A new approach for indoor climate labeling of building materials—emission testing, modeling, and comfort evaluation

Pergamon

Atmospheric Environment Vol. 30, No. 15, pp. 2679 2689, 1996 Copyright 1996 Elsevier Science [.td Printed in Great Britain. All rights reserved 1352-2310/96 $15.00 + 0.00

1352-2310(95) 00323-1

A NEW APPROACH FOR INDOOR CLIMATE LABELING OF BUILDING MATERIALS--EMISSION TESTING, MODELING, A N D COMFORT EVALUATION* PEDER WOLKOFF National Institute of Occupational Health, Lerso Parkall6 105, DK-2100 Copenhagen O, Denmark and P E T E R A. NIELSEN Danish Building Research Institute (First received 1 July 1994 and in final form 20 June 1995)

Abstraet--A labeling system for building materials" primary emission of volatile organic compounds (VOCs) according to their impact on comfort and health has been developed and introduced in Denmark. The system unifieschemical emission testing over time (months), modeling (includinga standard room and mathematical modeling of the emission profile, when necessary), and health evaluation. As a first step, the Danish system focuses on comfort, i.e. odor annoyance and mucous membrane irritation, because of their preponderance in the sick building syndrome reporting and the absence of other relevant data on indoor air related health effects. Two design criteria have been set: the labeling system shall be easily comprehensible and at the same time operational and dynamic. The principle is to determine the time value, t(Cm), required to reach the relevant indoor air value, Cm (presently, based on odor and mucous membrane irritation thresholds), in a standard room. Odor thresholds are used because they generally are at least one order of magnitude lower than mucous membrane irritation thresholds, t(Cm) is a measure of the period of time during which a new building material may cause indoor air quality problems, unless special precautions are made. The system may also be used for singular VOCs of which a specific health endpoint has been reported. The Danish labeling system is illustrated with the emission testing and comfort evaluation of two sealants using the Field and Laboratory Emission Cell (FLEC). Copyright © 1996 Elsevier Science Ltd Key word index: Comfort, emission, building materials, health evaluation, indoor air quality, labeling, modeling, volatile organic compounds (VOCs), time value t(Cm).

1. I N T R O D U C T I O N

The first attempt to combine emission testing of building materials with a health assessment of the emitted volatile organic compounds (VOCs) using indoor relevant odor and irritation thresholds, in addition to other non-endpoint health effects, has appeared recently (Nielsen et al., 1994). Previously, Seifert (1992) has suggested a rating system of how to classify the emission of VOCs from building materials and products into three classes. He rated the emissions from a material according to their long-term effects as carcinogens, mutagens, teratogens, and allergens, in addition to short-term effects such as mucous membrane irritation and odor annoyance using a point system. However, the system did not consider the aspect of emission decay, vide infra. A French study of *This paper is no. 7 from the "Development of Healthy Building Materials" Program.

the emission profiles of consumer products has applied occupational threshold limit values coupled with modeled concentrations using a compartment °model (Person et al., 1991). The American carpet dialogue ranks the total emission of VOCs (TVOC) after 24-96 h without reference to the potential health impact (Black et al., 1991; Black, 1992) and problems related to sample inhomogeneity (Hawkins et al., 1992). The Washington State requires security for safe new buildings with regard to indoor air quality (IAQ) and demands compliance with specific air quality standards for formaldehyde, TVOC, 4-phenylcyclohexene from carpets, all of which have to reach certain standards within 30 d of installation (Black et al., 1993). Finally, USEPA has initiated the "Source Ranking Database" project with the ultimate goal of providing an overall ranking of all product classes according to their potential contribution to indoor air pollution by use of both TVOC and single VOC evaluations (Cinalli et al., 1993).

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P. WOLKOFF and P. A. NIELSEN

The ultimate goal of material emission testing is to establish the link between emission testing data and health data, so that not only building material manufacturers can produce better materials, but also that building designers and architects will be able to select the best available materials, thus reducing the probability of, e.g. discomfort problems, like the "sickbuilding" syndrome (SBS) symptoms, in particular in new buildings. The present work was prompted by a request in late 1992 from The Minister of Housing in Denmark. The primary objective was to develop an evaluation system to label building materials according to their impact on the IAQ of emitted VOCs and later other pollutants, e.g. release of mineral fibers. Such a labeling system should provide comprehensible information allowing for selection and ranking of building materials within the same product group. The overall rationale of such an activity was fourfold: (1) The primary emission of VOCs from new building materials usually declines over a time span of several months. Several field studies have indicated or proposed tentative decay periods for the predominant decay of the emission of VOCs in a new building ranging from 3 to 12 months (Farant et al., 1992; Berglund et al., 1982; Seifert et al., 1989; Wolkoffet al., 1991a), while Wallace et al. (1987) have measured half-life decay rates from 2 8 weeks. (2) VOCs may have a certain impact on deterioration of the IAQ and they may increase SBS prevalence (Wolkoff, t995). (3) Energy efficient but "sick" buildings may cost society more than is gained by energy savings. (4) The best way to control and reduce indoor air pollution of VOCs emitted from building materials is "source control" by evaluation and proper material selection (Andersen et al., 1982; Jayjock, 1993; Levin, 1992; Tucker, 1991; WHO, 1989). The major objectives of developing the Danish indoor climate labeling system were the following: • To improve and secure a better indoor air climate in buildings. • To provide a dynamic tool stimulating the development of indoor environmentally friendly materials. • To provide manufacturers and users with comprehensible information about their materials. In this way, it is possible to improve building materials, i.e. develop more indoor environmentally friendly materials and products; be able to evaluate the influence of the emission on indoor air quality; and, possibly, rank materials according to their potential impact on comfort and health (i.e. odor annoyance and mucous membrane irritation). This paper deals with the principles for chemical emission testing and labeling by use of the Field and Laboratory Emission Cell (FLEC) (Wolkoff et al., 1991b, 1995). This is demonstrated with two sealants.

2. A P P R O A C H

As a first step, it was decided to focus on odor annoyance and mucous membrane irritation, because of their preponderance in SBS reporting. Concurrently with a better understanding of building material emissions' impact on health the acceptance criteria can be changed. Health effects with no endpoints (e.g. cancer) are difficult to handle and will in the end be a political decision, which may be manipulated (Samet, 1993). Two design criteria have been set in the Danish labeling system: the system shall be easily comprehensible and at the same time operational and dynamic. The philosophy behind the approach is that the evaluation of building materials' impact on man (e.g. the perception of the IAQ) shall not only reflect the overall emission of VOCs into the indoor environment, but also consider the emission decay over time. So, the time aspect of decay of potentially irritating and odorous VOCs from new building materials has been implemented allowing for the necessary precautions (e.g. proper material selection) immediately after the period of completion, installation, or renovation where the emissions usually are high. The use of the time should decrease the probability of high exposure due to building materials and the probability of increased SBS reporting, in particular during the occupation of new buildings. The parameter of labeling is the time value, t(Cm), required to reach the indoor relevant value, Cm, presently based on either odor or irritation thresholds in a standard room; i.e. the indoor relevant value, Cmi, is the permissible concentration of VOCi in the standard room (Nielsen et al., 1994), see Table 1. Time values (t(Cm) values for different VOCs) can be determined by a visual inspection of the emission profiles of potential VOCs obtained under comparable conditions. Alternatively, estimation of the emission constants (rate decay constants and initial emission rates) of potential VOCs are required for determination of t(Cm). All materials within one product group are treated and evaluated under identical conditions, by comparison of their decay behavior in the "naked" standard room (see Table 1), thus disregarding sink effects; up-scaling should therefore be unnecessary using this approach. The time value may also allow for ranking across different types of building materials, if the test conditions are comparable (i.e. emission testing has been carried out under similar conditions (i.e. same temperature, air velocity (cm s- 1) and area specific ventilation rate (air supply of material surface, ( s - ~ per m2))).

3. A S S U M P T I O N S

The transformation of comfort and health data in the form of indoor relevant air values in a standard room with emission profile data obtained from

New approach for indoor climate labeling

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Table 1. The standard room and assumptions used in the Danish labeling system of VOC emissions from building materials Standard room a

Emission

Volume 17.4 m 3 Floor area 7 m 2 Wall area 24 m 2 Sealant area 0.2 m 2 Total area 44 m 2

Comfort and health

All materials are permitted an equal emission per square meter a The maximum permissible contribution from a material is 50%"

C=~ = permissible concentration in a standard room of a given VOCi = indoor relevant value" of VOC~ Cm~ = Codo~.,~p~= 50% of odor detection threshold (OTi) of a given VOCi

Air exchange 0.5 h -~ The emission rate is the same in Air velocity b 1-10 cm s - 1 chamber and in standard room ~

The addition of odors is hypoadditive or incomplete

Temperature 2Y~C 4- 1.5 Rel. humidity 50 _+ 2%

An additive model for irritation is applied: C m = Cirr accept: ( ~ Ci/IT i ~< 0.5) IT~ = irritation threshold of VOC~

Models applied for determination of the time value are valid at long time

"DS (1994) and Nielsen et al. (1994). b Girman (1993). c This should yield for emission processes controlled by diffusion within the material matrix. However, it is known that the evaporation controlled emission from wet products depends on the air velocity (e.g. Wolkoff et al., 1993).

e m i s s i o n testing d a t a requires a series o f a s s u m p t i o n s m u t u a l l y a g r e e d u p o n by the labeling b o a r d (cf. DS, 1994; N i e l s e n et al., 1994; W o l k o f f a n d Nielsen, 1993a). S o m e o f these are the s t a n d a r d r o o m , c e r t a i n e m i s s i o n criteria, a n d c o m f o r t a n d h e a l t h criteria as s h o w n in T a b l e 1. C o n d i t i o n s o f t h e s t a n d a r d r o o m s h o u l d also yield for the testing c o n d i t i o n s w h e n relevant, in p a r t i c u l a r t e m p e r a t u r e , relative h u m i d i t y , the air velocity (cm s - l ) a n d area specific v e n t i l a t i o n rate, f u r t h e r see T a b l e AI in the A p p e n d i x . O t h e r i m p o r t a n t a s s u m p t i o n s are t h a t o d o r intensities at the t h r e s h o l d level are c o n s i d e r e d h y p o a d d i t i v e o r that their a d d i t i o n is i n c o m p l e t e ( C o m e t t o - M u f i i z a n d Cain, 1991, 1994a) until n e w i n f o r m a t i o n has been o b t a i n e d . It a p p e a r s t h a t the overall perceived o d o r intensity o f c o m p l e x m i x t u r e s is g o v e r n e d by the o d o r intensity o f t h e s t r o n g e s t V O C a l o n e ( B e r g l u n d a n d Lindvall, 1992), b u t it h a s b e e n s h o w n also t h a t b e l o w the t h r e s h o l d m i x t u r e s m a y s u m their effects ( P a t t e r s o n et al., 1993).

corresponds to an air velocity of about 0.01 m s ~. (Higher air velocities up to 0.1 m s-~ may be relevant and are easily achieved in the FLEC with the air control unit.) The temperature was 23.0 + 1.5°C. The FLEC was cleaned according to the FLEC protocol (Wolkoff et al., 1991b) prior to each new emission testing period. After the conditioning period, the FLEC was placed on the material matrix at time 0. Duplicate air samples (1.8 () on Tenax TA were taken at appropriate time intervals. Sampling midpoints were used for calculations. Samples were thermally desorbed (Perkin Elmer ATD 400) and chromatographed (Hewlett Packard 5890) using a FID and five-point calibration of spiked Tenax TA tubes (0.1-10/~g), and integrated with Turbochrom (Perkin Elmer). Qualitative headspace analyses were carried out by thermal desorption followed by GC/MS techniques; for details see Wolkoff and Nielsen (1993a), Figs 1 and 2, and Tables 2 and 3. The overall performance of the FLEC emission testing procedure is discussed in the Appendix. 4.2. Modelin 9 The transformation of health and comfort data in the standard room (Table 1) to emission data was done as follows, using the relevant experimental conditions for the FLEC: general formula:

4. METHOD Cmi(standard room) = ERr~i x Am/(n~, x V~t), 4.1. Experimental The material specimens are sampled and installed according to previously described (Wolkoff et al., 1991b, 1995; Wolkoff and Nielsen, 1993a) or agreed upon standards by the specific manufacture confederation. The sealants were applied to a cylindrical matrix (o.d. = 33 mm, i.d. = 21 mm, depth = 10mm) in an aluminum plate (diameter = 200mm). The exposed area was 19.0cm 2. Sealant A was a one-component water-based acrylic nonelastic type. Sealant C was an elastic type ( + 7.5%) based on synthetic plastic with synthetic oil and synthetic resin, and it was oxygen hardening. In general, the material specimen was preconditioned for 24h in C L I M P A Q (Gunnarsen et al., 1994) at ambient temperature, an air exchange rate of 64 h - l , and an air velocity of 0.15 m s - 1. The emission test was carried out with the FLEC (Wolkoff et al., 1991b, 1995) (or any other climatic chamber fulfilling certain specifications (DS, 1994)). Clean and humidified (51 + 1.5% RH measured in the FLEC output) air was supplied from a FLEC Air Control Unit (Wolkoffet al., 1995) at an air flow of 300.0 + 3 mlmin -1. This

where ERmi is the maximum acceptable emission rate of material for VOCi ( m g m - Z h 1), Cmi is the indoor relevant air value of VOCi = maximum acceptable concentration of VOCi in the standard room from material (mgm 3 ) = Codor.~ccop,; this implies that Cmi = 0.5×OTi, Cm~,FLEC is the indoor relevant air value of VOC~ in the FLEC (mg m-3). Am is the area of material in the standard room (m2), ns, is the 0.5 air exchange rate in the standard room (h-l), V~, is the standard room volume (17.4m3), FLECv is the FLEC volume (3.55 x 10-5ma), FLEC ..... is the FLEC material surface area, normally 0.0177 m 2, for sealants 0.0019 m z, F L E C , is the FLEC air exchange rate (h 1), and OTi is the odor detection threshold (rag m - 3 ) of VOCi. Using the above, the following is obtained for sealants (0.2 m z): C m =

ERm × 0.2/(17.4 x 0.5).

ER m for a given VOC~ must be converted to a chamber concentration, e.g. FLEC chamber concentration (Cm,. v~zc);

2682

P. W O L K O F F and P. A. NIELSEN

8 6

17 11

5

21 22

910[ 7

n112 "14 15

92O nn ilia , ~ i n i i i l n ~

,u,m-,

I~JJJl~m~~

I

I

Sealant A

Fill

I I III

II

II

II

I

I

I

II

I I I

1

II

Ill

I

41 11 I

I

12 43

5O

2~ ~ 445B

6

44

49

48

53

Sealant C Figs 1 and 2. F L E C headspace sampling (1.8 ~) of sealants A (waterborne acrylic based) and C (artificial oil and resin based) taken 24 h after F L E C start, for V O C identification, see Tables 2 and 3, respectively. Thermal desorption: 20 min for 250°C; G C program: 20°C ~ 220~'C (at 13 min) at 4°C m i n - t increase on 50 m C h r o m p a c k SIL 19CB column (0.25 #m, i.d. 0.32 mm). it is assumed that the emission rate of VOC~ is the same in the F L E C and in the standard room (cf. Table 1). This leads to for VOCi: Cmi.rLEc{sealant) ~< 0.5 × OTi x 17.4 × 0.5 x FLECarea/(0.2 x F L E C , x FLECv) ---, C~, VLEC (sealant) ~< OTi × 1164/FLECn.

(1)

The emission profiles of selected VOCs from paints can usually be fitted to a first-order decay model without accommodating for a sink effect, but it m a y be relevant for other climatic chambers. A newly developed exponential diffusion model, in which the diffusion coefficient depends on the

concentration gradient within the material for all data (Clausen et al., 1993; Wolkoffet al., 1993), m a y be applied for materials such as carpets and sealants. Emission constants were determined by nonlinear regression of the emission data obtained over time. These were the first-order rate constant k a ( h - l ) (evaporation model) or k l/l (exponential diffusion model), where I = material thickness (mm), and the initial emission rates M0 or Fo ( p g m -2 h-a). For some of the VOCs it m a y be necessary to use a reduced data set, due to a discontinuous decay in the start. These emission constants were used, when necessary, to calculate the time value. Alternatively and in most cases, the time values should be determined by direct visual inspection of the emission profiles.

New approach for indoor climate labeling

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Table 2. Identified VOCs emitted from sealant A 24 h after start in the FLEC, their odor (Devos et al., 1990) and irritation thresholds (RDso multiplied by 0.03 (Schaper, 1993)) and divided by a factor of 40 (Nielsen et al., 1995; cf. Verhoeffet al., 1988) Indoor "environment" comfort thresholds (/~gm-3)

No.

Sealant A VOCs

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

Acetone 2-Propanol 2-Methyl-2-propanol Butanal 2-Methyl- 1-propanola ButanoP Acetic acid Butyl acetate 1,2-Ethandiol 1,2-Propanediol Butyl propionatea 2-Butoxyethanol Ethoxyacetic acid Unknown (MW = 144) 2-Ethylhexanol Nonanal b 2-(2-Butoxyethoxy)ethanoP 2-(2-Butoxyethoxy)ethanol acetatea Pentadecane

20. 21. 22. 23.

Hexadecane bis-(l-methylpropyl) malonate a bis-(1-methylpropyl) succinatea bis-(1-methylpropyl) adipate

Odor detection

Mucous membrane irritation + 40

34,670 25,700 38,900 28 2570 1510 360 930 Supposed to be high¢ Supposed to be highc

41,846

2240 4124 2876 300 2600 3250

1660

10,222

1320 13 6800 2290 ~

1753

No response observed in mouse bioassayf 900 ~ 960 d 1080d

Major VOC after 24 h. b Possible analytical artifact. c Rowe and Wolf (1982). a Default odor threshold ( = 100 ppb). e Based on 2-butoxyethyl acetate. f Schaper (1993).

a

The time value can be determined from the emission constants which were obtained by use of the exponential diffusion model as shown by Clausen et al. (1993). The relation is valid for high air exchange rates, which is the case in the FLEC: t(Crni, r'l.Ec) = FLECarea/(Cmi × FLECv × FLECn × (k/I) - 1/(Fo × (k/l))

for t ~> 1/FLEC,,

where Fo is the initial emission rate (mg m - z h - 1) for VOC~, k/l = rate constant//( = thickness) (h- 1m - 1) for VOCi, all determined from the nonlinear regression analysis.

air velocities) as a first approximation; see Wolkoff et al. (1993). This, however, does not apply to thin-film materials, like paints, which primarily emit by evaporation. In their case, only the ranking order would be valid. The principle of labeling is the criterion that a material obtains its time value for labeling by use of its longest t(Cm) value. The best material in a comparison is that which reaches all its Cm values, based on their indoor relevant odor threshold values, within the shortest time for all relevant VOCs emitted. Thus, the time value is used in the Danish indoor climate labeling system.

4.3. Principles for t(Cm) determination and labelin 9 Dominating and persistent VOCs at long time (i.e. slow decaying emission profiles) having low Cm values based on comfort data like odor thresholds (e.g. Devos et al., 1990), mucous membrane irritation thresholds (Bos et al., 1992; Schaper, 1993) and occupational threshold limit values (Arbejdstilsynet, 1994; Nielsen et al., 1995) are selected for the determination of t(Cm) values. The selection of potentially irritative and odorous VOCs is based on the initial headspace analyses and comfort data available. A tentative "default" odor threshold of 100ppb (based on the distribution of thresholds, Devos et al., 1990) was applied in cases where the odor threshold was unavailable. Those time values, obtained from materials primarily emitting by diffusion (i.e. thick films), should correspond to real time in the standard room, because the emission rate should not be too sensitive to different air exchange rates (or

5. E X A M P L E

The labeling a p p r o a c h will be illustrated here with sealants A and C taken from Wolkoff and Nielsen (1993a). The headspace analyses of the sealants taken 24 h after F L E C start are s h o w n in Figs 1 and 2 and the evaluation thereof in Tables 2 and 3, respectively. The c o r r e s p o n d i n g emission profiles for selected V O C s emitted have been measured up to 8 months. These are s h o w n in Figs 3 and 4. Tables 4 and 5 list relevant Cm values, the c o r r e s p o n d i n g emission constants, and time values. The headspace analyses of sealants A and C, taken 24 h after start in the F L E C , showed 23 V O C s and 18 VOCs, respectively.

P. W O L K O F F and P. A. NIELSEN

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Table 3. Identified VOCs emitted from sealant C 24 h after start in the FLEC, their odor (Devos et aL, 1990) and irritation thresholds (RDso multiplied by 0.03 (Schaper, 1993)) and divided by a factor of 40 (Nielsen et al., 1995; cf. Verhoeff et al., 1988) Indoor "environment" comfort thresholds (/*gm 3) Sealant C VOCs

No. 1. 41. 42. 43. 6. 26. 27. 44. 45. 46. 47. 48. 49. 50. 51.

Acetone Hexane" Methylcyclopentane Cyclohexane Butanol Toluene Hexamethylcyclotrisiloxane Nonane Ethylbenzene Xylene Decane Ethyltoluene Trimethylbenzene 2-Ethylhexanol" Dodecane

52. 53.

Phenol Dimethyloctanols b' " 2-(2-Butoxyethoxy)ethanol"

17.

Odor detection

Mucous membrane irritation + 40

34,670 79,430

41,846 (2250 based on TLV e)

77,630 !510 5880

17,250 (based on TLV °) 2876 9510

6760 13 1410 4370

244,258 4655 4308 50% response not reached d

780 1318 14,450

3000 (based onTLV °) 1753 50% response not reached for undecane d 479

430 120 ~ 680 ~

a Major VOC after 24 h. b Sum of six isomers. c Default odor threshold ( = 100 ppb). d Schaper (1993). e Arbejdstilsynet (1994).

Sealant A

~g/m 3

10000 8000

pg/m 3 1400~

J

o Butanol 2-(2-butoxyethoxy)efhanol . ~ 2-(2-butoxyethoxy)efhanol acetafe q~, odour/aecep~

m

D

"

"'",, 6000

Sealant C

120° i

o Hexane

1000 I

• 2-ethyl-1 -hexanol 5, 7-dimethyl-octanol

800~

C~ , odour/occept

'L.

600~%

4000

4oo ~__.~_.

~ ........iiii~:::;~. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2000

:'~:

...................................

-:::::=:= .........

.,=:z

.........

..................~....... th...... -'~'o--r-- = . ,...............T--I 0 1000 2000 3000 4000 5000 6000 hours Ik

2oo

[]

.........

.......

..................

....... i - - - i

0

1000

2000

3000

4000

5000

6000 hours

Figs 3 and 4. FLEC emission profiles of selected potential VOCs emitted from sealant A (Fig. 3) and C (Fig. 4), respectively. The exposed area was 19.0 cm / (i.d. = 44 ram, o.d. = 68 mm, and depth = 10 mm). Air samples (1.8 #) were sampled on Tenax TA, followed by thermal desorption (20 min at 250°C) and gas chromatography (50m Chrompack SIL 19CB column, i.d. 0.32 mm and film thickness 0.2#m, GC temperature program: 20°C (2 rnin) --+ 220°C (13 min) with 4°C m i n - 1 increase). All measurements were in duplicate, open and closed marks, respectively. Dimethyloctanol is the sum of six isomers.

Some of the emitted VOCs exhibited a discontinuo u s d e c a y d u r i n g the first 2 - 4 weeks. This can be r a t i o n a l i z e d in t e r m s o f time to establish a c o n c e n t r a tion g r a d i e n t w i t h i n t h e m a t e r i a l o r the f o r m a t i o n of VOCs by chemical reactions during hardening. Data

r e d u c t i o n is t h e r e f o r e r e q u i r e d for d e t e r m i n a t i o n o f s o m e of the e m i s s i o n c o n s t a n t s . T h e relevant V O C for s e a l a n t A was 2 - ( 2 - b u t o x y e t h o x y ) e t h a n o l a n d for sealant C it was a m i x t u r e o f i s o m e r i c d i m e t h y l o c t a n o l s . In b o t h cases, the i n d o o r r e l e v a n t value, Cm (in this

New approach for indoor climate labeling Table 4. Emission profile constants and Sealant A FLECoow = 300 ml min- 1

t(Cm)

2685

values for sealant A

Cmi Crm,FLEC kl/l F0 (/lgm -3) (/igm -3) ( h - l m -1) (mg(m-2xh-1))

6. Butanol 17. 2-(2-Butoxyethoxy)ethanol

18. 2-(2-Butoxyethoxy)ethanol acetate

755

Corr. r2

340 b

3471 1563

6.55E -- 4a I.IE -- 5a

6.96 100.5

0.9235 0.9873

1145c

5264

7.72E - 5a

28.43

0.9971

t(Cm) (months)

~0 7.3 6.8d t0

Reduced data set applied, data between 400 and 3000 h. b Default indoor relevant odor threshold. c Based on 2-butoxyethyl acetate. a Determined by visual inspection of Fig. 3.

Table 5. Emission profile constants and Sealant C FLECflow = 300mlmin i 41. Hexane 15. 2-Ethylhexanol 53. Dimethyloctanols ~

t(Cm)

values for sealant C

Cmi Cmi,FLEC kl/I (pgm -3) (#gm -3) ( h - l m -t) 1102 659 60b

5062 3030 276

5.98E - 4 c 2.70E - 2c 1.418E -- 4 ~

Fo (mgm 2h-~)

Corr. r2

t(Cm) {months)

12.94 0.51 5.92

0.9386 0.8624 0.9151

~ 0 < 1d 2.20

a It is assumed that the isomeric dimethyl octanols can be added together. b Default indoor relevant odor threshold. c Reduced data set applied, between ca. 250 and 3000 hours. d Determined by visual inspection of Fig. 4.

case Codor/accept),was based on default odor thresholds. Therefore, the time values must be considered with appropriate caution until better data are available. It is seen from Fig. 4 that the emission profile of dimethyloctanol reached the converted Cm concentration in F L E C (Cm,FLEC) after 1500 h. Figure 3 shows that after 1500 h the CFLEC concentration of 2-(2butoxyethoxy)ethanol was about 5000 # g i n - 3 and it had not reached the indoor relevant F L E C converted Codor/accept concentration value (1563 #g m - 3) before about 4700 h, which equals 6.8 months. The t(C,O value has also been determined from the emission constants to be 7.3 months, assuming that the emission profile followed the exponential diffusion model. The Cm,FLEC concentrations of butanol and 2-(2-butoxyethoxy)ethanol acetate, respectively, had been reached within less than 100 h, see Fig. 3. Thus, sealants A and C are labeled 7 and 2 months, respectively. Assuming that the best sealant is the one reaching Cm for all potential V O C s at the shortest time, the following ranking order of increasing t(Cm) value was obtained: C < A. This ranking should be taken cautiously, for instance because real odor detection thresholds were not available for the critical VOCs. Provided that the technical specifications are fulfilled for both sealants the labeling system allows for selection of the one with a low emission of superfluous V O C s and therefore a minimum of exposure and possibly also a minimum of I A Q problems during the period of hardening caused by the VOCs.

6. DISCUSSION The first example using modeling to determine the necessary time to reach a certain emission rate of VOCs from waterborne paints was developed and used for ranking purposes by Clausen et al. (1991). In the present work, it has been shown that the time required to reach an indoor relevant odor threshold concentration, Cm, can be determined by visual inspection of the emission profile or modeling thereof. The latter, however, may not always be the case (Wolkoff, 1995). The system does not require full-scale testing, because all the emissions of materials within one product group are compared in a "naked" standard room. Ideally, the emission profiles should be independent of the climatic chamber applied for emission testing provided the air velocity (cf. Girman0 1993), area specific ventilation rate, chamber sink and chamber concentration, and V O C recovery are all under control. At present, the sorption properties of the materials are not considered. Generally, odor thresholds are magnitudes lower than mucous membrane irritation thresholds; the lower the odor threshold for a VOC, the wider the gap between its odor and irritation threshold (Cometto-Muhiz and Cain, 1994a, b). The average ratio between vapor-phase irritation and odor threshold concentrations is about 450 for 85 VOCs and inorganic volatiles when using the lowest reported RDso values (Bos et al., 1992) multiplied by 0.03 (Schaper, 1993) and the evaluated odor detection

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thresholds by Devos et al. (1990). This is compatible with a ratio of 285 found for a series of alcohols, esters, and ketones (Cometto-Mufiiz and Cain, 1993). This implies that t(Cm) values based on indoor relevant odor thresholds, in general, might secure against mucous membrane irritation, insofar as irritants act in an additive manner (Cometto-Mufiiz and Cain, 1991; Molhave and Nielsen, 1992; Nielsen et al., 1988) and odors, at threshold level, are hypoadditive (Berglund and Lindvall, 1992). It is also possible that the use of indoor relevant odor thresholds may secure against other health effects; however, this would require a detailed toxicological analysis of many VOCs. Disregarding the hedonic qualities of the emission, it is the assumption that the compiled odor thresholds (Devos et al., 1990) are operational until a better comfort endpoint has been developed, and well knowing that the single quoted thresholds may have a large range. One has to be aware of the limitations and pitfalls of such a system based on several assumptions (Wolkoff and Nielsen, 1993a; Wolkoff, 1995). Some of these are: (a) Limitation of the sorbent capacity, in particular when trapping important VVOCs. The choice of sorbent then becomes important (Bayer, 1994), alternatively cooled trapping. (b) Emission chamber performance is another important factor determining the emission. Pitfalls could be low VOC recovery, a large chamber wall sink effect, and inadequate overall analytical sensitivity (see the Appendix). Testing should ideally be performed at realistic air velocities, when relevant, and optimally at realistic area specific ventilation rates, further see Table A1 in the Appendix. To make sure that the emission mechanism has been identified, models should be evaluated at different air velocities (Guo, 1993). Even if a proper model has been identified, there are many factors which may obstruct the modeling of primary emission decays, in particular after a long time (Wolkoff, 1995). It is anticipated that for some materials, long-term emission testing will be the only way, in particular, if the emission is secondary in nature (e.g. desorption, decomposition, hydrolysis). (c) The system does not take into account the hedonic properties of the emission, only the odor intensity. The hedonic properties of the material emission may be evaluated by the use of combined GC/sniffing techniques (Jensen et al., 1995) or by panel evaluation (Gunnarsen et al., 1994). (d) Hyperadditive phenomena may occur, e.g. for odors (Arctander, 1969; Ohloff, 1994). This should be dealt with by panel evaluation, however, no generally accepted standard procedure is yet available. Considerable additivity of VOC mixtures has been suggested (Cometto-Muffiz and Cain, 1994b; Patterson et al., 1993); e.g. Ahlstr6m et al. (1986) found that mixing of formaldehyde to the air from a sick building strongly influenced the perception of poor IAQ. Such phenomena should be studied by how anosmics and normosmics perceive mixtures or by use of the mouse bioassay (Nielsen et al., 1996; Wolkoff et al., 1991c). Presently, a large number of irritation thresholds are

based on the mouse bioassay. Bos et al. (1992) have discussed the limitations of this method. (e) It is assumed that perceived odor intensity decreases by adaptation, however, perceived irritation intensity may increase with time, depending on the concentration level and composition. In a 4 h human exposure study, irritation intensity appeared to increase for about 2 h at a 24 mgm 3 TVOC level, but for only about 30min at a 6 m g m 3 TVOC level before reaching asymptotic level (Hudnell et al., 1993). However, the levels were about one order of magnitude greater than normally encountered indoors. (f) Lack of comfort data and other relevant health data can be circumvented by selective use of raw materials only emitting VOCs with known comfort thresholds and other relevant health endpoints, like cancer based on a life risk of 10 4 (Andersen Nexo, 1995). Mucosal irritation thresholds, which might be considered as upper odor thresholds, can reasonably be obtained from occupational threshold limit values by division with a factor 40, which account for 24 h of exposure 360 d a year including a safety factor of 10 (Nielsen et al., 1995). However, in the long run, methods for the determination of odor thresholds of unknown VOCs should be developed. The odor detection thresholds evaluated by Devos et al. (1990), presumably are 50-75% of the thresholds (determined by sniff testing from, e.g. squeezing bottles, cf. Cometto-Mufiiz and Cain, 1993). A future strategy to secure odor-sensitive individuals (e.g. hyperosmia), but also taking into account the usual flatness of odor stimulus-response functions (Cometto-Mufiiz and Cain, 1991), would be the use of Cmi values which represent only 10% of the reported odor detection thresholds. This would, to some extent, protect against the uncertainty of some of the reported odor thresholds. The dynamicity of the system is that the criterion for obtaining a label, based on the time value, after some time gradually can be changed to lower and lower time values on mutual agreement within the specific confederation of industries. Each product group of manufacturers has to prepare a dedicated product standard including, e.g. preconditions of material and a criterion for obtaining label of material. Because of the fact that the perception of odors is generally considered to be hypoadditive or the addition may be incomplete, it cannot be ruled out that the removal of one or two dominant odorous VOCs may result in new odorous sensations. In such a case, the entire approach should be repeated starting with the chemical emission testing identifying the potential VOCs. In addition, the system has built in a safety procedure for sensory testing over time, thus providing sensory emission profiles (intensity and acceptability) by the use of a C L I M P A Q chamber and a panel of judges (Gunnarsen et al., 1994; Wolkoff and Nielsen, 1993b). At present, it is recommended to perform the evaluation at approximately the same time as the chemically determined time value.

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7. CONCLUSION

REFERENCES

The first step towards a unified labeling system of building materials' emission of primary V O C s has been developed entirely dedicated to the indoor environment. Secondary emission of adsorbed V O C s has not been dealt with. The system has so far focused only on the two most frequently reported SBS symptoms, o d o r annoyance and mucous membrane irritation. The system is based on several assumptions which will require validation and identification of the limitations of the entire approach. The major assumptions are that odor intensities are hypoadditive and the perceived odor intensity is governed by the strongest smelling VOC, however, not accounting for the hedonic properties. This leads to the fact that the emitted VOCs can be evaluated on a single c o m p o u n d basis (for the sake of identifying undesirable VOCs). Indoor relevant o d o r thresholds are usually much lower than their corresponding mucous membrane irritation thresholds. Therefore, the use of evaluated odor detection thresholds is not only operational, in addition it is likely to safeguard against the probability of increased mucous membrane irritation caused by building material emission. The aspect of adaptation of perceived odor intensity, acceptability, and irritation (Gunnarsen and Fanger, 1992; Hudnell et al., 1993) then becomes less important in this approach. The emission profiles of two sealants showed both qualitative and quantitative differences. Health data were not available for all identified VOCs. Therefore, the assessment and established ranking order for each material type should be considered accordingly until further information becomes available about the impact on IAQ of these VOCs. In addition, the study showed that the comparison of the emission profiles requires a thorough knowledge of the material's chemistry and those factors influencing the emission rate. The system could also be applied to single V O C s of which specific health endpoints are known. The Danish labeling system is now in use on a voluntary basis. Several branches within the Danish Confederation of Industries have now prepared dedicated product standards. The system is sufficiently dynamic, so new knowledge and better understanding of the sensory perception will be implemented. It is the plan that other emission properties shall be implemented in the future. In addition, continuing research activities are ongoing to improve the system, including methods for the determination of oxidative degradation (Jensen et al., 1994), fiber release, the importance of air velocity, and principles of health evaluation.

Ahlstr6m R., Berglund B., Berglund U. and Lindvall T. (1986) Formaldehyde odor and its interaction with the air of a sick building. Envir. Int. 12, 289-295. Andersen I., Seedorff L. and Skov A. (1982) A strategy for reduction of toxic indoor emissions. Envir. lnt. 8, 11 16. Andersen Nexo B. (1995) A view on risk assessment methodologies for carcinogenic compounds in indoor air. Scand. J. Work Envir. Hlth. 21 (in press). Arbejdstilsynet (1994) Graensevaerdier for stoffer og materialer. At-anvisning, no. 3.1.0.2. Arbejdstilsynet, Copenhagen 0. Arctander S. (1969) Perfume and flavor chemicals. Idem, Montelair, New Jersey, U.S.A. Bayer C. W. (1994) Advances in trapping procedures for organic indoor pollutants. J. Chromat. Sci. 32, 312-316. Berglund B. and Lindvall T. (1992) Theory and method of sensory evaluation of complex gas mixtures. Ann. N.Y. Acad. Sci. 641, 277-293. Berglund B., Johansson I. and Lindvall T. (1982)A longitudinal study of air contaminants in a newly built preschool. Envir. Int. 8, 111 115. Black M. S. (1992) Measuring the TVOC contributions of carpet using environmental chambers. In N A T O / C C M S

Acknowledgements--This work was supported by the National Agency for Trade and Industry and the National Agency for Housing and Building. We thank Mrs B. Kvamm and Mr K. Larsen for skilful technical assistance, and Mr P. A. Clausen for help with the modeling. We thank our industrial partners for material specimens and fruitful discussions,

Pilot Study on Indoor Air Quality - - Sampling and Analysis of Biocontaminants and Organics in Non-lndustrial Indoor Environments (edited by Pierson T. K. and Naugle D. F.),

pp. 57 67. Research Triangle Institute, Research Triangle Park, North Carolina. Black M. S., Pearson W. J. and Work L. M. (1991) A methodology for determining VOC emissions from new SBR latex-backed carpet, adhesives, cushions, and installed systems and predicting their impact on indoor air quality. In Healthy Buildings '91, ASHRAE, Atlanta, pp. 267-272. Black M. S., Pearson W. J., Brown J. and Sadie S. (1993) Material selection for controlling IAQ in new construction. In Proc. 6th Int. Conf. on Indoor Air Quality and Climate, Helsinki, Vol. 2, pp. 611-616. Bos P. M. J., Zwart A, Reuzel P. G. J. and Bragt P. C. (1992) Evaluation of the sensory irritation test for the assessment of occupational health risk. Crit. Rev. Toxicol. 21,423-450. Cinalli C. A., Johnston P. K., Koontz M. D., Girman J. R. and Kennedy P. W. (1993) Ranking consumer/commercial products and materials based on their potential contribution to indoor air pollution. In Proc. 6th Int. Con/: on Indoor Air Quality and Climate, Helsinki, Vol. 2, pp. 425 430. Clausen P. A., Wolkoff P., Holst E. and Nielsen P. A. (1991) Long term emission of volatile organic compounds from waterborne paints. Methods of comparison. Indoor Air l, 562 576. Clausen P. A., Lauersen B., Wolkoff P., Rasmusen E. and Nielsen P. A. (1993) Emission of volatile organic compounds from a vinyl floor covering. In Modeling oflndoor Air Quality and Exposure (edited by Nagda N. L.), pp. 3 13. American Society for Testing and Materials, Philadelphia. Cometto-Mufiiz J. E. and Cain W. S. (1991) Influence of airborne contaminants on olfaction and the common chemical sense. In Smell and Taste in Health and Disease pp. 765 785 (edited by Getchell T. V. et al.). Raven Press, New York. Cometto-Mufiiz J. E. and Cain W. S. (1993) Efficacy of volatile organic compounds in evoking nasal pungency and odor. Archs. Envir. Hlth. 48, 309 314. Cometto-Muftiz J. E. and Cain W. S. (1994a) Sensory reactions of nasal pungency and odor to volatile organic compounds: the alkyl benzenes. Am. lnd. Hy 9. Ass. J, 55, 811-817. Cometto-Mufiiz J. E. and Cain W. S. (1994b) Perception of odor and nasal pungency from homologous series of volatile organic compounds. Indoor Air 4, 140 145.

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Danish Standard (DS) (1994) Direction for determination and evaluation of the emission from building products, pp. 1-38. Dansk Standard, DS/INF 90. Hellerup, Denmark (in Danish). De Bortoli M., Kn6ppel H., Pecchio E., Schauenburg H. and Vissers H. (1992) Comparison of Tenax and Carbotrap for VOC sampling in indoor air. Indoor Air 2, 216-224. Devos M. et al. (1990) Standardized Human Olfactory Thresholds, pp. 1-165. IRL Press at Oxford University Press, Oxford. Farant J.-P., Baldwin M. E., Repentigny F. and Robb R. (1992) Environmental conditions in a recently constructed office building before and after implementation of energy conservation measures. Appl. occup, envir. H y9. 7, 93 100. Girman J. R. (1993) Simple modeling to determine appropriate operating conditions for emission testing in small chambers. In Modeling of Indoor Air Quality and Exposure (edited by Nagda N. L.), pp. 145-148. ASTM, STP 1205, Philadelphia. Gunnarsen L. and Fanger P. O. (1992) Adaptation to indoor air pollution. Envir. Int. 18, 43 54. Gunnarsen L., Nielsen P. A. and Wolkoff P. (1994) Design and characterization of the CLIMPAQ, chamber for laboratory investigations of materials, pollution and air quality. Indoor Air 4, 56-62. Guo Z. (1993) On validation of source and sink models: problems and possible solutions. In Modeling of Indoor Air Quality and Exposure (edited by Nagda N. L.), pp. 131-144, ASTM, STP 1205, Philadelphia. Hawkins N. C., Luedtke A. E., Mitchell C. R., LoMenzo J. A. and Black M. S. (1992) Effects of selected process parameters on emission rates of volatile organic chemicals from carpet. Am. Ind. Hyg. Ass. J. 53, 275-282. Hudnell H. K., Otto D. A. and House D. E. (1993) Time course of odor and irritation effects in humans exposed to a mixture of 22 volatile organic compounds. In Proc. 6th Int. Conf. Indoor Air Quality and Climate, Helsinki, Vol. 1, pp. 567-572. Jayjock M. A. (1993) Back pressure modeling of indoor air concentrations from volatilizing sources. Am. lnd. Hyg. Ass. J. 55, 230-235. Jensen B., Wolkoff P. and Wilkins C. K. (1994) Characterization of linoleum. Part 3. Identification of oxidative emission processes. In Healthy Buildings '94, Budapest, Vol. 1, pp. 243-246. Jensen B., Wolkoff P. and Wilkins C. K. (1995) Characterization of linoleum. Part 2: preliminary odour evaluation. Indoor Air 5, 44 49. Levin H. (1992) Controlling sources of indoor air pollution. In Chemical, Microbiological, Health and Comfort Aspects of Indoor Air Quality--State of the Art in SBS (edited by Kn6ppel H. and Wolkoff P.), pp. 321 341. Kluwer Academic Publishers, Dordrecht. M~lhave L. and Nielsen G. D. (1992) Interpretation and limitations of the concept "total volatile organic compounds" (TVOC) as indicator of human responses to exposures of volatile organic compounds (VOC) in indoor air. lndoor Air 2, 65 77. Nielsen G. D., Kristiansen U., Hansen L. F. and Alarie Y. (1988) Irritation of the upper airways from mixtures of cumene and n-propanol. Archs. Toxicol. 62, 209-215. Nielsen P. A. et al. (1994) Health-related evaluation of building products based on climate chamber tests. Indoor Air 4, 146-153. Nielsen G. D., Alarie Y., Poulsen O. M. and Andersen Nexo B. (1995) Possible mechanisms for the respiratory tract of noncarcinogenic indoor-climate pollutants and bases for their risk assessment. Scand. J. Work Envir. Hlth. 21, 165--178. Nielsen G. D., Hansen L. F., Hammer M., Vejrup K. V. and Wolkoff P. (1996) Chemical and biological evaluation of building material emissions. I. A screening procedure based on a closed emission system, lndoor Air (accepted for publication).

Ohloff G. (1994) Scent and Fragrances- The Fascination o/ Odors and their Chemical Perspectives. Springer, Berlin. Patterson M. Q., Stevens J. C., Cain W. S. and ComettoMufiiz J. E. (1993) Detection thresholds for an olfactory mixture and its three constituent compounds. Chem. Senses 18, 723-734. Person A., Laurent A.-M., Festy B., Anguenot F., Aigueperse J, and Hardy S. (1991) Impact atmospherique des compos6s organiques volatils (COV) g+n6r6s dans l'habitat par les produits ~i usage domestique: charact6ristation des ~missions et mod61isation de l'exposition. Pollution Atmosph~rique Avril-Juin, pp. 159-176. Rowe V. K. and Wolf M. A. (1982) Glycols. In Party's Industrial Hygiene and Toxicology, 3rd Revised Edn, Vol. IIC, pp. 3817 3908. Wiley-Interscience, New York. Samet J. M. (1993) Indoor air pollution: a public health perspective. Indoor Air 3, 219 226. Schaper M. (1993) Development of a database for sensory irritants and its use in establishing occupational exposure limits. Am. Ind. Hyg. Assoc. J. 54, 488-544. Seifert B. (1992) Guidelines for material and product evaluation. Ann. N.Y. Acad. Sci. 641, 125-136. Seifert B., Mailahn W., Schultz C. and Ullrich D. (1989) Seasonal variation of concentrations of volatile organic compounds in selected German homes. Envir. Int. 15, 397-408. Tucker W. G. (1991) Emission of organic substances from indoor surface materials. Envir. lnt. 17, 357-363, Verhoeff A. P., Suk J. and Van Wijnen J. H. (1988) Residential indoor air contamination by screen printing plants. Int. Archs. occup, envir. Hlth. 60, 201 209. Wallace L. A., Jungers R., Sheldon L. and Pellizzari E. D. (1987) Volatile organic chemicals in 10 public-access buildings. In Proc. 4th Int. Conf Indoor Air Quali~' and Climate, Berlin, Vol. 1, pp. 188-192. Wolkoff P. (1995) Volatile organic compounds--sources, measurements, emissions, and the impact on indoor air quality. Indoor Air Suppl. 3, 1-73. Wolkoff P. and Nielsen P. A. (1993a) Indoor climate labeling of building materials--chemical emission testing, tongterm modeling, and indoor relevant odor thresholds, pp. 1-81. National Institute of Occupational Health, Copenhagen, Denmark. Idem (1993b) Indoor climate labeling of building products. Part 2: scientific and technical documentation of a prototype, pp. 1-90. Danish Building Research Institute, Horsholm (in Danish). Wolkoff P., Clausen P. A., Nielsen P. A. and Molhave L. (1991a) The Danish twin apartment study; Part I: formaldehyde and long-term VOC measurements. Indoor Air 1, 478 490. Wolkoff P., Clausen P. A., Nielsen P. A., Gustafsson G., Jonsson B. and Rasmusen E. (1991b) Field and laboratory emission cell: FLEC. In Healthy Buildings '91, ASHRAE, Atlanta, pp. 160-165. Wolkoff P., Nielsen G. D., Hansen L. F. et aL (1991c) A study of human reactions to building materials in climatic chambers. Part II: VOC measurements, mouse bioassay, and decipol evaluation in the 1 2 mg/m 3 TVOC range. Indoor Air 1, 389 403. Wolkoff P., Clausen P. A., Nielsen P. A. and Gunnarsen L. (1993) Documentation of field and laboratory emission cell "FLEC" - - identification of emission processes from carpet, linoleum, paint, and sealant by modeling. Indoor Air 3, 291 297. Wolkoff P., Clausen P. A. and Nielsen P. A. (1995) Application of field and laboratory emission cell "FLEC"--performance study, intercomparison study, and case study of damaged linoleum, lndoor Air 5, 196-203. World Health Organization Air Quality Guidelines for Europe (1987) WHO Regional Publications, European Series No. 23, World Health Organization, Copenhagen. World Health Organization Indoor Air Quality: Organic Pollutants (1989) EURO Reports and Studies No. 111. World Health Organization, Copenhagen.

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Table A1. Comparison of the area specific ventilation rate in a standard room with the FLEC and a small chamber

Standard room and chambers

Area specific ventilation rate (fs -1 m 2) (air velocity, cm s - ~)

Standard room" (17.4 m a, AER b = 0.5 h-1 ): Floor area = 7 m 2 Wall area = 24 m 2 Sealant area = 0.2 m 2

0.4 0.1 12.1

FLEC: AER = 514/4800 c h - 1: Area: floor, wall = 0.0177 m 2 Area: sealant = 0.0019 m z

(1/10) 0.3/1.3 2.6/12.3

Small chamber (50 f, AER = 0.5 h - 1): Loading = 0.41 (e.g. flooring material)

( ~ 0.005)" 0.3

a DS (1994) and Nielsen et al. (1994). bAER = air exchange rate (h-1). c This corresponds to a FLEC air supply of about 3 E m i n - ~. d Assumption that the chamber is a cube.

APPENDIX A

In general, one of the important performance criteria of emission testing with climatic chambers is the recovery of important VOCs and the overall sensitivity of the emission testing method. In addition, limitation of the VOC spectrum (very volatile to semi-volatile) is controlled by the sorbent applied. Tenax TA is a good sorbent with a low background build-up (De Bortoli et al., 1992) and a high upper boiling point VOC limit. Sampling of, in particular, VVOCs requires careful handling (e.g, cooled trapping) or an alternative choice of sorbent (Bayer, 1994). Salient climatic chamber parameters, which control the emission rate, are the temperature and to a lesser extent the relative humidity, and the air velocity over the material surface, in particular for evaporation-controlled emissions. In addition, sorption properties of the chamber wall are important.

Recovery from the F L E C The recovery of two typical VOCs, dodecane and 2-ethylhexanol, has been determined to be about 100% (Wolkoff et al., 1995). They are a typical nonpolar and polar VOC, respectively, and their boiling points are 216°C and 183-186°C. Analytical sensitivity of emission testing by use of the F L E C Sorbent stability and cleanliness, e.g. background buildup, the chamber background, the sampling volume, the air exchange rate (dilution factor), the material loading (m2m-3), the GC column performance and linearity of the calibration curve of VOCs and the detector response of VOCs are determining the overall sensitivity of the emission test method. In addition, the column performance and the method of integration of the gas chromatographic raw data may also influence the result. Regarding the FLEC, it appears that the air exchange rate and the sorbent background

are the salient factors which control the overall sensitivity of the method. Applying a split between the thermal desorber (ATD 400, Perkin Elmer) and the GC analytical column of 1:5, the detection limit (3 × S.D. at the lowest concentration level) of e.g. toluene is 3 ng m - 3 for a sampling volume of 1.8 E and FLEC air supply of 300 ml m i n - 1. If it is assumed that the emission rate is the same in the FLEC and in the standard room (cf. Tablel and equation (1)), this would correspond to a Cm (standard room) concentration of 2 #g m - 3 compared with the toluene indoor relevant odor threshold of 3 mg m - 3 (50% of odor detection threshold, see Table 3). In the lack of a proper emission model for sealants, their t(Cm) values could be determined by long-term emission testing of VOCs having odor thresholds above 2-20/~gm -3. The overall sensitivity is about 3-10 times lower for floor and wall materials, respectively. It can be increased by lowering the FLEC air exchange rate or by the use of combined gas chromatography/mass spectrometry with selected ion monitoring. For further analytical procedures, see Wolkoff and Nielsen (1993a).

F L E C comparison with standard room and small chamber The FLEC volume is small, which results in high air exchange rates. However, due to the FLEC's design, realistic air velocities (Girman, 1993) in the range 0.01-0.1 m s - 1 are easily achievable, see Table A1. Table A 1 shows that the area specific ventilation rates (air supply t~s - ~ per m 2 of material surface) to be found in the Danish standard room (Nielsen et al., 1994), to be achieved in the FLEC and in a small climatic chamber for flooring materials are in the same order. It is possible by change of the FLEC air supply to obtain a range of realistic area specific ventilation rates, but not independent of the air exchange rate.