ASTM D6245-98
(Guide)Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation
Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation
SCOPE
1.1 This guide describes how measured values of indoor carbon dioxide (CO2) concentrations can be used in evaluation of indoor air quality and building ventilation.
1.2 This guide describes the determination of CO2 generation rates from people as a function of body size and level of physical activity.
1.3 This guide describes the experimentally-determined relationship between CO2 concentrations and the acceptability of a space in terms of human body odor.
1.4 This guide describes the following uses of indoor CO2 concentrations to evaluate building ventilation-mass balance analysis to determine the percent outdoor air intake at an air handler, the tracer gas decay technique to estimate whole building air change rates, and the constant injection tracer gas technique at equilibrium to estimate whole building air change rates.
1.5 This guide discusses the use of continuous monitoring of indoor and outdoor CO2 concentrations as a means of evaluating building ventilation and indoor air quality.
1.6 This guide discusses some concentration measurement issues, but it does not include or recommend a method for measuring CO2 concentrations.
1.7 This guide does not address the use of indoor CO2 to control outdoor air intake rates.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: D 6245 – 98
Standard Guide for
Using Indoor Carbon Dioxide Concentrations to Evaluate
Indoor Air Quality and Ventilation
This standard is issued under the fixed designation D 6245; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope Zone by Means of Tracer Gas Dilution
2.2 Other Documents
1.1 This guide describes how measured values of indoor
ASHRAE Standard 62 Ventilation for Acceptable Indoor
carbon dioxide (CO ) concentrations can be used in evalua-
Air Quality
tions of indoor air quality and building ventilation.
1.2 This guide describes the determination of CO genera-
3. Terminology
tion rates from people as a function of body size and level of
3.1 Definitions—For definitions and terms used in this
physical activity.
guide, refer to Terminology D 1356.
1.3 This guide describes the experimentally-determined re-
3.2 Definitions of Terms Specific to This Standard:
lationship between CO concentrations and the acceptability of
3.2.1 air change rate, n—the total volume of air passing
a space in terms of human body odor.
through a zone to and from the outdoors per unit time, divided
1.4 This guide describes the following uses of indoor CO
–1 –1
by the volume of the zone (s ,h ).
concentrations to evaluate building ventilation–mass balance
3.2.2 bioeffluents, n—gases emitted by people as a product
analysis to determine the percent outdoor air intake at an air
of their metabolism that can result in unpleasant odors.
handler, the tracer gas decay technique to estimate whole
3.2.3 single-zone, n—an indoor space, or group of spaces,
building air change rates, and the constant injection tracer gas
wherein the CO concentration is uniform and that only
technique at equilibrium to estimate whole building air change
exchanges air with the outdoors.
rates.
1.5 This guide discusses the use of continuous monitoring
4. Summary of Guide
of indoor and outdoor CO concentrations as a means of
4.1 When investigating indoor air quality and building
evaluating building ventilation and indoor air quality.
ventilation, a number of tools are available to understand the
1.6 This guide discusses some concentration measurement
building being studied. One such tool is the measurement and
issues, but it does not include or recommend a method for
interpretation of indoor and outdoor CO concentrations. Using
measuring CO concentrations.
CO concentrations to evaluate building indoor air quality and
1.7 This guide does not address the use of indoor CO to
ventilation requires the proper use of the procedures involved,
control outdoor air intake rates.
as well as consideration of several factors related to building
1.8 This standard does not purport to address all of the
and ventilation system configuration, occupancy patterns, non-
safety concerns, if any, associated with its use. It is the
occupant CO sources, time and location of air sampling, and
responsibility of the user of this standard to establish appro-
instrumentation for concentration measurement. This guide
priate safety and health practices and determine the applica-
discusses ways in which CO concentrations can be used to
bility of regulatory limitations prior to use.
evaluate building indoor air quality and ventilation.
4.2 Section 6 discusses the rate at which people generate
2. Referenced Documents
CO and the factors that affect this rate.
2.1 ASTM Standards:
4.3 Section 7 discusses the use of indoor concentrations of
D 1356 Terminology Relating to Sampling and Analysis of
2 CO as an indicator of the acceptability of a space in terms of
Atmospheres
perceptions of human body odor.
D 3249 Practice for General Ambient Air Analyzer Proce-
2 4.4 Section 8 describes the use of mass balance analysis to
dures
determine the percent outdoor air intake at an air handler based
E 741 Test Method for Determining Air Change in a Single
1 3
This guide is under the jurisdiction of ASTM Committee D-22 on Sampling and Annual Book of ASTM Standards, Vol 04.11.
Analysis of Atmospheres and is the direct responsibility of Subcommittee D22.05on Available from American Society of Heating, Refrigerating, and Air-
Indoor Air. Conditioning Engineers, Inc., 1791 Tullie Circle, NE, Atlanta, GA 30329.
Current edition approved March 10, 1998. Published May 1998. A common way of expressing air change rate units is ach = air changes per
Annual Book of ASTM Standards, Vol 11.03. hour.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 6245
on the measured CO concentrations in the supply, return, and mass balance of CO in the building and is sometimes
2 2
outdoor air intake airstreams. presented with little or no discussion of its limitations and the
4.5 Section 9 describes the use of the tracer gas decay assumptions on which it is based. As a result, in some cases,
technique to determine building air change rates using the technique has been misused and indoor CO concentration
occupant-generated CO as a tracer gas. The tracer gas decay measurements have been misinterpreted.
technique is described in detail in Test Method E 741, and this 5.4 When the assumptions upon which equilibrium analysis
section discusses the application of this test method to the is based are valid, the technique can yield reliable measure-
special case of occupant-generated CO after the occupants ments of outdoor air ventilation rates. In addition, indoor CO
2 2
have left the building. concentrations can be used to determine other aspects of
4.6 Section 10 describes the use of the constant injection building ventilation when used properly. By applying a mass
tracer gas technique with occupant-generated CO to estimate balance at an air handler, the percent outdoor air intake in the
outdoor air ventilation rates. This technique is sometimes supply airstream can be determined based on the CO concen-
referred to as equilibrium analysis, and Section 10 discusses trations in the supply, return, and outdoor air. This percentage
the use of this technique and the assumptions upon which it is can be multiplied by the supply airflow rate of the air handler
based. to yield the outdoor air intake rate of the air handler. In
4.7 Section 11 discusses the use of continuous monitoring of addition, the decay of indoor CO concentrations can be
CO concentrations as a means of evaluating indoor air quality monitored in a building after the occupants have left to
and ventilation in buildings. In this discussion, continuous determine the outdoor air change rate of the building.
refers to real-time concentration measurement recorded with a 5.5 Continuous monitoring of indoor and outdoor CO
datalogging device over several days. concentrations can be used to study some aspects of ventilation
4.8 Section 12 discusses CO concentration measurement system performance, the quality of outdoor air, and building
issues, including measuring outdoor concentrations, sample occupancy patterns.
locations for indoor concentration measurements, establishing
6. CO Generation Rates
the uncertainty of measured concentrations, and calibration.
6.1 Human metabolism consumes oxygen and generates
5. Significance and Use
CO at rates that depend on the level of physical activity, body
5.1 Indoor CO concentrations have been described and size, and diet.
used by some people as an indicator of indoor air quality. These 6.2 The rate of oxygen consumption V in L/s of a person
O
uses have included both appropriate and inappropriate inter- is given by Eq 1:
pretations of indoor CO concentrations. Appropriate uses
0.00276 A M
D
V 5 (1)
include estimating expected levels of occupant comfort in O
~0.23 RQ 1 0.77!
terms of human body odor, studying occupancy patterns,
where:
investigating the levels of contaminants that are related to
A = DuBois surface area m ,
occupant activity, and screening for the sufficiency of ventila- D
M = metabolic rate per unit of surface area, met (1 met =
tion rates relative to occupancy. Inappropriate uses include the
58.2 W/m ), and
application of simple relationships to determine outdoor air
RQ = respiratory quotient.
ventilation rates per person from indoor CO concentrations
The DuBois surface area equals about 1.8 m for an
without verifying the assumptions upon which these relation-
average-sized adult and ranges from about 0.8 to 1.4 m for
ships are based, and the interpretation of indoor CO concen-
elementary school aged children. Additional information on
trations as a comprehensive indicator of indoor air quality.
body surface area is available in the EPA Exposure Factors
5.2 Outdoor air ventilation rates affect contaminant levels in
Handbook (2). The respiratory quotient, RQ, is the ratio of the
buildings and building occupants’ perception of the acceptabil-
volumetric rate at which CO is produced to the rate at which
ity of the indoor environment. Minimum rates of outdoor air
oxygen is consumed. Therefore, the CO generation rate of an
ventilation are specified in building codes and indoor air
individual is equal to V multiplied by RQ.
O
quality standards, for example, ASHRAE Standard 62. The
6.3 Chapter 8 of the ASHRAE Fundamentals Handbook,
compliance of outdoor air ventilation rates with relevant codes
Thermal Comfort (1), contains typical met levels for a variety
and standards are often assessed as part of indoor air quality
of activities. Some of these values are reproduced in Table 1.
investigations in buildings. The outdoor air ventilation rate of
6.4 The value of the respiratory quotient RQ depends on
a building depends on the size and distribution of air leakage
diet, the level of physical activity and the physical condition of
sites, pressure differences induced by wind and temperature,
the person. It is equal to 0.83 for an average adult engaged in
mechanical system operation, and occupant behavior. Given all
light or sedentary activities. RQ increases to a value of about 1
of this information, ventilation rates are predictable; however,
for heavy physical activity, about 5 met. Based on the expected
many of these parameters are difficult to determine in practice.
variation in RQ, it has only a secondary effect on CO
Therefore, measurement is required to determine outdoor air
generation rates.
change rates reliably.
6.5 Fig. 1 shows the dependence of oxygen consumption
5.3 The measurement of CO concentrations has been
promoted as a means of determining outdoor air ventilation
rates per person. This approach, referred to in this guide as 6 2
The body surface area A in m can be estimated from the formula A =
D D
0.725 0.425
equilibrium analysis, is based on a steady-state, single-zone 0.203H W where H is the body height in m and W is the body mass in kg (1).
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 6245
TABLE 1 Typical Met Levels for Various Activities
generation, the rate of bioeffluent generation depends on the
Activity met level of physical activity. Bioeffluent generation also depends
on personal hygiene such as the frequency of baths or showers.
Seated, quiet 1.0
Reading and writing, seated 1.0
Because both CO and bioeffluent generation rates depend on
Typing 1.1
physical activity, the concentrations of CO and the odor
Filing, seated 1.2
intensity from human bioeffluents in a space exhibit a similar
Filing, standing 1.4
Walking, at 0.89 m/s 2.0
dependence on the number of occupants and the outdoor air
House cleaning 2.0-3.4
ventilation rate.
Exercise 3.0-4.0
7.3 Experimental studies have been conducted in chambers
and in occupied buildings in which people evaluated the
acceptability of the air in terms of body odor (3-7). These
experiments studied the relationship between outdoor air
ventilation rates and odor acceptability, and the results of these
studies were considered in the development of most ventilation
standards and guidelines (including ASHRAE Standard 62).
This entire section is based on the results of these studies.
7.3.1 These studies concluded that about 7.5 L/s of outdoor
air ventilation per person will control human body odor such
that roughly 80 % of unadapted persons (visitors) will find the
odor at an acceptable level. These studies also showed that the
same level of body odor acceptability was found to occur at a
CO concentration that is about 650 ppm(v) above the outdoor
concentration.
7.3.2 Fig. 2 shows the percent of unadapted persons (visi-
tors) who are dissatisfied with the level of body odor in a space
as a function of the CO concentration above outdoors (8). This
figure accounts only for the perception of body odor and does
not account for other environmental factors that may influence
the dissatisfaction of visitors to the space, such as the concen-
trations of other pollutants and thermal parameters. Based on
the relationship in Fig. 2, the difference between indoor and
outdoor CO concentrations can be used as an indicator of the
FIG. 1 CO Generation and Oxygen Consumption as a Function 2
acceptability of the air in a space in terms of body odor and,
of Physical Activity
therefore, as an indicator of the adequacy of the ventilation rate
and CO generation rates on physical activity in units of mets to control the level of body odor. However, the relationship
for average adults with a surface area of 1.8 m . RQ is assumed
between percent dissatisfied and CO concentration is also
to equal 0.83 in Fig. 1. dependent on the personal hygiene of the occupants of a space,
6.6 Based on Eq 1 and Fig. 1, the CO generation rate
that is, their frequency of bathing, and the societal expectations
corresponding to an average-sized adult (A = 1.8 m ) engaged of the visitors to the space. The individuals involved in the
D
in office work (1.2 met) is about 0.0052 L/s. Based on Eq 1, the experiments on which Fig. 2 is based were office workers and
CO generation rate for a child (A =1m ) with a physical university students with modern habits of personal hygiene
2 D
activity level of 1.2 met is equal to 0.0029 L/s .
6.7 Eq 1 can be used to estimate CO generation rates based
on information on body surface area that is available in th
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