1、Designation: D6245 12Standard Guide forUsing Indoor Carbon Dioxide Concentrations to EvaluateIndoor Air Quality and Ventilation1This standard is issued under the fixed designation D6245; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes how measured values of indoorcarbon dioxide (CO2) concentrations can be used in e
3、valua-tions of indoor air quality and building ventilation.1.2 This guide describes the determination of CO2genera-tion rates from people as a function of body size and level ofphysical activity.1.3 This guide describes the experimentally-determined re-lationship between CO2concentrations and the ac
4、ceptability ofa space in terms of human body odor.1.4 This guide describes the following uses of indoor CO2concentrations to evaluate building ventilationmass balanceanalysis to determine the percent outdoor air intake at an airhandler, the tracer gas decay technique to estimate wholebuilding air ch
5、ange rates, and the constant injection tracer gastechnique at equilibrium to estimate whole building air changerates.1.5 This guide discusses the use of continuous monitoringof indoor and outdoor CO2concentrations as a means ofevaluating building ventilation and indoor air quality.1.6 This guide dis
6、cusses some concentration measurementissues, but it does not include or recommend a method formeasuring CO2concentrations.1.7 This guide does not address the use of indoor CO2tocontrol outdoor air intake rates.1.8 UnitsThe values stated in SI units are to be regardedas standard. No other units of me
7、asurement are included in thisstandard.1.9 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory l
8、imitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1356 Terminology Relating to Sampling and Analysis ofAtmospheresD3249 Practice for General Ambient Air Analyzer Proce-duresE741 Test Method for Determining Air Change in a SingleZone by Means of a Tracer Gas Dilution2.2 Other Docume
9、nts:ASHRAE Standard 62.1 Ventilation for Acceptable IndoorAir Quality33. Terminology3.1 DefinitionsFor definitions and terms used in thisguide, refer to Terminology D1356.3.2 Definitions of Terms Specific to This Standard:3.2.1 air change rate, nthe total volume of air passingthrough a zone to and f
10、rom the outdoors per unit time, dividedby the volume of the zone (s1,h1).43.2.2 bioeffluents, ngases emitted by people as a productof their metabolism that can result in unpleasant odors.3.2.3 single-zone, nan indoor space, or group of spaces,wherein the CO2concentration is uniform and that onlyexch
11、anges air with the outdoors.4. Summary of Guide4.1 When investigating indoor air quality and buildingventilation, a number of tools are available. One such tool isthe measurement and interpretation of indoor and outdoor CO2concentrations. Using CO2concentrations to evaluate buildingindoor air qualit
12、y and ventilation requires the proper use of theprocedures involved, as well as consideration of several factors1This guide is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.05 on Indoor Air.Current edition approved April 1, 2012. Publ
13、ished May 2012. Originallyapproved in 1998. Last previous edition approved in 2007 as D6245 07. DOI:10.1520/D6245-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to
14、 the standards Document Summary page onthe ASTM website.3Available from American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc., 1791 Tullie Circle, NE, Atlanta, GA 30329.4A common way of expressing air change rate units is h-1= air changes per hour.1Copyright ASTM Internati
15、onal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.related to building and ventilation system configuration, occu-pancy patterns, non-occupant CO2sources, time and locationof air sampling, and instrumentation for concentration mea-surement. This guide discusses
16、 ways in which CO2concentra-tions can be used to evaluate building indoor air quality andventilation.4.2 Section 6 discusses the rate at which people generateCO2and the factors that affect this rate.4.3 Section 7 discusses the use of indoor concentrations ofCO2as an indicator of the acceptability of
17、 a space in terms ofperceptions of human body odor.4.4 Section 8 describes the use of mass balance analysis todetermine the percent outdoor air intake at an air handler basedon the measured CO2concentrations in the supply, return, andoutdoor air intake airstreams.4.5 Section 9 describes the use of t
18、he tracer gas decaytechnique to determine building air change rates usingoccupant-generated CO2as a tracer gas. The tracer gas decaytechnique is described in detail in Test Method E741, and thissection discusses the application of this test method to thespecial case of occupant-generated CO2after th
19、e occupantshave left the building.4.6 Section 10 describes the use of the constant injectiontracer gas technique with occupant-generated CO2to estimateoutdoor air ventilation rates. This technique is sometimesreferred to as equilibrium analysis, and Section 10 discussesthe use of this technique and
20、the assumptions upon which it isbased.4.7 Section 11 discusses the use of continuous monitoring ofCO2concentrations as a means of evaluating indoor air qualityand ventilation in buildings. In this discussion, continuousrefers to real-time concentration measurement recorded with adatalogging device,
21、generally over several days.4.8 Section 12 discusses CO2concentration measurementissues, including measuring outdoor concentrations, samplelocations for indoor concentration measurements, establishingthe uncertainty of measured concentrations, and calibration.5. Significance and Use5.1 Indoor CO2con
22、centrations have been described andused by some people as an indicator of indoor air quality. Theseuses have included both appropriate and inappropriate inter-pretations of indoor CO2concentrations. Appropriate usesinclude estimating expected levels of occupant comfort interms of human body odor, st
23、udying occupancy patterns,investigating the levels of contaminants that are related tooccupant activity, and screening for the sufficiency of ventila-tion rates relative to occupancy. Inappropriate uses include theapplication of simple relationships to determine outdoor airventilation rates per pers
24、on from indoor CO2concentrationswithout verifying the assumptions upon which these relation-ships are based, and the interpretation of indoor CO2concen-trations as a comprehensive indicator of indoor air quality.5.2 Outdoor air ventilation rates affect contaminant levels inbuildings and building occ
25、upants perception of the acceptabil-ity of the indoor environment. Minimum rates of outdoor airventilation are specified in building codes and indoor airquality standards, for example, ASHRAE Standard 62. Thecompliance of outdoor air ventilation rates with relevant codesand standards are often asses
26、sed as part of indoor air qualityinvestigations in buildings. The outdoor air ventilation rate ofa building depends on the size and distribution of air leakagesites, pressure differences induced by wind and temperature,mechanical system operation, and occupant behavior. Given allof this information,
27、 ventilation rates are predictable; however,many of these parameters are difficult to determine in practice.Therefore, measurement is required to determine outdoor airchange rates reliably.5.3 The measurement of CO2concentrations has beenpromoted as a means of determining outdoor air ventilationrate
28、s per person. This approach, referred to in this guide asequilibrium analysis, is based on a steady-state, single-zonemass balance of CO2in the building and is sometimespresented with little or no discussion of its limitations and theassumptions on which it is based. As a result, in some cases,the t
29、echnique has been misused and indoor CO2concentrationmeasurements have been misinterpreted.5.4 When the assumptions upon which equilibrium analysisis based are valid, the technique can yield reliable measure-ments of outdoor air ventilation rates. In addition, indoor CO2concentrations can be used to
30、 determine other aspects ofbuilding ventilation when used properly. By applying a massbalance at an air handler, the percent outdoor air intake in thesupply airstream can be determined based on the CO2concen-trations in the supply, return, and outdoor air. This percentagecan be multiplied by the sup
31、ply airflow rate of the air handlerto yield the outdoor air intake rate of the air handler. Inaddition, the decay of indoor CO2concentrations can bemonitored in a building after the occupants have left todetermine the outdoor air change rate of the building.5.5 Continuous monitoring of indoor and ou
32、tdoor CO2concentrations can be used to study some aspects of ventilationsystem performance, the quality of outdoor air, and buildingoccupancy patterns.6. CO2Generation Rates6.1 Human metabolism consumes oxygen and generatesCO2at rates that depend on the level of physical activity, bodysize, and diet
33、.6.2 The rate of oxygen consumption VO2in L/s of a personis given by Eq 1:VO250.00276 ADM0.23 RQ 1 0.77!(1)where:AD= DuBois surface area m2,M = metabolic rate per unit of surface area, met (1 met =58.2 W/m2), andRQ = respiratory quotient.The DuBois surface area5equals about 1.8 m2for anaverage-sized
34、 adult and ranges from about 0.8 to 1.4 m2forelementary school aged children. Additional information onbody surface area is available in the EPA Exposure FactorsHandbook (2). The respiratory quotient, RQ, is the ratio of the5The body surface area ADin m2can be estimated from the formula AD=0.203H0.7
35、25W0.425where H is the body height in m and W is the body mass in kg (1).D6245 122volumetric rate at which CO2is produced to the rate at whichoxygen is consumed. Therefore, the CO2generation rate of anindividual is equal to VO2multiplied by RQ.6.3 Chapter 9 of the ASHRAE Fundamentals Handbook,Therma
36、l Comfort (1), contains typical met levels for a varietyof activities. Some of these values are reproduced in Table 1.6.4 The value of the respiratory quotient RQ depends ondiet, the level of physical activity and the physical condition ofthe person. RQ equals 0.83 for an average adult engaged inlig
37、ht or sedentary activities. RQ increases to a value of about 1for heavy physical activity, about 5 met. Based on the expectedvariation in RQ, it has only a secondary effect on CO2generation rates.6.5 Fig. 1 shows the dependence of oxygen consumptionand CO2generation rates on physical activity in uni
38、ts of metsfor average adults with a surface area of 1.8 m2. RQ is assumedto equal 0.83 in Fig. 1.6.6 Based on Eq 1 and Fig. 1, the CO2generation ratecorresponding to an average-sized adult (AD= 1.8 m2) engagedin office work (1.2 met) is about 0.0052 L/s. Based on Eq 1, theCO2generation rate for a ch
39、ild (AD=1m2) with a physicalactivity level of 1.2 met is equal to 0.0029 L/s .6.7 Eq 1 can be used to estimate CO2generation rates basedon information on body surface area that is available in theEPA Exposure Factors Handbook (2) and other sources.However, these data do not generally apply to the el
40、derly andsick and, therefore, the user must exercise caution whenconsidering buildings with such occupants.7. CO2as an Indicator of Body Odor Acceptability7.1 This section describes the use of CO2to evaluate indoorair quality in terms of human body odor acceptability andtherefore, the adequacy of th
41、e ventilation rate to control bodyodor. The material in this section is based on a number ofexperimental studies in both chambers and real buildings anddescribes the most well-established link between indoor CO2concentrations and indoor air quality.7.2 At the same time people are generating CO2they
42、arealso producing odor-causing bioeffluents. Similar to CO2generation, the rate of bioeffluent generation depends on thelevel of physical activity. Bioeffluent generation also dependson personal hygiene such as the frequency of baths or showers.Because both CO2and bioeffluent generation rates depend
43、 onphysical activity, the concentrations of CO2and the odorintensity from human bioeffluents in a space exhibit a similardependence on the number of occupants and the outdoor airventilation rate.7.3 Experimental studies have been conducted in chambersand in occupied buildings in which people evaluat
44、ed theacceptability of the air in terms of body odor (3-7). Theseexperiments studied the relationship between outdoor airventilation rates and odor acceptability, and the results of thesestudies were considered in the development of most ventilationstandards and guidelines (including ASHRAE Standard
45、 62.1).This entire section is based on the results of these studies.7.3.1 These studies concluded that about 7.5 L/s of outdoorair ventilation per person will control human body odor suchthat roughly 80 % of unadapted persons (visitors) will find theodor at an acceptable level. These studies also sh
46、owed that thesame level of body odor acceptability was found to occur at aCO2concentration that is about 650 ppm(v) above the outdoorconcentration.7.3.2 Fig. 2 shows the percent of unadapted persons (visi-tors) who are dissatisfied with the level of body odor in a spaceas a function of the CO2concen
47、tration above outdoors (8). ThisTABLE 1 Typical Met Levels for Various ActivitiesActivity metSeated, quiet 1.0Reading and writing, seated 1.0Typing 1.1Filing, seated 1.2Filing, standing 1.4Walking, at 0.89 m/s 2.0House cleaning 2.0-3.4Exercise 3.0-4.0FIG. 1 CO2Generation and Oxygen Consumption as a
48、Functionof Physical ActivityNOTE 1This figure applies to spaces where human bioeffluents are theonly sensory contaminants in the air.FIG. 2 Percent of Visitors Dissatisfied as a Function of CO2Concentration (8)D6245 123figure accounts only for the perception of body odor and doesnot account for othe
49、r environmental factors that may influencethe dissatisfaction of visitors to the space, such as the concen-trations of other pollutants and thermal parameters. Based onthe relationship in Fig. 2, the difference between indoor andoutdoor CO2concentrations can be used as an indicator of theacceptability of the air in a space in terms of body odor and,therefore, as an indicator of the adequacy of the ventilation rateto control the level of body odor. However, the relationshipbetween percent dissatisfied and CO2concentration is alsodependent on the personal hygiene of the o
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