.C. 20234

November 1 983

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

TABLE OF CONTENTS

Page

Introduction 1 Experimental Approach 1 Sample Sites 2 Data Collection — Sulfur Dioxide and Nitrogen Oxides 2 Data Collection — Ozone 3

Calibration 3

Results — Oxides of Nitrogen 4

Results — Sulfur Dioxide 5

Results — Ozone 6

Other Measurements 6

Conclusions 7 Acknowledgment 7 Attachment: Report of the 1977 study at the National Archives building .... 18

LIST OF TABLES

Table No. Page

1 Sampling Location and Dates at The National Archives 2

2 Relationship Between Air Inlet and Relative Concentration of

Nitrogen Oxides 5

3 Difference of Sulfur Dioxide in the Stack Areas Compared to

Incoming Air 6

4 Hourly Average Concentrations of Nitrogen Oxides Measured at National

Archives, Madison Building and East Wing 8

5 Hourly Average Concentrations of Nitrogen Oxides Measured by D.C.

Government at 24th and L Streets, N.W 10

6 Hourly Average Concentrations of Sulfur Dioxide Measured at the

National Archives 12

7 Hourly Average Concentrations of Sulfur Dioxide Measured by D.C.

Government at 24th and L Streets, N.W 13

8 Ozone Measured at 24th and L Streets, N.W. by the District of Columbia . . 14

9 Summary of Temperature and Relative Humidity Measurements 15

FIGURES

The figures consist of five figures that are plots of the concentration of oxides

of nitrogen measured at different locations. These begin on page 15.

Introduction

The ubiquitous nature of certain gaseous substances in the atmosphere assures us that if these substances exist in appreciable quantities outside of a building they

will surely exist to an equal or lesser degree within the building unless some sort

of barrier is interposed between the interior and exterior of the building. A brief

study performed in 1977 at the National Archives indicated that both ozone and

nitrogen oxides passed freely into the building through the ventilating system, but

that sulfur dioxide was reduced in concentration compared to that expected from the

outside air. The study described in this report was performed in a similar manner,

but with several major differences in scope and with a somewhat different outcome.

[The original report is appended.]

In the 1977 National Archives study, ozone, sulfur dioxide and nitrogen oxide

were measured in only one area. In the present study, measurements were made at

eleven locations, each supplied by a different supply fan. 1 The conclusion reached

in 1977 regarding the reduction in sulfur dioxide could not be confirmed by the

present study, although the finding regarding nitrogen oxide was essentially the same.

In addition, measurements were made at single sites in the Madison Building of

the Library of Congress and in the library area of the East Wing of the National

Gallery of Art. These measurements were intended to offer a comparison between an older ventilating system (circa 1932) and newer systems designed specifically for

buildings intended for archival storage.

Experimental Approach

The measurements had a two-fold purpose: first, to determine whether or not the

! ventilating system modified the quality of atmospheric air during passage into the

building, and second, to measure the concentration of each of the three species of

interest in air passing into the stack (archival storage) areas of the building. The

second purpose can be fulfilled by interior measurements using calibrated instruments.

The first could be satisfied by simultaneous measurments of the air entering the

ventilating system and air exiting the system into the stacks. However, such simultaneous measurements would require duplicate instrumentation, considerably more time

at each location, and substantially increased costs. In any case, it was concluded

in the 1977 National Archives study that this approach was not feasible because of

the geometry of the building and the inaccessibility of the intakes of many of the

systems. It was concluded, nonetheless, that observations of the pattern of concentration changes in the ambient atmosphere of Washington, D.C. and the pattern of

changes within the building would yield sufficient information regarding the current

capability of the system for removing portions of the pollutant gases of interest.

Fortunately, the District of Columbia continuously monitors these gases, and the data

from such measurements were made readily available for this study.

The supply air entering each sampling site was measured for a minimum of 24

hours, but in most cases for at least 48 hours. Nitrogen oxides as NOx (N02 + NO) and

sulfur dioxide were measured continuously, while ozone was measured for several short

periods of time during each day of sampling. Calibrations were performed at the

beginning and end of each sampling period, and once every 24 hours during that period.

Permeation tubes were used to calibrate the sulfur dioxide analyzer, while permeation

tubes and an analyzed mixture of nitric oxide in nitrogen were used to calibrate the

nitrogen oxide analyzer.

x Nine consecutively numbered heating and air conditioning systems serve the National

Archives Building. Each, with the exception of systems 2 and 4, is composed of two

supply fans and one return fan. Systems 2 and 4 each have one supply fan and one

return fan.

1
The ozone instrument was operated as an "absolute" instrument whose measurement

characteristics were predetermi ned at NBS. It was only necessary to measure

instrument temperature and barometric pressure to calculate the ozone content of the

sampled air.

During each analytical period several measurements of barometric pressure,

temperature, and relative humidity were made. These measurements were made near the

analytical site, away from the direct flow of supply air, but close enough to be

reasonably sure that the sampled air originated in the particular ventilating system.

Temperature and humidity measurements are summarized in Table 9.

Sample Sites

The sample sites are listed in Table 2 in the order in which the measurements were

made. The information regarding stack areas and the identification of the supply fans

and ventilating system supplying each area was furnished by the National Archives.

The sample probe was located directly in the path of the air entering the area from

the ventilating system. In most cases, the probe was moved at least once during

each sampling period to an area away from the inlet vent.

The sample site in the Madison Building was in the Manuscript Preparation Section

adjacent to a doorway marked LM123. The sample inlet probe was located about 2.5

meters above floor level.

Table 1. Sampling Location and Dates at The National Archives.

Sequence Sampling Site Supply Fan Sampling Period

1 3E3 9A Dec. 1-3, 1982

2 1 E2A 5B Dec. 3-7, 1982

3 9E1 7A Dec. 7-9, 1982

4 7E4 9B Dec. 9-10, 1982

5 10E2 7B Dec. 12-17, 1982

6 9W4 8B Dec. 28-30, 1982

7 9W3 8A Jan. 3-5, 1983

8 9W2 6A Jan. 5-7, 1983

9 19W2 6B Jan. 11-13, 1983

10 17W1A IB Jan. 13-14, 1983

11 3W2B 5A Jan. 19-27, 1983

Sampling in the East Wing of the National Gallery of Art was done in stack level

"B" in the library area. The probe was located at ceiling level adjacent to an air

inlet duct.

Data Collection — Sulfur Dioxide and Nitrogen Oxides

The signals generated by the sulfur dioxide and the nitrogen oxides were continuously recorded on a strip chart recorder. The "zero" for each instrument was established during daily calibration periods by analyzing "zero air" produced by a clean air generator. The signal produced by the sampled air was adjusted for zero

and converted to a concentration using one of the calibration factors determined

2
during the daily calibration. Several points on each chart were read during each

hourly period and the final concentrations are expressed as hourly averages. '11 of

the hourly averages for sulfur dioxide and nitrogen oxide for each sample site are included in Tables 4 and 6. Tables 5, 7 and 8 include the hourly averages of nitrogen

oxides, sulfur dioxide and ozone measured by the Air Monitoring Division of the Bureau

of Air and Water Quality of the District of Columbia.

Data Collection — Ozone

Ozone measurements at the first few sites were made at approximately 30 second

intervals for periods of up to 16 hours. As the study progressed, it became obvious

that little or no ozone was present in the building and the sample periods were shortened in length. Initially, the data were averaged over the sampling period or

for one-hour intervals (whichever was larger), and the averages were compared to the

averages from "zero air".

Cal i brat ion

The accuracy required for a study such as the one described in this report is not

great. An uncertainty in the measurements of 10% will still allow reasonable conclusions to be drawn. It was possible, therefore, to devise a calibration scheme that

was adequate relative to the accuracy needed, and which also lay within the bounds set

by the requirements for portability, availability, and economy. As previously

mentioned, permeation tubes were used as cal i brants for sulfur dioxide and nitrogen

dioxide, while a gas mixture of nitric oxide in nitrogen was used to calibrate for

nitric oxide. The uncertainty of the gas mixture was ±2 percent relative, and was established by analysis against primary gravimetric standards.

The uncertainty of composition of a calibration mixture generated by permeation

tubes depends on the uncertainty of the permeation rate of the tube and the uncer- tainty in the flow of diluent air passing over the tube. The flow of air was measured

with a calibrated rotameter. The permeation rate at the time of each calibration was estimated from the measured temperature dependence of the rate, and the temperature of

storage just before calibration. It is difficult however to assign uncertainties to

the various parameters affecting the concentration; therefore, the uncertainties of

the concentrations of the calibration mixture generated with permeation tubes are estimated from measured instrument responses. This assumes that the instrument is

stable and that the day-to-day variations are due to differences between the calculated and actual concentrations. The observed variation of the sensitivity (signal/

concentration) for both sulfur dioxide and nitrogen oxides analyzers calibrated with

permeation tubes was about ±10 percent relative over the more than two months course

of the measurements. It should be noted that the ±10 percent variation affects the

absolute measurement and not the relative measurements. That is, variations during

an analysis can be defined with much greater certainty than can the absolute

concentration at any time.

The calibration mixture uncertainty affects the measurement of sulfur dioxide

much more than the oxides of nitrogen. This is because the primary calibration of

the oxides of nitrogen depended on a stable gas mixture, with the permeation tubes

used as an additional confirmation of instrument sensitivity (and to assure that the

measured NOx reflected the true sum of NO + N02 ). Consequently, the maximum uncer- tainty of the measurement of oxide of nitrogen does not exceed ±5 percent relative.

The ozone instrument is essentially an absolute photometer. The absorption

path length and the absorption coefficient for ozone are both known with a small

uncertainty. It is only necessary to measure the temperature and pressure of the

sample in the absorption cell to allow a calculation of the ozone concentration.

However, because little or no ozone was measured at any of the sampling sites, it was

3
really necessary only to be sure that the instrument was on and functioning during

each sampling period.

Results - Oxides of Nitrogen

The principal source of oxides of nitrogen in Washington, D.C. is the internal

combustion engine of motorized vehicles. Since these oxides are distributed over the

entire urban area, it is expected that patterns of concentration would be similar in

different parts of the city. This we found to be true when comparing the concentrations measured by the District of Columbia at 24th and L Streets, N.W., with concen- trations measured at the National Archives, the Madison Building of the Library of

Congress, and the East Wing of the National Gallery of Art (Tables 4 and 5). In

general, the diurnal pattern of nitrogen oxide at any location shows two peaks

corresponding to the morning and evening rush-hours. The minimum concentration

occurs between 2:00 and 5:00 a.m. During daylight hours between the morning and

evening rush there is another period of decreased concentration. However, this

concentration is usually higher than the early morning minimum. Figure 1 represents

measurements made over a 48-hour period at site 9W2 in the National Archives and

measurements made during the same period at 24th and L, N.W. While the magnitude of

the peaks are different, the peaks occur at the same times and, more importantly, the

periods of reduced traffic (and presumably more diffuse sources) show surprisingly

good coincidence. The differences in peak heights are most likely due to different

physical locations of the sample probes and local variation in traffic density. The

24th and L probe is suspended at a height of about 8 meters above L Street. The

sample probe at the Archives was located inside the building and was sampling air

obtained from rooftop level.

Figure 2 represents similar measurements made at site 9W4, and Figure 3 represents

measurements made at site 9E1. Site 9W4 gave results a little more typical than 9W2,

only in that the coincidence of the two separate curves was somewhat less ideal. The

measurements at 9E1 illustrate a situation which is not readily explained. Beginning

around 1700 of Day 1 very unexpectedly high concentrations were recorded, and the

signal exceeded the range of the recorder at the Archives' site early in the evening.

The interesting point is that the concentration within the Archives is precisely

tracking the external atmospheric concentration.

In several cases, the concentration of nitrogen oxides within the Archives

exceeded that measured by the District of Columbia throughout the entire sampling

interval or during a substantial part of the interval. The differences between the

District of Columbia measurements and the measurements in the Archives can be correlated with the location of the intake for a particular system. If the results are examined carefully, the two systems with four attic or roof intakes have lower

nitrogen oxide contents than the measurements made simultaneously by the District of

Columbia. Those systems with intakes at ground level show higher values than the

simultaneous District of Columbia measurements, with few exceptions. Even the

exceptions, 9E1 and 10E2, show the correlation during part of the sampling period.

This is summarized in Table 2.

The oxides of nitrogen measured at the Madison Building of the Library of

Congress and at the East Wing of the National Gallery of Art track the concentration

measured by the District of Columbia in a similar manner to the National Archives

(Figs. 4 and 5). Perhaps because the ventilating system intakes for these two

buildings are located at rooftop level, the measurements inside are generally less

than the measurements at 24th and L, N.W.

4
Table 2. Relationship Between

Oxides.

Air Inlet and Relative Concentration of Nitrogen

Supply

Fan

Stack Intake Location Archives Relative to D.C.

8A 9W3 Attic Less

8B 9W4 II II

9A 3E3 II II

9B 7E4 II II

IB 17W1A Ground Greater

5A 3W2B II II

5B 1 E2A II II

6A 9W2 II II

6B 19W2 II II

7A 9E1 II Inconclusive

7B 10E2 II II

Results — Sulfur Dioxide

The bulk of the sulfur dioxide in the atmosphere arises from a small number of

fixed sources unlike the oxides of nitrogen which arise from a large number of widely

distributed sources. Consequently, sulfur dioxide measured at a particular location

will vary according to source strength and wind direction. Because of this, it is

difficult to relate the concentration observed by the District of Columbia to measurements made at the National Archives.

Sulfur dioxide was detected in the incoming air at all of the sample sites at

the National Archives. The hourly average concentrations are shown in Table 6. The

hourly average concentrations measured at 24th and L Streets, N.W. are shown in Table

7. The reason for the wide variation in concentrations at different locations and at

different times in the Archives is not known at the present time and, as yet, no attempt has been made to correlate results at a particular location to wind direction,

ambient temperature, or other meteorological parameters.

The significance of the sulfur dioxide measurements at the National Archives

became obvious when compared to the results obtained at the Madison Building and the

East Wing of the National Gallery. The sulfur dioxide concentration at these latter

two sites did not exceed the lower detectable limit. At the time of the analyses,

this limit was 0.0005 ppm at the Madison Building and 0.001 ppm at the East Wing of

the National Gallery. (It should be noted that during a period of about one hour on February 8, 1983 the instrument noise level was such that a detectable limit of

0.005 ppm was observed at the East Wing.) During the sampling periods at the Madison

Building and the National Gallery, the concentrations measured by the District

Government were consistently above the lower detectable limits (Table 7).

The concentrations measured in the Archives are consistently larger than those

measured at 24th and L Streets, N.W. If the averages of the two sets of measurements

are compared, it is found that the ratio of the average of the Archives measurements

to the average of the 24th and L Streets measurements is always less than 1.0.

5
However, the value ranges from 0.86 down to 0.16 with no obvious relationship between

location of intake and the ratio.

Results — Ozone

No significant concentration of ozone was found at any of the locations sampled

either in the National Archives, the Madison Building, or the East Wing of the

National Gallery. The data supplied by the District of Columbia (Table 8) indicated

a maximum of 21 ppb during any sampling period. Measurements made at the same time

at all locations were indistinguishable from zero. The explanation is that, given

a low ambient concentration to begin with and anticipating substantial losses in the

air handling system, it is reasonable to expect that little ozone will reach the

stack area. The situation may be quite different at times when the ambient ozone concentration is higher (such as during the summer or fall), but during the months of

December, January, and February, the absence of ozone inside the buildings is not

unexpected.

Other Measurements

The measurements at the National Archives summarized earlier in this report were

all made with the sample probes positioned directly in the air stream issuing from an inlet vent. This was done in order to assess the quality of the incoming air without

allowing the possibility of alteration of the composition by local materials or conditions. At several sample sites, the probes were removed from the inlet duct and were

placed in the stack area in a position out of direct line with the inlet vent. While

no change in the concentration of the oxides of nitrogen was observed, in several cases a reduction of up to 50 percent of the sulfur dioxide was seen. More often,

the reduction was less, but it occurred often enough to be of some potential interest.

Table 3 contains a qualitative summary of the effect observed at the various sites at

the National Archives.

Table 3. Difference of Sulfur Dioxide in the Stack Areas Compared to Incoming Air.

Location Observation

3E3 15% Reduction

1 E2A No difference

9E1 25% Reduction

7E4 Inconclusive

10E2 50% Reduction

9W4 Not measured in stack area

9W3 20% Reduction

9W2 50% Reduction

1 9W2 25% Reduction

17W1A 25% Reduction

3W2B Not measured in stack area

Caution should be exercised in drawing conclusions from these results without

further observations.

6
A series of ozone measurements were made in areas of the Archives at and near

several high-use copying machines to determine whether ozone was being generated by

the machines, and if so, whether it was being carried into document storage areas.

No significant difference was observed between the instrument readings in the immediate vicinity of the copying machines (area 7E1), the stack area directly over the

duplicating area (8E1), and measurements made at other locations throughout the

Archives. The measurements indicate that the copying machines are not contributing

a measurable amount of ozone to the atmosphere inside the National Archives.

Conclusions

The ventilating systems of the National Archives, the Madison Building of the

Library of Congress and the East Wing of the National Gallery of Art do not appreciably reduce the concentration of nitrogen oxides in the air which passes through

them. However, the ambient concentration of the oxides of nitrogen may decrease with

increasing altitude, and a system drawing air from rooftop level may exhibit a lower

concentration than a system with an inlet at ground level.

The measurements indicate that all sulfur dioxide is removed from the air

entering the systems at the Madison Building and the East Wing, while the concentration entering the system at the National Archives appears to pass through the system

with little or no change.

The effect of ventilating systems on the concentration of ozone could not be

determined primarily because of the relative absence of ozone in the atmosphere.

Acknowledgment

This work was sponsored by the National Archive and Record Service and by the

Public Building Service of the General Services Administration. We wish to thank

Mr. Amantha Padmanabha and the staff of the Air Monitoring Division of the Department

of Environmental Services of the District of Columbia for their advice and data.

7
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11

Concentrations

in

parts

per

billion

by

mole

(ppb).
Table 6. Hourly Average Concentrations 3 of Sulfur Dioxide Measured at the National

Archives

Sampling Location and Starting Date

3E3 1 E2A 9E1 7E4 1 0E2 9W4 9W3 9W2 1 9W2 17W1A 3W2B

Time 12/2/82 12/6 12/8 12/9 12/15 12/29 1/4/83 1/5 1/12 1/13 1/26

10 1 5 5 D 11 2 8 11 3 6 9 20

12 8 3 9 -- 4 5 9 9 16

A 13 12 2 9 2 — 2 5 9 9 16

14 9 8 4 6 2 5 6 8 9 18

Y 15 28 9 8 — 2 5 7 8 9 20

16 24 9 9 — 2 5 6 9 10 22

17 19 9 10 6 2 4 6 9 12 25

1 18 18 9 9 6 2 6 6 9 12 28

19 20 9 7 5 2 5 6 9 11 23

20 26 8 7 4 3 4 6 10 12 32

21 - - 8 7 4 5 4 6 10 12 34

22 — 9 6 3 7 4 6 10 16 30

23 8 6 2 6 4 6 9 17 30

24 -- 8 5 2 4 4 6 10 15 33

1 9 5 3 4 5 7 10 16 32

D 2 — 12 5 4 4 2 7 8 14 29

3 — 12 4 4 4 3 7 7 13 26

A 4 — 12 4 4 4 4 8 7 11 25

5 12 4 4 3 5 7 6 10 25

Y 6 -- 13 3 4 3 6 8 6 11 25

7 16 3 4 4 5 8 8 10 25

8 — 17 • 2 4 6 4 9 10 9 28

2 9 - - 10 2 3 3 4 12 5 8 21

10 12 11 1 2 3 2 9

11 11 5 1 13

12 12 5 11 13 5 9

14 5 8

15 5 8

16 5 9

17 4 10

18 5 8

19 5 8

20 5 8

21 5 10

22 7 11 23 8 10

24 7 7

1 D 2

3 A 4

5

Y 6

78

3 9

10

1112

Average 18 2

5

54

4

34

4

4

4

3

2

2 10 5 4 4

76

4

6

6

8

54

3

4 7 8 11 25

Concentrations in parts per billion by mole (ppb).

12
Table 7. Hourly Average Concentrations 3 of Sulfur Dioxide Measured by D.C. Government

at 24th and L Streets, N.W.

Starting Date

Time 12/2/82 12/6 12/8 12/9 12/15 12/29 1/4/83 1/5 1/12 1/13 1/26

10 14 24 26

D 11 4 18 28 10 24 27 29

12 30 4 16 - - 13 21 13 28 26

A 13 41 7 15 - - — 11 15 16 11 25 32

14 56 14 10 — 15 15 10 10 23 28

Y 15 99 17 8 - - 14 21 11 10 28 27

16 36 23 11 — 8 20 9 18 36 24

17 49 22 10 47 13 19 10 20 32 26

1 18 15 42 9 61 16 23 12 21 33 26

19 16 73 12 38 18 23 8 22 35 30

20 37 35 21 38 28 18 9 20 34 34

21 34 12 27 33 37 21 8 19 33 34

22 23 10 22 36 37 20 6 17 32 36

23 16 10 14 39 26 19 4 17 36 28

24 17 10 13 36 20 27 4 19 36 28

1 29 15 20 36 19 24 3 20 40 23

D 2 27 20 27 59 18 25 4 22 42 30

3 9 16 29 41 19 24 7 22 40 28

A 4 5 16 25 38 22 19 11 23 46 25

5 5 14 17 40 33 32 12 19 45 23

Y 6 10 16 25 24 28 34 15 20 35 26

7 26 24 29 10 30 36 23 27 33 29

8 34 27 47 15 30 25 50 28 32 46

2 9 33 13 48 25 26 24 25 25 32 40

10 27 7 20 20 30 18 25

11 17 29 13 15 25

12 28 18 14 34

13 13 25

14 14 27

15 13 29

16 13 35

17 15 38

18 16 44

19 15 43

20 16 37

21 29 35

22 25 43

23 20 41

24 16 26

1 17 21 D 2 12 22

3 7 27

A 4 7 14

5 8 18

Y 6 10 17

7 14 20

8 19 21

3 9 19 18

10 14

11 11 12 17

Average 29 7 20 21 23 22 23 21 19 34 29

Concentrations in parts per billion by mole (ppb)
Table 8. Ozone Measured at 24th and L Streets, N.W. by the District of Columbia.

Date

Concentration 3

Mean

of Ozone

Maximum

12/6/82 10 18

12/7/82 10 21

12/8/82 3 11 12/9/82 6 16

12/10/82 4 11

12/15/82 3 5

12/16/82 5 12

12/17/82 8 15

12/28/82 3 10

12/29/82 5 20

12/30/82 2 8

1/3/83 5 12

1/4/83 5 11 1/5/83 1 1 1/6/83 2 8

1/7/83 4 11 1/12/83 10 17

1/13/83 8 14

1/14/83 5 13

1/15/83 9 14

a -9

Concentrations in parts per billion by mole (1/10 ).

14
Table 9. Summary of Temperature and Relative Humidity Measurements.

Location

Temperature

Average Range

Relative

Average

Humidi ty

Range

3E3 21.1 20.5-21.4 57 55-58

1 E2A • 22.0 21.5-22.3 54 49-56

9E1 22.6 21.4-23.5 36 54-57

7E4 21.3 20.4-22.6 48 48-48

10E2 22.7 22.1-22.5 49 45-53

9W4 22.7 20.7-23.5 55 50-60

9W3 22.0 21.2-23.2 52 48-57

9W2 21.3 21.0-22.0 43 36-47

19W2 24.1 22.4-25.2 41 39-42

17W1A 22.2 21.6-22.8 50 49-52

3W2B 22,9 22.4-23.7 35 31-42

Madison Building 21.4 20.8-23.0 55 51-58

East Wing 21.8 21.3-22.2 54 52-56

Figures 1 - 5

A plot of the concentration of oxides of nitrogen measured at the indicated

location compared to a plot of the data of the District of Columbia measurements

made at 24th and L Streets, N.W., Washington, D.C.

15
OXIDES

OF

NITROGENPPM

OXIDES

OF

NITROGEN

-

PPM

16
TIME IN HOURS

17
Attachment: Report of the 1977 study at the National Archives building.

form NM-343

(U-W)

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D.C. 20234

REPORT OF ANALYSIS

of

The Atmosphere at Several Locations

in the National Archives

Requested by General Services Administration

Act No. 10477380, Document No. B0000051

Project No. 3100645

Introduction

Air from the ventilating system was analyzed for ozone,

oxides of nitrogen, and sulfur dioxide. The analyses were

performed separately and at different times for each of the

substances. Samples were obtained both in the stack areas

and at the receiving room loading platform. The stacks are

supplied with air from the ventilating system, while the

receiving room loading platform receives air from both the

interior of the building and directly from the outside.

Ozone was measured with a Dasibi Model 1003 AH ultraviolet

adsorption instrument. Oxides of nitrogen were measured

with a Monitor Labs Model 8440 Nitrogen Oxide analyzer.

Sulfur dioxide was measured with a Monitor Labs Model 8450

Sulfur Monitor.

Ozone

Ozone was measured in the location identified as 18-E-3,

5-E-3, and 7-W-2, and at the receiving room loading platform

on September 1, 1977.

The air in the room and the air coming directly out of a register of the ventilating system were sampled in the three

stack areas. The ozone concentration in all three areas was

essentially the same as the air delivered to the area by the

ventilating system. In area 5-E-3 and 7-W-2, the concentration in the room air was the same as in the incoming air,

but in area 18-E-3 the ozone concentration in the room air

was somewhat higher than the ozone content of the incoming

air. No explanation for this anomaly has been found.

18
The concentration of ozone at the loading platform was considerably higher than that found in any of the stack area

inlet air ducts. The high concentration probably reflects

the mixing of a large amount of outside air with some inside

air. The value of the concentration of ozone at this point

is similar to the ozone concentration measured by the District

of Columbia Air Monitoring Station at 427 New Jersey Avenue.

The results of the ozone measurements are summarized below:

Concentration Range in

Area Source Parts per Million by Volume

5-E-3 Incoming Air 0.005 - 0.012

5-E-3 Room Air 0.009 - 0.013

7-W-2 Incoming Air 0.000 - 0.006

7-W-2 Room Air 0.000 - 0.004

18-E-3 Incoming Air 0.009 - 0.020

18-E-3 Room Air 0.031 - 0.042

Rec Rm. Loading Platform 0.070 - 0.110

Outside Air 0.097*

*Value obtained from D.C. Government for period corresponding to sampling at Rec. Rm. Loading Platform.

Oxides of Nitrogen

Oxides of nitrogen were measured in area 5-E-3 and at the

loading platform of the receiving room on September 14 and

15, 1977. The value measured in the duct of 5-E-3 remained

at a concentration between 0.020 and .030 ppm between 3:00

p.m. on September 14, and 7:00 a.m. on September 15. The

concentration in the outside air measured by the D.C. Government ranged between 0.016 and 0.070 ppm during this period.

The average value was 0.041 ppm. The values measured in

area 5-E-3 did not reflect changes in the concentration of

the oxide of nitrogen in the outside air. At 7:00 a.m. on

September 14, the value of the concentration in area 5-E-3

began to rise, and reached a maximum of 0.060 ppm at 9:30

a.m. This rise was matched by a similar rise in the concentration in the outside air which began at 4:00 a.m. and

which reached a value of 0.080 ppm at 8:30. The measurements

by the D.C. Government were interrupted at this time, but

the trend in the concentration at the time was definitely

rising

.

f 19
The values of the oxides of nitrogen measured in the receiving room loading dock area ranged from a low of 0.055 ppm

to a high of 0.13 ppm during a one-hour sampling period

starting at 11:30 a.m. on September 14. The average value

for the same period measured by the D.C. Government was

about 0.06 ppm. The reason for the higher values inside the

building is no doubt due to auto exhaust gases generated by

vehicles moving in and out of the receiving room area.

Sulfur Dioxide

Sulfur dioxide was measured in area 5-E-3 and in the loading

dock area of the receiving room on November 29 and 30, 1977.

The concentration in the air entering the 5-E-3 area through

the ventilating system and the room air itself never exceeded

a concentration of 0.003 ppm sulfur dioxide.

Measurements made in the receiving room loading dock area

varied from a low value of 0.009 ppm to a high of 0.044 ppm.

The concentration measured in the area appeared to follow

the concentration of sulfur dioxide in the outside air as

measured by the D.C. Government. The concentration in the

outside air during the period of time when measurements were

being made in area 5-E-3 were between 0.032 and 0.040 parts

per million.

Conclusion

The maximum concentration of sulfur dioxide in the stack

areas does not exceed 0.003 ppm, although the outside air

contains more than ten times this concentration. The ozone

concentration in the stack area does not exceed 0.042 ppm

when the outside air contains as much as 0.097 ppm. It

appears, therefore, that substantial amounts of sulfur

dioxide and ozone are removed by passage of outside air

through the ventilating system.

Nitrogen dioxide concentration in the building appears to

respond to changes in the concentration of nitrogen dioxide

in the outside air and are probably not removed in substantial quantities by passage through the ventilating system.

Ernest E. Hughes, Res. Chemist

John K. Taylor, Chief

Air and Water Pollution Analysis Section

Robert W. Burke

Service Analysis Coordinator

Analytical Chemistry Division

January 30, 1978

20


APPENDIX C

NBSIR 83-2770

Air Exchange Rate Measurements

in the National Archives Building

August 1 983

Prepared for and sponsored by:

Public Buildings Service

General Services Administration

7th and D Streets, SW

Washington, DC 20407

and

National Archives and Records Service

National Archives Building

Washington, DC 20408

C-1

NBSIR 83-2770

AIR EXCHANGE RATE MEASUREMENTS

IN THE NATIONAL ARCHIVES BUILDING

Samuel Silberstein

Richard A. Grot

Douglas O. Pruitt Philip Engers

Patrick J. Lane

Steven E Schweinfurth

August 1 983

Prepared for and sponsored by:

Public Buildings Service

General Services Administration

7th and D Streets, SW

Washington, DC 20407

and

National Archives and Records Service

National Archives Building

Washington, DC 20408

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

Abstract

Air exchange measurements were carried out at the National

Archives Building under various combinations of temperature and

wind speed. The average air exchange rate under normal operation

of the heating, ventilating, and air-conditioning system (HVAC)

was 0.9 h~1 for an average temperature difference of 11.3°C and

an average wind speed of 2.7 m/s. This rate is approximately

twice those for n ew General Services Administration (GSA) office

buildings. No clear dependence of air exchange rate on

temperature differences up to 17°C or wind speeds up to 5 m/s was

found

.

With outdoor air dampers closed and fans operating, the

average air exchange rate was 1.2 h"^ for an average temperature

difference of 8.2°C and an average wind speed of 1.7 m/s.

A test of interzone air movement showed that air migrates

rapidly from non-stack to stack areas with fans operating

normally

.

The building could not be pressurized beyond an indooroutdoor pressure difference of 14 Pa. At this pressure

difference, the air exchange rate was 1.5 h-1. As in the case of

normal operation of the HVAC system, this rate is also

approximately twice those for new GSA office buildings.
J

. . 1

! .

' .

,

! • ; o.j
AIR EXCHANGE RATE MEASUREMENTS IN THE NATIONAL ARCHIVES BUILDING

INTRODUCTION

The National Bureau of Standards (NBS) was asked by the

General Services Administration (GSA) and the National Archives

and Records Service (NARS) to measure air exchange rates of the

National Archives Building under various conditions, including

pressurization. This was done to aid in evaluating whether use

of the current heating, ventilating, and ai r-conditionining

(KVAC) system is consistent with preservation of archival

records. The tests performed by NBS are as follows: 1) The air

exchange rate of the building was measured under normal operation

of the HVAC system. 2) The air exchange rate was measured with

outdoor air dampers closed in order to determine how much air

leakage was through dampers. 3) The air exchange rate was

measured with dampers closed and fans off in order to determine

how much the HVAC system contributes to air leakage. 4) Air

lea k age from the office and public areas to the stack areas was

measured. 5) Fan pressurization measurements were performed in

order to measure the intrinsic weather-independent envelope

tightness of the building.

METHODS

The National Archives Building

The National Archives Building, located between Pennsylvania

and Constitution Avenues, and between 7th and 9th Streets, in

downtown Washington, is pictured in Fig. 1. Its volume is

306,253.5 m3, according to GSA. A schematic diagram of the

building is shown in Fig. 2. The northern side of the building,

bordering on Pennsylvania Avenue, is composed of ten stories of

offices. Each of these stories is subdivided in the center of

the building into from one to three floors of stacks, where

records are stored. In addition, there are offices located on

several of the stack floors. Nine air handling systems serve the

building (other than the garage). Each system except for systems

2 ana 4 is composed of two supply fans and a return fan; systems

2 and 4 are composed of one supply and return fan each. All fans

in each system operate simultaneously. Fig. 2 shows the areas

served by each system.

Installation of automated tracer gas equipment

One set of tubes and wires was connected from each airhandling system to a computer and electron-capture gas

chromatography detector located in the basement. Each set of

tubes and wires consists of 1/16-inch inner diameter (id) plastic

tubing for injecting tracer gas into the supply fans, 1/4-inch id

plastic tubing for sampling return air, wiring connected to a thermistor to measure return air temperature, and wiring

connected to relays to determine whether fans were operating. In

aadition, a thermistor was placed outside the air intake of fan 1

1
to measure outdoor temperature, and a weather station was

installed on the roof to measure wind speed and direction. All

temperature and wind measurements were taken once a minute and

the results averaged each hour. In all tests other than those

for which fans were manually shut off, all fans operated

continuously. Outdoor air dampers were automatically modulated

by the building HVAC system and no record was kept of their

status

Automated tracer gas equipment used for all tests

The automated tracer gas system developed at NBS and

described elsewhere [1] was used to measure sulfur hexafluoride

concentration and calculate hourly air exchange rates for each of

the nine zones. The instrument was calibrated against samples

containing known concentrations of sulfur hexafluoride. At 50

minutes past the hour, the system injected sulfur hexafluoride

tracer gas for up to ten minutes. The maximal flow rate per zone

was 80 L/s. Concentrations at each location were measured by a gas chromatograph, electron capture detector at 10-minute

intervals thereafter and the results recorded on a floppy disk.

The last four concentrations were fit by regression analysis to

an equation of the form:

C = c 0 e-I' t (1)

where

I = air exchange rate, h“1

t = time after injection, h

C = concentration, ppb

C 0= initial concentration, ppb

A weighted average of the nine air exchange rates was

calculted and called the air exchange rate of the building. The

weighting factors were closely related to the flow rates of the

air handling systems. It would have been preferable to weight

air exchange rates by relative zone volumes but these data were

unavailable. Table 1 shows these flow rates and the weighting

factors. Average indoor temperature was calculated from the nine

return air temperatures. Because these temperatures were always

very close to each other, they were not weighted. Regression

analysis of air exchange rate vs. indoor-outdoor temperature

difference (always positive in these tests) was done essentially

as described elsewhere [2], Standard errors were also calculated

as described in reference 2.

In the earlier tests conducted from March 24, 1983 through

April 2, tracer gas was injected into each of the nine zones each

hour and its concentration permitted to decay. It was found that

gas was not always completely mixed within the first half hour.

It was also found that tracer gas often migrated into zones 1-5.

Therefore, for the later tests conducted from April 14 through

21, the system was programmed to inject gas once every three

hours for the full 10-minute injection period into zones 6-9

2
only. During the later tests, the tendency for gas to accumulate

in zones 1-5 was no longer noted. Tracer gas was permitted to

thoroughly mix during the first hour. During the third hour,

concentrations were low. Consequently only data collected during

the second hour were used. Fig. 3 shows that there is little

difference between earlier and later data.

Test 1. Normal operation of the HVAC system

No modifications of the HVAC system were required for tests

conducted under normal HVAC operation.

Test 2. Outdoor air dampers closed

To determine how much air leakage was through dampers, air

exchange rates were measured between March 25 and 28 after the

Archives maintenance staff shut all outdoor air dampers.

Test 3. Dampers closed and fans off

To determine how much the HVAC system contributes to air

leakage, air exchange rates were measured during the evening of

April 18 after the maintenance staff shut off the fans. Shutting

off the fans automatically closed the outdoor-air dampers.

Test 4. Air leakage from the office and public areas to the

stack areas

To determine whether air leaks into areas where archives are

stored (stacks) from other areas (non- stack areas), gas -was injected only into zones 1-5. Unlike during the earlier tests,

it mixed evenly throughout the building. (These data were also

used as normal fan-operation data.)

Test 5. Fan pressurization measurements

To measure the intrinsic weather-independent envelope

tightness of the building, a fan pressurization test was

conducted the evening of April 22. Sampling tubes leading from

systems 8 and 9 were rerouted to sample air in stack areas 7W-1

and 14W-1, both served by air-handling system 6, as seen in Fig.

1. Just prior to pressurizing the building, it was determined

that tracer-gas concentrations in these two stack areas were

nearly equal to that in return fan 6, suggesting that tracer gas

was uniformly distributed in that zone.

The maintenance staff shut off all the return air fans,

closed the exhaust air dampers, and fully opened the supply air

dampers (including dampers and fans serving the garage) prior to

tracer gas injection. Tracer gas was manually injected for 30

minutes at a flow rate of 0.25 L/s in order to maintain a high

enough concentration for the high air exchange rates anticipated

during the test. Differential pressure gauges were installed

across the entrance doorways on Pennsylvania and Constitution

Avenues. Since the concentrations in the two stack areas (and in

fact in the remaining 7 air-handling systems) were all nearly

3
constant during tracer gas injection at about 200 ppb, the air

exchange rate was calculated by the equation:

I = F/C-V (2)

where

F = tracer gas flow rate, m3/h

V = bu il di n g v ol um e , m-*

Pressurization was maintained for three hours after

injection was terminated. After injection was terminated, the

air exchange rate was also calculated by the computer in the

usual manner.

RESULTS

Test 1. Normal operation of the HVAC system

The results of air exchange rate measurements under normal

HVAC-system operation are shown in Table 2. Fig. 3 shows air

exchange rate measurements plotted against temperature difference

with wind speeds indicated next to the points. Curves

representing one standard error unit about the line are also

shown. The average air exchange rate v/as 0.9*0. 3 h"^,

corresponding to an average temperature difference (AT) of 11.3°C

and an average wind speed of 2.7 m/s. During normal operation of

the HVAC system, the average indoor temperature of the Archives

Building remained nearly constant at 22.8 ± 0.5°C (standard

deviation or sd). The best-fit regression line is given by the

eq uation

The correlation coefficient, R2, is 0.23, reflecting the large

amount of data scatter. The uncertainty of the first

coefficient, as measured by the standard error, is 972; the

uncertainty of the second coefficient is 212. It can be seen in

Fig. 3 that a linear relationship between I and AT going through

the origin cannot be excluded. Neither can the possibility that

I is independent of AT for AT below 17°C be excluded.

At constant at (this can be visualized, for example, by

going up any corridor 1°C wide in Fig. 3), air exchange rate does

not incrase with increasing wind speed; if anything, it

decreases. In fact, there is no apparent relationship between

air exchange rate and wind speeds of 0.6-5 m/s encountered during

the study.

I = 0.5 + 0.4 (AT) (3)

where

^out = outdoor temperature, °C

in A OUt» . 0

average indoor temperature,

4
Test 2. Outdoor air dampers closed

In order to determine how much air leakage was through

outdoor air dampers, a tracer-gas study was performed

with outdoor dampers closed. The results of air exchange rate

measurements with dampers closed are shown in Table 3. rig, 3

shows the results of this experiment compared with the results of

the previous study. The average air exchange rate was 1.2 h-1 at

an average temperature difference of 8.2°C and an average wind

speed of 1.7 m/s. Two distinct temperature difference regimes

make up this study: 1) small AT (4 data points below 2°C), and 2)

large AT (6 data points between 11 and 17°C). There are no data

directly comparable to the first regime in the study under normal

fan operation, but there are 20 points in the large AT region.

The two large at results are nearly identical: an air exchange

rate of 1.1*0. 2 h“1 at a temperature difference of 13.4°c and

wind speed of 1.6 m/ s with dampers closed, compared with an air

exchange rate of 1.0*0. 3 h”^ at a temperature difference of

13.5°C and wind speed of 2.8 m/s.

As in the case of normal HVAC-system operation, the large

data scatter make it difficult to assign a definite relationship

between AT and I. In the present instance, neither a direct nor

inverse dependence, nor independence of AT and I can be excluded.

The standard error bands are not drawn, but are so wide that they

encompass the origin and most of the normal HVAC-system operation

data. The combined normal HVAC-system operation and damperclosed data are about as well fit by I = 1 h“1 as by any other

rel ationship.

Test 3. Fans off and dampers closed

In order to determine how much the HVAC system contributes

to air leakage, a tracer-gas test was done in which fans were

turned on only at the beginning and end in order to mix the air,

but left off in the middle of the test for about two hours.

During this time, outdoor air dampers were also closed. An air

exchange rate could not be calculated from the data obtained by

this test because nearly all the gas ended up in zone 8

immediately after injection.

Test 4. Air leakage from the office and public areas to the

stack areas

It was determined from information supplied by GSA that airhandling systems 6-9 serve mainly the stacks, while systems 1-5

serve mainly the remainder of the building (Fig. 2). Therefore,

tracer gas was injected only into zones 1 to 5 in order to test

whether there was significant air leakage into the stack areas

from the rest of the building. It was found that there was

immediate, thorough mixing between the stack and non-stack areas.

The tracer gas concentrations in the nine zones were so uniform

during the test, in fact, that it was possible to calculate an

air exchange rate for the building (see Fig. 3 and Table 2,

5
4/19/83, hour 13).

Test 5. Fan pressuriz ation measurements

Fan pressurization measurements were performed in order to

measure the intrinsic weather-independent envelope tightness of

the building. The building was pressurized by closing off all

exhaust air dampers and return fans, including those serving the

garage, and opening all supply air dampers and fans.

Concentration measurements were made in two stack areas on the

7th and 14th stack floors. (There are 21 stack floors.) The

building could be pressurized to maximum pressure differences of

only 14 Pa, measured at the Constitution Avenue entrance on the

ground floor (corresponding to the fifth stack floor) and 10 Pa

at the Pennsylvania Avenue entrance on the main floor

(corresponding to the third stack floor). It was noticed during

the test that there were strong drafts from the garage through

two doorways into the main body of the building. The average

temperature difference during the test was 5.9°C and the average

wind speed was 1.5 m/s.

The air exchange rate calculated by the constant

concentration method (equation 2) was 1.5 h-1. Air exchange

rates were also calculated by the concentration-decay method

(equation 1) for two hours. As shown in Table 4, these air

exchange rates were 0.0 h"1 for the 14th floor for both hours and

0.1 and 0.4 h“1 for the 7th floor. The rates calculated by the

concentration decay method may even be lower than expected in the

absence of pressurization (Fig. 3).

CONCLUSIONS AND RECOMMENDATIONS

Air exchange measurements were taken under various

combinations of temperature and wind speed. The average air

exchange rate was 0.9 h"1 for an average temperature difference

of 11.3°C and an average wind speed of 2.7 m/s. The indoor

temperature was very nearly constant at around 23°C and the

outdoor temperature was always lower than the indoor temperature.

No clear dependence of air exchange rate on temperature

differences up to 17°C or wind speeds up to 5 m/s was found. If a more complete assessment of the National Archives Building is

desired, then further air exchange rate measurements would need to

be taken at different times of the year, and at higher wind

speeds than those encountered during the tests.

The test done with air dampers closed and fans operating

showed that at a temperature difference between 11 and 17°C, the

air exchange rate was the same as that when dampers were

operating automatically. This may be because under normal

operation of the HVAC system, dampers would be closed at these

outdoor temperatures. It would be useful to conduct this type of

test under different weather conditions and record damper opening

and closing.

The test with dampers closed and fans off resulted in tracer

gas ending up in one zone (8), so no useful results could be

obtained.

6
A test of interzone air movement showed that air migrates

rapidly from non-stack to stack areas with fans operating

normally

.

The building could not be pressurized beyond an indooroutdoor pressure difference of 14 Pa. There was some doubt about

the resulting air exchange rate obtained at this pressure

difference since a rate of 1.5 h-1 was obtained by the constant

concentration method and rates under 0.5 h-1 were obtained by the

tracer-gas decay method. The first air exchange rate seems more

likely because it is at least higher than air exchange rates in

the absence of pressurization.

There are uncertainties as to the exact areas served by the

various air-handling systems (Fig. 2) and this tubing and wiring

could prove invaluable in accurately charting the building. For

this reason, and to conduct further tests described below, it is

recommended that the tubing and wiring be left in place.

A similar study of eight new GSA buildings in various parts

of the United States (unpublished data) shows that the Archives

Building is about twice as leaky as new office buildings, both

under normal operation of the HVAC system and under

pressurization. Their air exchange rates under normal operation

of the HVAC systems vary from 0.2 to 0.6 h“1 for outdoor

temperatures of 4-10°C and wind speeds under 1.3 m/s. Their air

exchange rates at a pressure difference of 14 Pa were 0.5 to 0.9

h-1

.

ACKNOWLEDGMENT

We wish to thank Ron Diggs, Lewis Johnson, Louis Olsen, Dan

Poyner, and Joe Schaefer of GSA for their invaluable assistance

in carrying out the tests.

REFERENCES

1. R. A. Grot, C. M. Hunt and D. Harrje, "Tracer gas automated

equipment for complex building studies," pp. 103-128 in "First

Air Infiltration Center (AIC) Conference: Air infiltration and

measuring techniques, Proceedings," AIC, Bracknell, UK, 1980.

2. S. Silberstein, "Air leakage measurements of an unpartitioned

mobile home," National Bureau of Standards Interagency Report 80-

2105, Washington, 1980.

7
VO

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TABLE 1. Air Handling System Flow Rates and Air Exchange Rate

Weighting Factors.

Sy stem

1

Flow rate

1 0 3 cfm, m3/s

Air exchange rate

weighting factor

69 33 1 5.9 2 . 8 0.09

62 29 1 5.9 2.8 0.09

40 19 0.6

70 33 1 65 31 1 66 31 1 66 31 1

8
TABLE 2. Air Exchange Rates under Normal HVAC-System Operation

LEGEND

W SPEED = wind speed, m/s

W DIR = wind direction, degrees clockwise from north

T-OUT = outdoor temperature, °C

T-IN = average indoor temperature, °C

T-DIFF = T-IN - T-OUT, oC

AER = average air exchange rate, h“1

(weighting factors in Table 1)

RET = return air fan

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF AER

3/24/83 18 2.2 45.0 7.7 22.4 14.7 1.23

RET 1 = 1.44

RET 2 Z 1.14

RET 3 Z 1.63

RET 4 z 1.52

RET 5 z .83

RET 6 z .88

RET 7 z 1.20

RET 8 z 1.20

RET 9 = 1.22

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF AER

3/24/83 22 2.2 45.0 7.3 22.3 15.0 .94

RET 1 = 1.04

RET 2 z 1.39

RET 3 z 1.36

RET 4 z 1.36

RET 5 z .91

RET 6 z .60

RET 7 z .66

RET 8 z .58

RET 9 = 1.37

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF AER

3/24/83 23 2.6 45.0 7.2 22.2 15.0 .87

RET 1 - 1.41

RET 2 z 1.40

RET 3 z 1.33

RET 4 z 1.15

RET 5 z .77

RET 6 z .70

RET 7 z .51

RET 8 z .62

RET 9 z .66

9
TABLE 2 (continued)

DATE HOUR W SPEED W DIR T-OUT T- IN T-DIFF

3/25/83 1 3.0 45.0 6.9 22. 1 15.2

RET 1 = 1.34

RET 2 z 1.17

RET 3 z 1.64

RET 4 z 1.38

RET 5 z .77

RET 6 z 1.56

RET 7 z 2.13

RET 8 z 2.19

RET 9 = 1.90

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

3/25/83 8 2.7 67.5 5.1 21.9 16.8

RET 1 = 1.16

RET 2 z 1.05

RET 3 z 1.01

RET 4 z 1.03

RET 5 z .67

RET 6 z .59

RET 7 z .85

RET 8 z .81

RET 9 = .73

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

3/25/83 9 2.8 67.5 5.4 22.1 16.7

RET 1 = 1.48

RET 2 z 1.72

RET 3 z 1.75

RET 4 z 1.53

RET 5 z .74

RET 6 z 1.32

RET 7 z 1.64

RET 8 z 1.50

RET 9 = 1.24

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

3/25/83 14 2.7 112.5 8.4 22.4 14.0

RET 1 - 1.38

RET 2 z 1.26

RET 3 z 1.73

RET 4 z 1.49

RET 5 z .71

RET 6 z .90

RET 7 z 1.48

RET 8 z 1.58

RET 9 z 1.00

AER

1.69

AER

.85

AER

1.43

AER

1.29

10
TABLE 2 (continued)

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF

/ 25/ 83 15 2.9 90.0 8.9 22.4 13.5

RET 1 = 1.98

RET 2 z 1.54

RET 3 z 1.97

RET 4 z 1.45

RET 5 z .52

RET 6 z .97

RET 7 z 1.39

RET 8 z 1.48

RET 9 = .58

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

/ 1/83 18 1.5 1 80.0 14.8 23.4 8.6

RET 1 1.70

RET 2 z 1.92

RET 3 z 2.72

RET 4 z 1.33

RET 5 z .36

RET 6 z 0.00

RET 7 z .22

RET 8 z .44

RET 9 - 1.81

DATE HOUR VJ SPEED W DIR T-OUT T-IN T-DIFF

/ 2/83 2 .6 67.5 10.9 23.2 12.3

RET 1 = 1.36

RET 2 z 2.30

RET 3 z 1.30

RET 4 z .32

RET 5 z .39

RET 6 z .16

RET 7 z .60

RET 8 z .49

RET 9 = 1.13

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

714/83 13 2.6 157.5 18.5 23.0 4.5

RET 1 = .91

RET 2 z .43

RET 3 z 0.00

RET 4 z .26

RET 5 z 0.00

RET 6 z .66

RET 7 z .45

RET 8 z .61

RET 9 z .57

1

1

AER

1.32

AER

1.09

AER

.81

AER

.48
TABLE 2 (continued)

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF

/ 14/83 16 4.2 135.0 17.8 22.8 5.0

RET 1 = .73

RET 2 = .38

RET 3 :.78

RET 4 z .32

RET 5 z .63

RET 6 z .38

RET 7 z .43

RET 8 z .74

RET 9 = .26

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

/ 1 4/ 83 19 3.3 135.0 16.4 23.0 6.6

RET 1 = 1.98

RET 2 z .55

RET 3 z .80

RET 4 z .51

RET 5 z .54

RET 6 z .47

RET 7 z .58

RET 8 z 1.37

RET 9 = .70

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

714/83 22 2.1 135.0 16.1 23.0 6.9

RET 1 = 1.92

RET 2 z .49

RET 3 z .57

RET 4 z .70

RET 5 z .74

RET 6 z .60

RET 7 z .56

RET 8 z 1.58

RET 9 = .34

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

1/15/83 1 1.9 157.5 15.8 23.1 7.3

RET 1 = 2.20

RET 2 z .76

RET 3 z 1.18

RET 4 z .31

RET 5 z .30

RET 6 z .31

RET 7 z .76

RET 8 z .68

RET 9 z .82

AER

.55

AER

.93

AER

.89

AER

.92

12
TABLE 2 (continued)

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF

/I 5/ 83 4 1.9 157.5 16.6 23.1 6.5

RET 1 - 1.37

RET 2 z .32

RET 3 z 1 . 06

RET 4 z .49

RET 5 z .53

RET 6 z .89

RET 7 z .41

RET 8 z 1.20

RET 9 - .84

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

/I 5/ 83 7 2.6 157.5 17.7 23.2 5.5

RET 1 = 1.26

RET 2 z .70

RET 3 z .42

RET 4 z .63

RET 5 z .47

RET 6 z .46

RET 7 z .47

RET 8 z .29

RET 9 = .34

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

/I 5/ 83 10 2.3 180.0 18.6 23.7 5.1

RET 1 = 1.48

RET 2 z .71

RET 3 z .35

RET 4 z .48

RET 5 z .82

RET 6 z .65

RET 7 z .53

RET 8 z .58

RET 9 = .64

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

1/18/83 4 2.5 292.5 9.7 22.2 12.5

RET 1 = 1.48

RET 2 z 0.00

RET 3 z 1.70

RET 4 z .14

RET 5 z .93

RET 6 z .95

RET 7 z .88

RET 8 z .38

RET 9 z .98

AER

.91

AER

.54

AER

.71

AER

1.02

13
TABLE 2 (continued)

DATE HOUR W SPEED W DIR T-OUT T- IN T-DIFF

4/18/83 7 2.3 292.5 10.8 22.3 11.5

RET 1 = .71

RET 2 z .90

RET 3 z .91

RET 4 z 1.46

RET 5 z .71

RET 6 z .49

RET 7 z 1.44

RET 8 z 2.55

RET 9 = 1.69

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

4/18/83 10 2.0 270.0 10.0 22.8 12.8

RET 1 = .84

RET 2 z .71

RET 3 z 1.12

RET 4 z .35

RET 5 z .38

RET 6 z .79

RET 7 z . 80

RET 8 z .58

RET 9 = .53

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

4/18/83 13 1.8 270.0 11.9 23.0 11.1

RET 1 = 1.46

RET 2 z 1 .56

RET 3 z 1.00

RET 4 z .48

RET 5 z 0.00

RET 6 z .62

RET 7 z .31

RET 8 z 1.19

RET 9 = 1.10

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

4/18/83 22 2.1 67.5 11.1 22.9 11.8

RET 1 = .47

RET 2 z .32

RET 3 z 1.01

RET 4 z .74

RET 5 z .72

RET 6 z .13

RET 7 z .56

RET 8 z .56

RET 9 z .92

AER

1.24

AER

.74

AER

.86

AER

.62

14
TABLE 2 (continued)

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF

/ 19/83 1 2.6 112.5 10.3 22.8 12.5

RET 1 - 1.52

RET 2 z .15

RET 3 z .23

RET 4 z .68

RET 5 z .75

RET 6 z .62

RET 7 z .64

RET 8 z .53

RET 9 = 2.43

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

/I 9/ 83 7 3.6 225.0 10.2 22.7 12.5

RET 1 = .94

RET 2 z 0.00

RET 3 z 1.76

RET 4 z .55

RET 5 z .34

RET 6 z .62

RET 7 z .75

RET 8 z .57

RET 9 = 1.62

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

/I 9/ 83 13 4.5 270.0 10.9 23.7 12.8

RET 1 = 1.25

RET 2 z 1.41

RET 3 z 1.31

RET 4 z 1.02

RET 5 z .08

RET 6 z .77

RET 7 z .23

RET 8 z .61

RET 9 = .64

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

719/83 16 4.3 202.5 12.2 23.7 11.5

RET 1 = 1.29

RET 2 z .71

RET 3 z .57

RET 4 z .47

RET 5 z .41

RET 6 z .90

RET 7 z .23

RET 8 z .75

RET 9 z .29

AER

.96

AER

.96

AER

.75

AER

.65

15
TABLE 2 (continued)

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF AER

4/19/83 19 5.0 292.5 9.6 23.4 13.8 .68

RET 1 = 1 .10

RET 2 z .01

RET 3 z .49

RET 4 z .62

RET 5 z .33

RET 6 z .40

RET 7 z .48

RET 8 z .55

RET 9 z 1.35

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF AER

4/19/83 22 4.1 292.5 8.6 23.2 14.6 .59

RET 1 = 1.02

RET 2 z 1.13

RET 3 z .73

RET 4 z .73

RET 5 z .61

RET 6 z .75

RET 7 z .35

RET 8 z .59

RET 9 z .06

16
TABLE 3. Air Exchange Rates with Fans Off and Outdoor Dampers Closed

LEGEND

W SPEED = wind speed, m/s

W DIR = wind direction, degrees clockwise from north

T-OUT = outdoor temperature, °C

T-IN = average indoor temperature, °C

T-DIFF = T-IN - T-OUT, oc

AER = average air exchange rate, h

- "* (weighting factors in Table 1)

RET = return air fan

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF AER

3/25/83 18 2.1 45.0 9.6 22.5 12.9 .86

RET 1 - 2.01

RET 2 z 1.05

RET 3 z 1.13

RET 4

- .99

RET 5 z .46

RET 6

- .26

RET 7 z .81

RET 8 z .50

RET 9 = .64

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF AER

3/25/83 21 1.5 22.5 9.7 22.2 12.5 1.17

RET 1 = 1.97

RET 2 z 1.05

RET 3 z .97

RET 4 z 1.09

RET 5 z .76

RET 6 z .77

RET 7 z .68

RET 8 z 1.03

RET 9 = 1.86

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF AER

3/25/83 22 1.6 45.0 8.7 22.2 13.5 .83

RET 1 = 1.03

RET 2 z 1.48

RET 3 z 1.03

RET 4 z 1.29

RET 5 z .46

RET 6 z .46

RET 7 z .49

RET 8 z .62

RET 9 z 1.43

17
TABLE 3 (continued)

DATE HOUR VI SPEED W DIR T-OUT T-IN T-DIFF

3/25/83 23 1.6 45.0 8.5 22. 1 13.6

RET 1 = 1 . 80

RET 2 Z 1.43

RET 3 Z 1.31

RET 4 z 1.11

RET 5 z .84

RET 6 z .68

RET 7 z .87

RET 8 z .73

RET 9 = 1.64

DATE HOUR w SPEED VI DIR T-OUT T-IN T-DIFF

3/26/83 0 1.4 45.0 9.2 22.0 12.8

RET 1 = 2.50

RET 2 z 1.79

RET 3 z 1.26

RET 4 z 1.08

RET 5 z .90

RET 6 z .73

RET 7 z .93

RET 8 z 1.03

RET 9 = 2.24

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

3/26/83 2 1.1 90.0 6.4 21.4 15.0

RET 1 = 2.10

RET 2 z 2.16

RET 3 z .78

RET 4 z 1 . 10

RET 5 z .43

RET 6 z .49

RET 7 z .54

RET 8 z .98

RET 9 = 1.14

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

3/27/83 12 3.1 112.5 18.8 19.9 1.1

RET 1 = 1.79

RET 2 z 1.79

RET 3 z 2.07

RET 4 z 1.63

RET 5 z .46

RET 6 z .81

RET 7 z .54

RET 8 z 1.95

RET 9 z .92

AER

1.14

AER

1.40

AER

.97

AER

1.28

18
TABLE 3 (continued)

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF AER

3/27/83 18 1.1 270.0 19.6 19.9 .3 1.96

RET 1 = 1.67

RET 2 Z 2.19

RET 3 Z 3.24

RET 4 Z 1.82

RET 5 z 1.52

RET 6 z 1.24

RET 7 z 1.57

RET 8 z 1.75

RET 9 = 2.57

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF AER

3/27/ S3 22 2.0 270.0 19.8 19.9 .1 1.09

RET 1 = 1.91

RET 2 z 2.08

RET 3 z 2.16

RET 4 z .68

RET 5 z 0.00

RET 6 z .90

RET 7 r 0.00

RET 8 — .91

RET 9 - 1.25

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF AER

3/28/83 2 1.4 292.5 19.5 19.7 .2 1.55

RET 1 = 2.44

RET 2 z 2.24

RET 3 z 1.75

RET 4 z 2.04

RET 5 z .92

RET 6 z .69

RET 7 z .63

RET 8 z 1.03

RET 9 z 3.01

19
TABLE 4. Air Exchange Rates with Building Pressurized to 8-14 Pa

W SPEED = wind speed, m/s

W DIR = wind direction, degrees clockwise from north

T-OUT = outdoor temperature, °C

T-IN = average indoor temperature, °C

T-DIFF = T-IN - T-OUT, °C

RET = return air fan

7W-1 and 14W-1 = stack areas

DATE HOUR W SPEED W DIR T-OUT T-IN T-DIFF

i/21/83 19 1.4 292.5 17.9 23.8 5.9

RET 1 = .09

RET 2 Z .12

RET 3 z .39

RET 4 .01

RET 5 .18

RET 6 z .56

RET 7 z .26

1 4 W — 1 z .02

7W-1 - .14

DATE HOUR w SPEED W DIR T-OUT T-IN T-DIFF

1/21/83 20 .9 315.0 17.8 24.0 6.2

RET 1 = .39

RET 2 = .27

RET 3 z .20

RET 4 z .14

RET 5 z .15

RET 6 z .12

RET 7 z .14

14W-1 z 0.00

7W-1 z .43

20
Figure 1. The National Archives Building,

Pennsylvania and Constitution Avenues, and

Streets, in downtown Washington.

located between

between 7th and 9 th

21
•e * tr STACK X cc ff o (0 « o

H _I (A U.

2 1

19

18

17

16

15

14

13

12

1

10

9

8

7

6

5

4

3

2

1

u.O

u- _i Oil

$2 u <

U. CD Ui IL 3 H

O a. <

8 A, 9 A

3B

4

3

2

M

1A.3B

1 A,

3 A, SB

1 A,3 A,

3B.4.5B

1 A, 3 A

Figure 2. Schematic side view of National Archives Building,

showing areas served by air-handling systems, from information

supplied by GSA. Each of the nine air-handling systems of the

building except 2 and 4 has two supply air fans labelled "A" and

"B", and one return air fan; systems 2 and 4 have one supply and

return fan each. All fans in each system operate simultaneously.

The numbers in the figure above refer to supply fans.

22
2.0

A1.1

Figure 3. Relationship of air exchange rate to indoor-outdoor

temperature difference and wind speed under normal fan operation

and with outdoor air dampers closed. Wind speeds (m/s) are

shown to the right of data points. Solid line is best-fit

regression line for normal HVAC-system operation. Curves

represent 1 standard error unit on each side of regression line.

Dotted line is best fit regression line for outdoor air dampers

closed. O , normal operation, early tests (see Methods); ,

normal operation, late tests (see Methods); D , normal operation

(late test), test of air mixing between stack areas and other

areas; A, outdoor air dampers closed; • , normal operation

average; , outdoor air dampers closed average; + , overall

average.

23
WBI.II4A >««v. »«»oi U.». D(PT. OF COMM. BIBLIOGRAPHIC DATA

SHEET (See Instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 83-2795

2. Performing Organ, Report No,| t. Publication Date November 1983

4. TITLE AND SUBTITLE

Air Quality Criteria for Storage of Paper-Based Archival Records

5. author(S) Robert G. Mathey, Thomas K. Faison, Samuel Silberstein, James E. Woods,

ffaryeft B^Jghnson, William P. Lull, Charles A. Madson, Amos Turk, Karl L. Westlin,

6. PERFORMING ORGANIZATION (If joint or other than N BS, see instructions

)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

I. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State, ZIP)

National Capital Region National Archives and Records Service

Public Buildings Service Washington, D.C. 20408

General Services Administration

Washington, D.C. 20407

10. SUPPLEMENTARY NOTES

This report, NBSIR 83-2795, uses previously approved

MBS I R 83-2767 and NBSIR 83-2770 as appendices

Document describes a computer program; SF-185, FIPS Software Summary, Is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant Information. If document Includes a significant

bibliography or literature survey, mention It here) Criteria for temperature, relative humidity, and gaseous and particulate contaminant

concentrations are proposed for spaces used for storage and preservation of paperbased archival records. The criteria are based on available information from the

literature, and recommendations of the January 19-20, 1983, National Bureau of

Standards Workshop on Environmental Conditions for Archival Storage. Methods are discussed for meeting these criteria. Air quality criteria are proposed for different categories for archival storage. Factors to consider in the design of

archival storage facilities are addressed and recommendations made to aid in the

design of environmental conditioning systems for these facilities. A review of

literature describes the damage that may be caused by high temperature, high and low

relative humidity, and air pollutants to paper-based records.

Results of measurements of temperature, relative humidity, air exchange rate, and

gaseous contaminant concentrations (sulfur dioxide, nitrogen oxides, and ozone) in

the National Archives Building in Washington, D.C., are presented. These measurements are compared with those made in other buildings having controlled environments.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

air quality; archival storage; criteria; design parameters; environmental conditioning

systems; environmental conditions; environmental control; preservation .

13. AVAILABILITY

rXl Unl Imited Q] For Official Distribution. Do Not Release to NTIS

~] Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

[JC| Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

109

15. Price $13

USCOMM-DC 6O43-P80