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Indoor air quality assessment in an office-library building. Part I - Test
methods
Shaw, C. Y.; Magee, R. J.; Shirtliffe, C. J.; Unligil, H.
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recherche en -.
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Bev [:rei~ll~ti:lt~ ANALYSE constructionANALYZED
Indoor Air Quality
Assessment in an Officem
Library Building:
Part I Test Methods
by
C.Y. Shaw, R.J. Magee, C.J. Shirtliffe, H. Unligil
- - ~ - -
CI:STI/ICIS-,- NRc
,,-,.
Reprinted from:
I RC Ser -..NRCASHRAE Transactions 1 991
R e c e j ,vecl
Vol. 97, No.2, p. 129-1
35
IRI:: p a p e r an:r:,~-,[;lus-g-,
a(IRC Paper No.
1833)
I *
INDOOR AIR QUALITY ASSESSMENT
IN AN OFFICE-LIBRARY BUILDING:
PART
I
-TEST METHODS
C.Y. Shaw, Ph.D., P.E. R.J. Magee C.J. Shirtliffe, P.E. H. Unligil, Ph.D.
Member ASMLlE
ABSTRACT restricted to a single room on the ground floor with a
separate ventilation system. A. large amount of photowpy- A detailed investigation of the indoor air qualily (24[2) ing is performed daily in support of the building's role as of a@& air-conditioned eight-story oBice/library building a library. Most is performed on the sixth floor, where up war carried out. l?u? mainpwpose of tkinwtigation war to six photocopiers may be used continuously between 9 to d e t m ~ i n e the mu.e(s) of occupnnts' complaints, which a.m. and noon and from 2 p.m. to 4 p.m. The photocopiers included stu& air, headaches, eye immtation, a decline in were vented into the floor space.
health, and prolonged allergic reaction. The building has nine air-conditioning systems (Figure Details of the study are presented in two papers. Pari 1). Systems 1 and 2 are all-air, hvo-deck systems that serve I describes the test plan and procedures, which, while
developed specifically for this investigation, can be adapted for similar ofice building studies. Part IIpresents the study results and recommendations for remedial mearures for this building.
INTRODUCTION
As concern for air quality in office buildings has
grown, so, too, has the demand for its assessment. Evalua-
tion is, however, often hampered by the diverse and
o
U T D 00nonspecific symptoms reported by office staff and the fact A I R
that established evaluation criteria for industrial exposures 1 NTA K E
s
are not generally applicable to office environments (NIOSH F 0 R
1987). Although standards such as
ASHRSE
62-1989 L O W E R(ASHRAE
1989) provide guidelines for outdoor air re- F L O O R s quirements and exposure limits fcr office buildings, theinformation is far from complete. Furthermore, where standards exist, accepted measurement techniques for determining compliance are generally lacking. Thus, modification of existing methods-andlor development of new ones-is often required.
This is the first of two papers describing a detailed indoor air quality investigation of an eight-story officeni- brary complex, the main objective of which was to deter-
mine the cause@) of repeated wmplaints by occupants dating back to 1981. This paper presents the test methods., a second paper discusses the test d t s (Shaw et al. 1991).
TEST BUILDING
The building is a fully air-conditioned eight-story offidlibrary building in which the first four floors contain offices and the remaining four house libmy stacks. The floor area of each of the lower three floors is about 4,800
mZ and that of each of the upper five floors is about 2,400 m2. The building bas a central core area housing two passenger elevators, two stairwells, washrooms, service
shafts, study carrels, and small sitting areas. Except for the
second and third floors, the floor q a c e is fairly open, with F~gun
I
~icalfloorplonrshowing theHVAC~ystems very few individual offices. S i 1984, smokiag Las bChi Y. Shaw is a Senior Rwcanh Offar, Robert J. Magee is a Technical Officer, and Clifford J. S h i e is a Scnior Research
Officer at the I ~ t i t u t c for R w h in Construction, NationnlReaearch Council Canada. Ottawa, Ontario. Haluk H. Unligii is a Lecturer,
Faculty of ForcaWy, Dcpaltmcnt of Woad Science and Technology. Univcmity of isturbul. Turkey.
the fourth through seventh floors; system 3 is a 100% outdoor air supply-only system serving the central core area. The outdoor air intake and exhaust air openings for these
three
systems are located in the north and south walls of the mechanical room directly above the seventh floor. Systems 3 , 4 , and 8 serve the third floor, and these threeplus systems 5, 6, 7, and 9 serve the ground, first, and second floors. Two of the six systems for the lower four floors (systems 6 and 9) are induction systems and serve the perimeter wall area; the other four (systems 4, 5, 7, and 8)
are all-air, two-deck systems that serve the interior area
between the central core and
the
perimeter wall. Outdoorair
for the six lower systems comes from four intake shafts located outside the building, about 5 m above grade level, beside the northand
south walls (Figure I).AIR-QUALITY-RELATED COMPLAINTS AND PREVIOUS INVESTIGATIONS
At the request of the building management, no occupant survey was conducted. The nature and extent of occupant complaints could thus be discerned only h m interoffice memoranda supplied by the administration. These docu- ments included a formal complaint of prolonged allergic reaction and decline in health by an employee working in the southern and southeastern areas of the first floor. Several verbal complaints of stuffy air, headaches, and eye imtation were received from employees working in the fifth- ana ~ixth-flmr photowpy areas.
In an attempt to determine the cause($) of the com- plaints, two pilot studies were initiated. In the first, con- ducted in 1981, CO,, CO, ozone, and total suspended particulates on the ground, second, and third floors were measured for a two-week period. As the measured con- ccntrations were all within the limits recommendd by
ASHRAE Standard 62-1981 (-4SHRAE 1981b). uo causal
agents could be identified and, therefore, no remedial measures were re~ommended.
A second investigetian, cogducted in 1986 after complaints continued, record& concentratiors of total volztile organic compounds (TVOC) and fungal spores in addition to the contaminants measured in the 1981 study. Dust, liquid, and air samples were examined for principal components. TVOC concentrations in the complaint areas on the first and sixth floors exceed4 values found to cause complaints (Molhave et al. 1986). The main TVOC source was identified as the exhaust gas from liquid toner, transfer process photocopiers. The study was not, however, exten- sive enough to rule out other possible causes of the oc-
cupants' complaints. A third investigation, the subject of this report, was carried out between March 1987 and August 1988.
DEVELOPMENT OF ASSESSMENT PLAN
The symptoms described by the employees, the failure to identify the causal agents in the two previous studies, and the lack of clinical evidence of known building-related illness all suggest that the indoor environment of this building resembled that of "sick building syndrome" (ACGIH 1987; WHO 1983; F i e g a n el al. 1984; Hodgson
el al. 1986). An assessment plan was developed accordingly
(Shaw 19888.b). The 10-point plan (see Appendix A for a
brief description) included a thomugh check of the heating, ventilating, and air-conditioning systems. Other tasks included shldying the building's use and occupancy, identifying and measuring the air contaminants involved,
and establishing a basis for remedial measures. This plan is
,
designed for a study team consisting of an engineer, an HVAC technician, and several individuals f w a r with industrial hygiene evaluation techniques.METHODS OF MEASUREMENT
The air quality examination was dividedinto three main sections: the design and operational characteristics of the HVAC systems, the levels and sources of chemical and particulate contaminants, and the levels and sources of contaminants of biological origin. Methods for each are ' discussed below.
HVAC Systems
The
performance of the HVAC systems was assessedon the basis of air change rates, air distribution patterns, thermal comfort conditions in the occupied areas, and problems related to HVAC design, installation, and opera- tion. The methods of measurement used are discussed
below.
Air Change Rates Air change rates were masued using the tracer gas decay method. The W A C systems were set according to predetermined test conditions (for example, the outdoor air dampers were set at their mini-
mum opening positions when checking the minimum ventilation rate). A small amount of SF, tracer gas was injecled directly into thth:: supply air ducts of systems 1, 2, 6, and 9 (these systems were selected to ensure that SF, was injected directly into each story at well-distributed locations). The htal amourt of ;racer g a required was calculated from the equation:
where
m = arcountof tracer gas V = buildingvolume
C, = maximum concentration.
The maximum tracer concentration required depends on analyzer sensitivity. For the gas chromatographlelectron capture detector employed in this study, a concentration of 50 ppb was selected. With a building volume of approxi- mately 80,000 m3, the total quantity of pure SF, required was: m = 80,000 m3
.
1,000 L/m3.
50 parts SF6/109 parts air--
= 8 X lo7 L.
50 X = 4 Lpure SF,.After injection, about one hour was allowed for mixing of the tracer. An automated system was then used to collect samples from rehvn ducts at each floor. Samples from each location were continuously pumped via 4.8-mm-ID plastic tubing to a multi-position valve that automatically sent the samples, one after another, to the gas chromatograph for , analysis.
To evaluate mixing of the tracer gas with the indoor air, additional samples were collected manually at 10- minute intervals from two locatioas on each floor as follows. Just prior to the sampling time, a 60-mL syringe was purged twice with air at the test location. At the designated time, 50 mL of air was collected in the syringe
and injected into a 20-mL evacuated glass test hlbe with a rubber septum-stopper (the type used for blood sampling in medical laboratories). The pressure under which the sample was stored was later used to drive the sample into the gas chromatograph for analysis.
The air change rate. was obtained by plotting the logarithm of the measured wncentrations at each sampling location against time in hours. The data were then fitted with a straight line and the slope of the line was the air
change rate expressed in
air
changes per hour (ach). The average value of these air change rates was used as the mean air change rate of the buildink.To reduce the amount of data in subsequent measure-
ments, a manifolded sampling system (Figure 2) was used. Samples from the east and west return ducts
or
each floorwere drawn continuously through individual 4.8-mm-ID
ulastic tubes and mixed in a small manifold. A valve was
htalled in each sampling tube to set and maintain identical flow rates h m each location. The aversae air change rate was determined directly from the ~amp1& dram fi6m the manifold.
Air
Distribution For assming air distxibution within the buildine. a small amount of SF. was iniected at aparticular l k t i o n to create a point soiuce. Thi mount of tracer gas injected was similar to
t
b
t
used for air change mamremats. Immediately foUowinginjection, tracer gas samples were taken (at 10-minute intervals) at the main return ducts on each floor, at eight locations on the first and second floors, and at four locations on each of the hd, fourth, fifth, and sixth floors. Both the automated and manual sampling systems described previously were used. The tracer gas concentrations of each sapling location were then plotted against time. Figure 3 shows a typical example of such a plot, in which the concentrations at allsampling locations reached a single level in approximately 80 minuts. This time can be used to afsess the perfoz-
m a n e of the air distribution systems.
Reentrainment of Exhaust Air To d e t e d e whether exhaust air reenters the builhg, a small amount of SF6 W B ~
injected into an exhaust system and samples were then taken at the outdoor air 111take of each HVAC system using the
Figure 2 Awomated tracer gar sampling sy-stem for
mecrrwing air change rates
(HCHO), total volatile organic compounds (TVOC), and suspended and senled particulates were monitored at locations throughout the building. Some of these (e.g., Cq) were selected because they are listed id various standards as
typical indoor air pollutants. Others (e.g.,
TVOC)
were chosen based on the reaults of previous investigations in the building.All
detectors were calibrated according to manu- facturers' recommendations prior to sampling. Monitoring dstails are eiven below.~ a r b o ; Monoxide (CO) For a psriod of approximately
three months starting in August 1987, concentrations of CO were continuously monitored at the rehun duct and near the center of the occupied area on each of the seven upper floors using an infrared detector (range: 0 to 100 ppm;
< "
FIRST FLOOR SAMPUkG
~ C E P FS IWFCTED LOCATtOr4S
lmo s m w $9
5 0
m
l
syringehest tube technique.
Installation and Operational P r o b l m with RVAC Systems Visual inspeciions were made of each HVAC system to check for installation and operational problems
that cannot usually be detected by simply studying mechan- 2o ical drawinas. The flow direction of the outdoor air supply F ~rre-spon&~ to different damper settings was ch&ked 101
using smoke pencils. z
Thermal Comfort Thermal comfort was evaluated 0
according to the method o u t l i d in
ASNRCF
Standard 55- 'O81 (ASHRAE 19818). Two modes of sampling were
8
THIRD 0 LGl R L N R N W C T FLOORconducted. Smt checks at various locations were taken by
I:
wm amw DUCTrecording &om temperature (dry-bulb), mean radiant
temperahue, air velocit)l, and relative humidity. Each
pameter was m e w m i at time elevations above floor
2
level: 7 cm (ankle level), 75 cm (seated waist level), and
30
185 an. To monitor variations in thermal comfort during
office hours at several locations in the building, the probes 20
were mounted 75 cm above flnor level and values for each of the four paaxmeters were recorded at six-minute intervals for a period of six hours.
10 -/a
0 ' 3
.
Chemical Contaminants and Particulate Matter 0 20 40 TIME, min 60 80
Concentrations of carbon monoxide (CO), carbon Eigun 3 Air distribution p a n m with the tracer gas dioxide (COJ, nitrogen dioxide
pod,
formaldehyde injected into supply air ducts ofsystem 9precision: 1% full scale). Measurements on the ground floor were taken at the return duct only. One location outside the building near the roof level was also sampled to obtain a background concentration.
Carbon
Dioxide (Cod CO, uu~ceutrations were measured continuously using an infrared detector (range: 0 to 5,000 ppm; precision: 1% full scale). An automated system used for this purpose (Pigure 4) consisted of 16 sampling pumps, a 16-port multipositionsampling valve, amain sampling pump, two detectors, a data logger, and a micr~~~mputer. Samples were drawn through individual
PVC
sampling tubes.Measqements were conducted at two locations on each of the w e n upper floors: at the return duct and near the center of the occupied area. On the mound floor, measure- ments w m takGat the return duc? only. The remaining position on (he simpling
- -
valve was uscd to monitor outsideair.
Four tests were conducted under different W A C system ope&g modes to detennine the effect of air
change rate on CO, concentration. One-week measurement periods were used for the first three tests. The fourth test was limited to a single day due to occupants' complaints
caused by inadequate ventilation. For the first two tests, the
air change rate of the building was controlled manually by setting the outdoor
air
supply dampers of all HVAC systems at the 100% and 75% open positions, respectively. For the third test, the HVAC systems were operated in theautomatic mode (i.e., the outdoor air supply dampers were adjusted automatically, based on the outdoor air tempera- ture). The fourth test was conducted with all the outdoor air supply dampers set at the minimum open position. The air change rates were measured regularly during each test period (automated SF, technique), and the results were averaged to obtain the mean air change rate for the test. Maximum CO, concentrations on each test &y were determined at each test location. For tbe one-week-long tests, the five values for eacb weekday were averagm to obtain a mean maximum C02 levei, C,. The relasorship between C02 concentration and air change rate was deter- mined by plotting C , vs. m a n air change rate.
Nitrogen
Dioxide (NO3 As the outdoor air intake for system 8 was adjacent to the building's southeastern shipping and receiving dock, it was felt that vehicular exhaust could enter the butldig by this route. NO2 was monitored in the complaint area on the first floor (served by system 8) and in the outdoor air intake of system 8 using a detector utilizing the chemiluminescent method (range: 0 to 1 ppm; precision: 2.5 ppb). At both locations, levels were monitored continuously for a onemonth period.Total
Hydrocarbons
(Total Volatile Organic Com- pounds).Concentrations of TVOC were measured indirectly by contmuuously mon~toring the concentrations of total hydrocatbps using a flame ionization detector (range: 0 to 100 ppm; precision: 1% full scale). To fwilitate measure- meats, a calibration curve was producedto
convert readings in ppm-CH, to mg/m3 TVOC. This calibration curve wasobtained by comparing the detector readings with those from a three-layered sorption tube sampled at the same time and location in-the builhgand d y d by gas chromatog- raphylmass ~ t r o m e t r y (GCIMS) CTsuchiya 1988). A total
of s u midbigs to lover ihe e e o f m k m e i n t s were
obtained for this purpose.
Samples at the test building were drawn through individual sampling tubes and analyzad in real time on site. TVOCs were monitored continuously at three locations: the
Egure 4 Autonuued sampling system for CO and CO,
mearurements
photocopying area on the sixth floor, where the maximum concentration had been detected in the previous inves- tigation, and the return ducts of systems 2 and 8.
Formaldehyde (ECHO) Formaldehyde concentrations were measured at locations throughout the building, including a book-binding room, mechanical room, cata- loging area, first-floor complaint area, receiving office, printing office, conference rooms, and library stacks. Ambient (roof) HCHO levels were also monitored. Passive dosimeters, which absorbed HCHO from the surrounding air into a 1% sodium bisulfite solution, were hung from ceilings for five consecutive weekdays. Exposure was initiated on Monday morning and stopped on Saturday morning. The units thus measured the average concentration of RCHO during that period. Following exposure, the dosimeters were shipped to a laboratory for analysis by the modified chromotropic a c ~ d method.
Shorter-term formaldehyde monitoring (seven hours) was also wnducted using midget impingers filled with sodium bisulfite soiution (modified NIOSH chromotropic acid method) at several locations in the building.
Suspended Particulates Suspended particle concen- trations (number, total mass, respirable mass) were moni- tored using two aerodynamic particle sizers with a mea- suring range between 0.5 pm and 15 pm with less than 10% coincidence error (the possible error of
the
detector LJcount two or more closely spaced particles as one larger particle).
The
purpose was to determine the exposure levels within the building and to characterize the impact of HVAC systems on suspended particulates.Measurements were conducted at 29 locations, inclu- d i g the breathing zone (of a seated worker) of all com- plaint area, the breathing zone and the intake of a rehlm
air grille at dl locations with potential sources (e.g., smoking room and photocopy areas), and the exit of a supply air register of each interior HVAC system. Monitor- ing was conducted under both occupied and unoccupied conditions, with and without the W A C systems operating, to determine the individual and combined effects of oc- cupant activities and W A C operation. At each location, a minimum of 12 consecutive samples were taken, each ~ t h a 10-minute duration. In addition, at the complaint areas
and potential problem areas, 240 samples were taka during weekdays, each with a 60-minute duration. Thus "pea!C
exposure levels were, in effect, average values over a single sampling duration, while "average" exposures were the mean value of the test period.
For tests of the HVAC systems, the sensor sampling inlet was extended with streamline copper Wing to posi- tions immediately in front of supply air registers. Supply air particle levels were thus determined for automatic HVAC operation and under conditions of approximately 100%, 75%, and 50% fresh
air.
In addition, samples of the filter media (roll-typeand HEPA) were collected from the HVAC systems and examined by light microscopy.Settled Particulates Settled dust samples were col- lected from hard, glassy, or wlished metal surf8ces inside
the building usinge&& transparent adhesive tapes. Microscox slides mated with glycerine wen left.for eiaht
weeks at iarious locations to Gllect fresh samples. Samile examinations for components were made using bright field and p o l a r i d light microscopy.
Biogenic contaminants
Air and water samples from locations inside and outside the building were examined for biological contaminants
(Unligil and Shirtliffe 1991). The draft guidelines produced by the ACGM Committee on Bioaerosols were closely followed (ACGM 1987). Special attention was given to the various compartments of the HVAC systems. Settled dust samples from high- and low-traffic areas and from air
filters were also examined for biogenic air contaminants includine allereens such as ~ l a n t oollens. funeal swres. and - - A
hyphal f;agm&ts.
Aii Samoles Tw6 technioues were em~loved for collection of -microbial aerosoc samples. BO& hvolved collection of samples on nutrient agar, incubation of the exposed media at 2S°C, and subsequent counting and identification of colonies. The principal difference in the methods lay in the collection p~ocedure. The first used
centrifugal air samplers (flow rate: 40 Urnin; sampling time: 4 min), while the m a d involved settling onto 10%
mm-diameter by 15-mm-high petri plates. Th-, settling technique was employed in the library stack areas of the building. Rose bengal-streptomycin-agar (RSA) was used as the m d u m for yeasts and molds, and tryptic soy-agar (TSA) was used for the total wunt (~.e., yeasts, molds, and bacteria).
For examinations of the HVAC systems, the centrifugal samplers were used to take air samples outside the outdoor
air supply register, upstream of the air prefilters at the mixing chamhzr, upstream of the water spray unit, at the intake of the supply air f a just downstream of the water spray unit, and near the supply air registers (Figure 5). To determine the effect of aerosols generated by water spray units, sampling was conducted with the water spray unit both on and off.
Settled Dust Sampls Samples of settled particulates were examined for the presence of allergens (see above for methods of collectionand analysis). Lactophenol-containing crystal violet or cotton blue was used as a fixative and mounting medium for the detection of fungal hyphae.
Liquid Samples Samples from the reservoirs in the HVAC spray water systems were analyzed for endotoxin contamination levels. Endotoxins are constituents of the cell walls of some bacteria.
DISCUSSION
'iht tracer-gas decay technique was chosen for mea-
suring air change rates because it can be conducted by
teams without expensive tracer gas detectors, since the manually collected tracer gas samples can be sent to a laboratory for analysis. This technique is also suitable for conducting air distribution tests and tracing the movement of contaminants generated at a local source in tall buildings. For a typical 10-minute sampling interval, one person can easily take samples from five key locations on a single floor.
In checking air distribution within the building, no attempt was made to measure ventilation effectiveness, since this remsins an active research topic with a confusiing range of delinitions. Individual resawhers have not always been consistent with terminology used in its description, and
different authors have occasionally used different expres- sions to represent the m e parameter (AIVC 1987).
A combination of mechanical drawing analysis, visusl inspections, and spot measurements is needed to detect iastauation and operational problems in W A C systems. For example, an iuspection of one of this building's supply
air systems ix@atd that thdsystem performed well when it was operated at 100% outside air (i.e., outdoor air damper fully open). However, the outdoor
air
supply ratewas found to be almost zero when the damper was partially closed. The problem was caused by a combination of high fluid resistance in the supply air duct, an oversized rehun
air damper, and a powerful rehm air fan.
When sampling lines are used to bring samples to a central location for quantificationof chemical contaminants, a check should be made to ensure that the lines do not act
as a siuk or s o ~ m through absorption or desorption. This can be checked by analysis of calibration standards directly at the instrument through various lengths of sampling line. For CO and CO, measurements, the analytical differences were less than 1% for lengths of PVC sampling tube of less than 150 m. Based on the same criterion, the maximum length of tube used for collecting THC W l e s was determined to be about 60 m.
According to the ACGM Bioaerosols Committee, air sampling for biological contaminants should only be initiated after medical or clinid assessments indicate the existence of illness that is likely due to bioaerosols (ACGIH 1987). Although in this study no positive evidence existed for workplace-related illness due to biological contam- ination, tioaerosol sampling was conducted because (1) it was noted that the cooiiig tower exhaust location is n&&e outdoor air intakes of the HVAC systems, and (2) there was a formal complaint of prolonged allergic reaction.
SUMMARY
This paper describes the measurement methods under- taken to implement a plan for assessing the indoor air
Figurn 5 Dunl4ua
HVAC
system showing samplingquality of an eight-story office~library building. Included
are technioues for assessinn the ~edotmauce of HVAC systems, mkasuring chemicd and biological contaminants, and establishinn a correlation becweetl air change rate and CO, conceutraGon. Both the plan and test
dads
were applied successfully on the test building. The methods used for messuriagair
change rate andair
distribution patterns have also been applied successfully in other buildings. ACKNOWLEDGMENTSThe authors wish to thank B.M. Braceland, M. Ber- gevin, A.P. Labelle, R.E. F h d e r , and F.W. Steel of the NRC for their help during the planning and execution of the investigation. They also wish to acknowledge the wntribu- tion of Dr. Y. Tsuchiya of the
NRC
in analyzing air samples for VOC concentradtions; and W. Robertson and Drs. R. Tobin and E.P. Ewan of Health and WelfareCanada in analyzing water samples and interpreting the results.
REFERENCES
ACGM. 1987. "Guidelines for asswsment and sampling of saprophytic bioaemsols in the indoor envimment." Bioaerosols Committee. City: kmencan Conference of Governmental Industrial Hveimists.
AIVC. 1987: AIVC ~echnical'Rote 21, "A review and
bibliography of ventilation effectiveness-Definitions, measurement, design and calculation." City: h r Infiltrationand Ventilation Center, InternationalEnergy Agency.
ASHUE. 1981a.
ASHRAE
S r h d 55-81, Thermal environmental conditions for human occupancy. Atlanta: American Society of Heating, Refrigerating, and Air-Conditior!ing Engineers, Inc.ASHRAE. 1981b. ASMiAE Standard 52-i981, Ventilation for acceptable indoor air qucliv. Atlanta: American Society of Heatinz, Refrigerating, and Air-Conditioning Engineers, Inc.
ASHRAE. 1989.
ASHXAE
Standard 62-1989, Ventilation for scceptable indoor air quality. Atlanta: American Society of Heating. Refrigeratine, and Air-Conditioninn--
-
--
-
~ n ~ i n & r s , Inc.Finnegan, M.J., C.A.C. Pickering, and P.S. Burgz. 1984. "The sick building syndrome: Prevalence studies." British Medical Journal, Vol. 289, December. Hodgson, M.J., and K. Kreiss. 1986. "Building-associated
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Molhave, L., B. Bach, and O.F. Pedersen. 1986. "Human m t i o n s to low wncentrations of volatile organic com-
pounds." Environment I n t m i o n a l , Vol. 12, pp.
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&".
-.-.
NIOH. 1987. . "Guidance for indoor air quality investigations." Cincinnati, OH: National Institute for Occupational Safety and Health, Hazard Evaluations and Technical Assistance Branch.
Shaw, C.Y. 1988a. "A proposed plan for assessing indoor
air quality of non-industrial buildings." Presented at the 81st Annual Meeting of APCA, Dallas,
TX.
Shaw, C.Y. 1988b. "Indoor air quality essessment in non-industrial buildings." Proceedings, 5th Canadian Buil- ding and Construction Congress. Montreal, Quebec,
Canada.
Shaw, C.Y., R.J. Magee, C.J. Shirtliffe, and H. Unligil. 1991. "Indoor air quality assessment in an office library buildig: Part II-Test results." ASHRAE Transanions, Vol. 97, Part 2.
Tsuchiya, Y. 1988. "Volatile organic compounds in indoor air." Chemospke, Vol. 17, No. 1, pp. 79-82; R C Paper No. 1524, NRCC 28797.
Unligil, H., and C.J. Shirtliffe. 1991. "Air quality in a libraqloffice building: Microscopy of dust and micro- biological examination." IRC Internal Report. APPENDIX P.
PROPOSED PLAN
The proposed plan developed for assessing the indoor air quality consists of 10 tasks. The details are discussed below.
Task 1 -Gathering Information
Task 1 is to understand the building itself, its m m -
dings, and the concerns of the occupants about their environment. It calls for a thomugh review of the oc- cupants' concerns and a study of the building drawings, with particular attention to the HVAC systems. An occupant survey can be conducted using, for example, the NIOSH Indoor Air Quality Questionnaire. Lacking proper data on the nature of the complaints, it is often difficult to define the types and extent of physical measurements necessary to reduce the uncertainty of the final recommendations. Task 2-Walk-through Inspection
This task is to obtain additional information about the building and its environment. Efforts should be made to identify all potential sources of air contamination (e.g., comb.mtisn de-(ices, copying machines, storage rooms and contents, and open drains). The project team should also look for common signs of problem HVAC systems (e.g., unintentionally closed outdoor air supply dampers and covered supply air registers) and the factors that can adversely affect the performance of such systems (e.g., full- height partitions and improperly located thermostats and outdoor air intakes).
During the visit, temperature, relative humidity, and the degree of thermal comfort are measured at several locations, including the problem areas. Ccncentrations of C02, CO, and other contaminants may be measure* 3s
well. In addition, smoke pencils may be used to trace the airflow patterns and detecipossible &ort-circuiting between supply and return airflows. It is suggested that smoke pencil
&& k.
conducted after regular w&king hours since-some people are sensitive to the smoke.Task 3-Initial Review
The objective of this task is to analyze the information obtained in Tasks 1 and 2 rn as to develop a sampling and measuring strategy for an indepth study, if n e c e s q . An indepth investigation sbould include Tasks 4 through 9. Task 4-Measurement of Air Change Rates
Task 4 is to develop a suitable tracer gas sampling system for use with the tracer gas decay technique for measuring air change rates. The tracer gas decay technique
involves injection of a small amount of a tracer gas, SF,, into the building and measurements of the tracer gas concentrations
wi&
time. For buildings of complex sha*, the samples taken from one or two locations per floor may not be kfficient to give a good average t&r gas con- centration of the whole building because of inadequate mixing. Thus, in the first few tests, additional samples should be taken at the flwr space to ensure that the data from all sampliing locations give similar air change rates. If this is not so, floor fans can be used to impmve the mixing or additional sampling locations should be added.One way to check the adequacy of a building's ven- tilation air is to easure that its minimum
air
change rate meets the ventilation requirement recommended by pre- vailing standards, such asASHRAE
62-1989. The minimum air change rate of a building can be determined by conduc- ting four or five tests under warm weather and calm wind conditions (i.e., outdoorair
temperature higher than 15*Cand windspeed lower than 20
knh)
and setting the outdoorair
dampem at the minimum position.Task 5-Measurement of Air Distribution and Thermal Comfort
Task
5 is to collect infarmation, in addition to air change rates, for assessing the performance of HVACsystems. It involves measw6ment of air temperatures, relative humidity, and the degree of thermal comfort in several locations, including probiem areas, perimeter offices, and internal rooms. The degree of thermal comfort pives an indication of the level of the occuoants' satisfaction
k t h the environment with resgect to 'air temperature,
relative humidity, air velocity, and the mean radiant temperature.
Tracer gas is also used to determine whether exhaust air reenters the b u i l d i and how fast a contaminant (or the outdoor air) spreads f 6 m its source (point of entry)
to
otherareas. The reentrainment of exhaust air can be iietected by
injecting a small w u n t of tracer ges into an exhaust system and measuring the concenhations at the outdoor air
intake of each W A C system. If tracer gas is detected, the outlet of the test exhaust system may have to be modified or relocated. The test should be conducted under various wind directions.
Contaminant dispersion rates can be determined by injecting a small amount of tracer gas at one location and measurine the tracer eas concentrations with time at the injectionlocation and a?so at several other locations on each flwr. The faster the concentrations of various areas approach that of the injection location, the higher the dispersion rate.
In general, for areas with known contaminant sources (e.g., a designated smoking room), the dispersion rate from these areas to the surrounding rooms should be as low as
possible to prevent the contaminated air from exhausting to the surrounding rooms. On the other hand, for general offices, the dispersion rate should be as high as possible to facilitate a uniform distribution of outdoor air.
Task 6-Identification and Measurement of Contaminants
The objective of this task is to identify the major contaminants in the building and their sources and to
measure the concentrations. This can be achieved by analyzing the air (and water) samples collected from several locations inside and outside, particularly inside various compartments of the HVAC systems. Some of these measurements may have to be repeated at another season to detect seasonal pollutants.
Task 7-Interim Review
Task 7 is to identify the contaminants whose wn- centrations should be maintained below a certain level recommended by prevailiing standards. It should also enable the project
team
to determine whether other specialists are needed to assist in the investigation.Task 8-Establishment of ~elationship'between Contaminant Concentrations and Air Change Rates
The objective of this task is to establish the relationship between concentrations and air change rate4 for selected chemical and biological contaminants. These and established srandards such as ASAYRAE 62-1989 can be used to deter- mine the amount of outdoor air required to maintain the contaminants below prescribed limits if source removal is not practical. It also can be used to estimate the amount of outdoor air required to cope with any changes in certain
contamination loads. Task 9-Final Review
The task is to review the results and obtain any missing information. Follow-up measurements of selected con- taminants can also be carried out if adjustments have been made to the HVAC systems or potential contamination sources have been removed.
Task 10-Report
The report should give a brief description of the b~ilding, the nature of the compiaints, and the methods of measurement used. The results should be interpreted and presented in a manner that is easily understood by nontech- nical persons. Finally, the basis for the recommended remedial measures should also be stated.
DISCUSSION
Joe Gifford, Industrial Hygiene Deparbnent Manager,
Delta Environmental Consultants, Denver,
CO:
Was any follow-up air sampling or HVAC evaluation conducted after the recommended modifications were made? This project was implemented based on one complaint. Are b y symp-toms still persistent in the building?
