A Review of Volatile Organics Emission Data for

A Review of Volatile Organics Emission Data for Building Materials and Furnishings

by Y. An, J.S. Zhang and C.Y. Shaw

Irlternal report (Institute 1 ~ONALYSE

Internal Report No. IRC-IR-750

Date of issue: November 1997

CISTI/ICIST NRC/CNRC IP,C Ser Received on: 12-16-97 Internal repart.

This internal report, white not intended for general distribution, may be cited or referenced in other publications.

A Review of Volatile Organics Emission Data for Building Materials and Furnishings Y.An, J. S. Zhang and C.Y.Shaw

ABSTRACT Published emission data of volatile organic compounds (VOCs) from building materials and furnishings are reviewed. The building materials and furnishings reviewed include coating materials (i.e., wood stain, varnish, wax, and paint), installation materials (i.e., adhesive and caulking), wood products, vinyl coverings, linoleum, and carpets. These emission data are summarized in tables and analyzed systematically. The emission data of the same type materials from different laboratories are compared. The emission characteristics and emission range of individual materials are given.

IRCNRC CMEIAQ: Report 4.1 (08197)

1. INTRODUCTION Building materials have been recognized as one of the major sources of volatile organic compounds (VOCs) in indoor environments. Reliable emission data are needed for selecting building materials to control the VOC level indoors. In this report, published emission data were evaluated. Data included in this report are those obtained by using well documented testing methods and procedures under typical indoor environmental conditions. 2. METHODS OF EVALUATION AND REPORTING 2.1 Criteria Emission data obtained from laboratory emission cells (FLEC), small chambers, fullscale chambers, and test buildings were reviewed. The operating conditions of these test apparatus and facilities are shown in Table 2.1. Table 2.1 Range of Operating Conditions of the Test Apparatus and Facilities Chamber

FLEC Small Full-scale

Vdwne (m

Air change rate

0.00M)35 0.003 1 20 30

171 200 05-4 0.5 2

-

-

-1

-

-

Air velocity (cmls) 350-1400 0-250 0 - 100

Humidity (46) 40-60 40-60 40-60

Temperahwe

CC) -

20 25 20 25 20-25

The two criteria used to screen the published emission data are methods and procedures used to collect and prepare the samples and the adequacy of the documented test conditions and results. For new material samples, the required information includes the shipping and storage procedures, the shipment date, package and storage duration. For used material samples, a description of the usage history is required. For wet material samples, the specimen description includes substrate preparation, application method, specimen size (or loading factor), amount applied per unit surface area, and elapsed time before placed in the chamber. For dry materials, the information includes specimen size (or loading factor) and edge sealing method. 2.2 Presentation of data Data expressed in terms of both numbers and graphs are accepted and included in this report. Systematic names according to Chemical Abstracts (CA) are used for VOCs. The emission data in this report are expressed in the following units. Appropriate conversion was made when unit in the original literature was different. Concentration: Emission factor: Rate constant: Elapsed time:

mglm:; m mh; h‘ , h.

f

JRUNRC CMEIAQ: Report 4.1 (08197)

Testing periods used in previous works often differ from each other. In order to facilitate analysis and comparison of the emission data, the technique of interpolation or extrapolation was used to calculate the emission factors at t = 0,24 h (1 day), 168 h (7 day) and 720 h (30 day), when appropriate. Interpolations of the data using the models that were given in the original paper were made to fit the measured data (e.g., the fmt order decay model). Extrapolations of the data were made only when the extrapolated period is less than 113 of the measured period. Interpolated or extrapolated emission factors are denoted as E*, E@m, or E@7m.

Unless specifically noted, the time zero in this review is defined as the start of the dynamic chamber testing, i.e., when the chamber door is closed after the specimen is placed in the chamber and the chamber is operated at the testing air change rate. When the test procedure included the pre-conditioning, the preconditioning time period was identified as t. In this report, t, for "wet" materials is the time between the application and the start of the dynamic test (i.e., the time zero). For dry materials, t is the time between unpacking the sample and the start of the dynamic test. 2.3 Report of Results For each material, the following results are reported:

8

VOCs identified and their headspace concentrations (if available); A brief description of emission characteristics; Measured emission factors which are defined as the emission factors measured (or interpolatedlextrapolated based on the measured data) at 0.24.168, and 720h after time zero; Models used, their coefficients, and the time period t in which the models are valid, based on the experimental data; Effects of sample preparation and test conditions (e.g., air change rate and RH) on emissions, if investigated,

The results were grouped as follows: Grouu 1. "Wet" individual coatin~materials. Materials belong to this group include: wood stains, varnishes, paints, wax. These materials are applied "wet" on a substrate. Theii emission characteristics are therefore dependent on both the coating materials themselves and the substrate used. VOC emissions from the "wet" coating materials can generally be divided into two periods (e.g., Tichenor, 1987, Chang and Guo, 1992, Wies et al., 1996, and Zhang et al., 1996): (1) an initial period (drying period) in which the emission rate is high, but decreases quickly with time; (2) a later period (after the surface become dry or a thin film is formed) in which the emission rate is low and it decreases slowly with time. During the first period of the emission, the emission is primarily controlled by the interfacial evaporative mass transfer process, while in the second period by the VOC diffusion through the material (internal diffusion).

IRUNRC CMEIAQ: Report 4.1 (08197)

Group 2. 'Wet" individual installation materials. This group includes materials such as adhesives, caulk and sealant, and varieties of joint, patching and texturing compounds. These materials may have similar emission profiles as that of "wet" individual coating materials, but their time scales for the internal emission process are expected to be larger due to the relative "thicker layer" and slower drying process. Group 3. Drv individual materials. This group includes the majority of materials used to construct and furnish residential and commercial buildings, such as carpets, gypsum wallboards, particleboard, oriented strand board (OSB), vinyl flooring materials, ceiling tiles, fabrics, etc.. VOC emissions from these materials are generally characterized by nearly constant or very slowly decaying emission rates. Group 4: Material svstemslassemblies. In practice, different individual materials are usually used together to form material systemslassemblies such as: carpet I1 adhesive I1 concrete; paint N gypsum board 11vapor barrier; carpet I1 underpad I/ plywood I1 wood joists; wax I1 vinyl sheet 11adhesive I1 concrete; polyurethane floor vanish I/wood stain I1 hard wood 11plywood 11wood joists; etc.. 2.3 List of Nomenclature

C :, C,: EF: EFo: EFlst: EFznd: EF,:

Sample surface area (m2); VOC concentration (mg/m3) in chamber air; Maximum concentration in chamber during dynamic test (mg/m3); Initial VOC concentration at the material surface in mass transfer model (mg/m3); Nominal emission factor (mg/m2h) at time t; Nominal emission factor (mg/m2h) at time of starting chamber test; First phase emission factor in double-exponential model (mg/m2h); Second phase emission factor in doubleexponential model (mg/m2h); Nominal emission factor (mg/m2h),defined as the emission factor at t hour after start of the chamber testing as reported by the original author(s); Interpolated or extrapolated nominal emission factor (mg/m2h) at time t (t = 0, 24,168 or 720 hour); Initial emission factor (mg/m2h) in the diffusion model; Emission decay rate constant in the first-order decay model (h-'); Interfacial mass transfer coefficient (mh) in mass transfer model; First phase emission decay rate constant in doubleexponential model (h-I); Second phase emission decay rate constant in doubleexponential model (h-I); Adsorption rate constant in sink model (mh-I);

I R W C CMEIAQ: Report 4.1 (08197)

kd : kdif:

Ke:

ks:

L: M:

hlZ: N:

RH: t:

T: E: TVOC: U:

v:

Desorption rate constant in sink model (h"); Emission decay rate constant in the diffusion model (m-'K'); Adsorption/desorption coefficient in sink model (m), K = k$kd; Rate decay constant at the material surface in mass transfer model @"); Loading factor, i.e., sample area divided by chamber volume (m21m3); Sample mass (g); Mass per unit area in sink (mg/mZ); Air change per hour @'I); Relative humidity (%); Test time period (h); Temperature CC); Preconditioning time period (h); Total VOCs identifkl and measured by GUFID or GUMS; Air velocities (mls); Chamber volume (m3);

3. WET INDIVIDUAL COATING MATERIALS

Coating materials are essentially made of oils or resins which are dissolved in solvents. Most of the wet materials can be classified as solvent-based or water-based. The former indicates that organic compounds are used as solvent while the latter means that water is used as the primary solvent. VOC contents of these two types of wet materials are quite different. Solvent-based coatings normally contain 10% - 40% of VOCs (Ancona et al., 1993), while water-based coatings contain about 2% - 12% of VOCs (Jenkins et al., 1995). The VOCs initially emitted from solvent-based coatings are mainly those in the solvents. They are different from those initially emitted from water-based coatings. The emission profdes are also quite different between the two type of coating materials. Emissions of individual coating materials will be discussed in detaiIs as follows. 3.1 Wood Stains Major VOCs emitted from wood stains were identified to be nonane, decane, undecane, dodecane and 1,2,4-trimethylbenzene (Chang and Guo, 1992b, and Zhang et al., 1996). Other VOCs identified from headspace test are 2-butanone, benzene, hexane, trirnethylhexane, and cyclodecane (Tichenor and Guo, 1991). Most of these VOCs represent the composition of mineral spirits which are the common solvents, or thinners for wood stains. Zhang et al. (1996) reported that the TVOC equilibrium concentration measured in the headspace of a vial containing 2 ml wood stain sample was 10809 mg/m3. The measured equilibrium concentrations of nonane, decane, undecane, and dodecane were 2074, 1172, 21 1, and 12 mg/m3, respectively. These equilibrium concentrations correlate to the volatility of the corresponding compounds. That is, the measured concentration of a compound is directly propotional to its vapor pressure but inversely proportional to its boiling point (the vapor

I R m C CMEIAQ: Report 4.1 (08197)

pressures of nonane, decane, undecane, and dodecane, at 2 3 ' ~and 1 atrn, are 4.6, 1.70, 0.66, and 0.27 mmHg, respectively). Chang and Guo (1992b) proposed a double-exponential model for predicting the wood stain emission characteristics. This model suggested that the emission process consists of two phases, i.e., f m t phase emission and second phase emission. Data in Table 3.1 indicated that the emission factor and rate decay constant in the first phase emission increase with the vapor pressure of the corresponding compound. The first phase emission was thus postulated as an evaporation-contr011ed process. The rate decay constants in the second phase emission are much smaller than those in the first phase emission, and are close to those of dry materials (see chapter 5). The authors suggested that the rate decay constants in the second phase emission are related to diffusivity of the corresponding compound. The second phase emission was thus interpreted as a diffusion-controlled process. Furthermore, the data shown in Table 3.1 were measured at different test conditions, i.e., air change rates were from 0.36 - 4.7 ACH and 3 loading factors were from 0.1 - 1.3 m211x1 . In general, the emission factor and rate decay constant in evaporation process increase with air change rate, but no clear correlation was found for the second phase emission data and air change rate. Table 3.1 Emission data estimated by a double-exponential model VOC

V.P.

(nrmHe.) Nonane 1.2.4-Trimethylbenzene Decane Undecane

4.6 2.23 1.7 0.66

EFI, (dm%) 220-6643 96-2816 242-6673 51-1103

kw 4

EFw

0.59-10.0 0.34-6.22 0.22-4.16 0.101.57

0.19-2.11 0.17-1.24 0.71-6.03 0.52-6.65

t

Kz.I.d 0.007-0.036 0.0060.028 0.005-0.029 0.005-0.035

t

@)

(h)

cO.1 < 0.1 280

0.07

Note:

22 28 56 22 28 56

0.043 0.048 0.605 0.525 0.736 1.97

24 24 24 24 24 24

0.018 0.020 0.009 0.015 0.016 0.005

336 336 336 336 336 336

Data are from Clausen, 1993 b first-order decay model: EF = EFo ex$-kt). Chamber parameters: 0.234 m2,23'~, 45% RH, 0.25 ACH,M.36 m /m3; Specimen preparation: The paint was applied on tin plated steel sheets (250mm x 341mm)with paint roller.

Wikes et al(1996) developed a doubleexponential model to study the emission of latex paint applied on gypsum boards. The emission of the individual VOCs (12-propanediol, ethylene glycol, 2-(2-butoxyethoxy)ethanol, and texanol) was in general characterized by two components, fast emission and slow (diffusion-controlled) emission. It was found that the emission factor and rate decay constant in the fast emission stage were much higher (i.e., over 10 times) than those in the slow emission stage. However, during the fast emission stage which is corresponding the early emission period, only 10% or less of the total VOC mass was emitted. The emission factors and emission decay constants estimated by the doubleexponential model are shown in Table 3.13. The EFI, and kl, represent the emission factor and decay rate constant in the fast emission stage and the EF- and km represent the emission factor and decay rate constant in the slow emission stage. A comparison between the emission data and the physicochemical data of the compounds in Table 3.13 suggests that the fast emission stage and the slow emission stage are related to the evaporation process and the film diffusion process, respectively. Furthermore, a comparison between the km values in Table 3.13 and the k w values in Table 3.1 (wood stain emission estimated by the double-exponential model) suggests that the rate decay constants of individual VOCs in the diffusion process are in the same range for both paint and wood stain. Table 3.13 Emission data of paint estimated by a doubleexponential model VOC 1.2-Propanediol Ethylene glycol 2-(2butoxyethoxy)ethanol Texanol

V.P. ( d g )

0.2 0.05 0.02 0.0019

mw. Wwl) 76.1 62.1 162 216

EFl,

0.82 2.81 0.25 1.46

EFa

k~

km -1

(m)

49.7 1.34 0.16 0.94

0.0058 0.003 0.055 0.0026 0.022 0.0099 0.22 0.013

(4)

-1

t

01) 240 240 240 240

Note: Data are from Wilkes et al., 1996; Specimen: Paint sample was applied on gypsum board and immediately inserted into the chamber; Doubleexponential model: EF = EFI, exp(-kid + EF- e x N - k ~ ) .

The existing emission data for paints are summarized in Table 3.14. Variations in the test results are probably due to differences in the test methods, procedures and environmental conditions.


Table 3.14 Paint emission data 1

I

Wa

VOCs

-Paint Solvent-fReLat€x Paim AcrylareIatexPaint WataiaXmPaint WarabcmePaint waterbcmepaid WataiaXmPaint warabcme~aim Warabcmem WaretrmeAPylic WarabcmeAcrytic

lVOC TVOC TVOC TVOC

WamtmceAnylic WaterbcmeAuyk W - F Warabcmem

WhiteSpirit 1~~ 2-Bidoqe&ad uodecane 1.2-Propaoediol Blrtand

Tegml Texand Texand

TVOC TVOC

k (h3 1.86 0.04 0.01030 8473.7 0269.1 0.868.1 0112833 0.401.0 OM136 MOl4 0.024.16 0.04 0.22 0.18 0.29

O.iBMit57 0.014QOR a012m QWiO.089 am0.10

t.

t Q)

48 48 48 24 24 24 24

da

01)

da da Sn 672 ~4 6n

24

m

672

da da

6R 6R

18.7 1.48 23.5 5.3 0.07

a$

672

da

6n

IJa

672 672 24

da da

24

w

3% 3%

% (nghlP1)

12Js

1 1 1 0.16 2 0.0015 2 2 2.34 2 0.0056 6.9~10-~ 2 3a 3a 3a 3b k

M 3e 0.9 2.2

4a

4b

Note: All EF, and Eat values are estimated by the first-order decay model: EF (or EQ) = EFo exp(-kt). Ref. 1. Tlddioceu et al. 1993; Subarate: Gypsum M , Chamber parameters: lm3. 23% 45%, 0.5ACH and L=0.41mz/m3; 2. Clausen etal., 1991; Subsltate: T i - p w & sheet; Chamber parameters: 0.234m3, 23Oc, 45%, 0.25ACH and ~=1.46m~/m~; 3. Gumarsen ad,1994; Substrate: Aluminum p*, Chamber parameten: a: 0.051m3, 22'~. 50%. SdlACH, U=O.I5m/s, L=3.1m21m3; b: 3.5~10-*m3. 22'~. 50%. 171ACH. U=O.O035mls: c: 28.5m3, 22%. s&, ZACH, u=o.imls; d: 1m3(glass), 22'~. 50%. 3ACH. U=0.13ds; e: 0.003m3, 22%, 50%; 4. Tikkonen et al., 19%. Substrate: Gypsum board; Chamber parameters: a: 0.062m3 (glass), lACH, 23'~. 45%; b: 0.12m3, 23'~. 45%. O.5ACH.

In an effort to reduce the variation in the emission test results and to develop a standard test method for paint, a comprehensive interlaboratory comparison study on the small chamber testing of latex paints has been conducted among 18 partners (De Bortoli et al., 1995). The chamber conditions were T = 23'~, N = 1, RH = 45%. L = 0.5 m2Im3,and U = 10 c d s . The paint samples were applied on either a stainless steel plate or an aluminum plate. The average paint film thickness was about 66 pm. The test period was 312 hours. The measured concentration ranges for 2-(2-butoxyethoxy)ethanol were between 0.065 and 3.395 mg/m3, 0 and 0.415 mg/m3, and 0 and 0.05 mg/m3, at 3h, 78h and 240h, respectively. The results indicate that a large discrepancy, among these laboratory measurements still existed, even though it was

IRC/NRC CMEIAQ: Report 4.1 (08197)

much better than the previous interlaboratory comparison results (Colombo et al, 1993). The discrepancy was attributed to the factors, such as specimen preparation, chamber sink effects, surface air velocities, and chemical analysis methods. In summary, tbe VOC emission from paints have been studied in detail. Substrates, specimen thickness, and chamber conditions, such as air flow rate, air speed, temperature and humidity, are the main factors affecting the emissions of wet paint samples. The TVOC initial emission factors of solvent-based paints are in the order of id mg/m2h, which are lower than those of other coating materials. The TVOC initial emission factors of waterborne paints ranged from 9 to 75 mg/m2h. The rate decay constants for solvent-base wet paints are in the order of 10.' - 10' h-', while for waterborne wet paint are in the order of lo-*- lo-' h-'. In general, the emission factors for fully dried paints (i.e., 48 hours after the application) are below 0.1 m g l d h with the rate decay constant of less than 10'' h-'. 3.5 Summary of coating material emissions A comparison of the VOC emissions from individual coating materials indicates that two processes generally exist, i.e., drying (evaporation controlled) process and post-drying (diffusion controlled) process. The emission in the drying process, which usually takes about a few hours, varies greatly with the test conditions. The rate decay constants for this emission are generally higher than lo-' h". The emission in the post-drying process can be characterized by relatively lower emission factors (< 10 mg/m2h) and rate decay constants (S h"). 4. INSTALLATION MATERIALS Installation materials include adhesives, caulks and sealants, joint patching and texturing compounds, and grout or mortar. The emission data of these wet installation materials were summarized in Appendix 2. Those emission data measured during installation process, e.g., emission of seamed carpet will be discussed in the section of material systems. 4. I Adhesives Adhesives, like paints and other wet materials, are either solvent based or water based. Solvent-based adhesives contain synthetic resins, and xylene, toluene, 1,l.ltrichloroethane, acetone, or other solvents. Water-based, latex adhesives contain smaller quantities of organic solvents, so they are also called "low-VOC' adhesives. It has been reported (Person et al., 1990) that the VOCs emitted from both solvent-based and water-based adhesives include aliphtic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons, esters, alcohols, ketones and aldehydes. While aliphatic and aromatic hydrocarbons are major VOCs, i.e., from 35% to 70%. in solvent-based adhesives, alcohols (mostly diols) represent 20 - 50% of TVOC in water-based adhesives. Aliphatic and aromatic hydrocarbons have been also reported to be the major VOCs in water-based adhesives when no alcohols are identified (Tichenor and Mason, 1988). The available emission data of adhesives are listed in Table 4.1.

I R W C CMEIAQ: Report 4.1 (08197)

Tichenor and Mason (1988) reported that the adhesive TVOC emission factors (mg/m2h) of one adhesive sample at 0.5h, lh, and 5h were 1700, 700, and 100, respectively. The test was conducted in a small chamber at 1.84 ACH and 50% RH.The data indicated that the emission factors decrease about 95% within the first 5 hours. A long term study (Black et al., 1991) showed that the TVOC emission factor of a solvent-based latex adhesive decreased about 90% during the fmt day of the test, while it required 16 days to decrease about 99%.The EFo, EF24, E F I ~and ~ . EF7rn of this latex adhesive are shown in Table 4.1. The emission factors of water-based adhesives were much smaller than that of solvent-based adhesives. It was reported (Davidson et al., 1991) that the emission factor of a water-based adhesive decreased 99% within 6 days (seeTable 4.1). Emission profiles of individual VOCs from adhesives are rarely studied. The only individual VOC, which was measured is toluene (Nagda et al., 1993). Unfortunately the reported emission rate is in mgh with no reported loading factor and application area. The data are, thus, not included in this review. The emission rate of toluene, as reported decreased 99% within the first 10 hours of the test. This result is apparently comparable to previous TVOC emission data reported by Tichenor and Mason (1988). Table 4.1 Emission Data of Adhesives

Note: All EF,values are estimated by the fust-order decay model: EF = EFo exN-kt).

Ref. 1. Black et al., 1991; Chamber parameters: 0.05m3,2 5 ' ~ .IACH, 50%RH, and M.41; 2. Davidson et al.. 1991: Chamber parameters: same as above.

4.2 Caulks and sealants

Caulks and sealants are used to fill gaps or create seals where some flexibility is required. The difference between sealants and caulks is that sealants are load-bearing, elastic joint materials capable of expanding and contracting with the motion of joints, whereas caulks are not load-bearing materials (Maslow, 1982). Traditional caulking materials were linseed oil putties, tree resins, and asphalt. Modem caulkings for construction are made primarily from synthetic polymers, some of which are from the same chemical families as paints - latex, acrylics, and urethanes. Others, such as those made from silicones, polychloroprenes, polysulfides, and butyls, are quite different from paint bases. The most common caulkings for indoor use are made from acrylic latex and silicones. The solvent-based caulkings are formulated with hazardous solvents, such as acetone, 2-butanone, toluene, xylenes, and


alcohols. The so called low-toxicity caulkings are also made of synthetic resins, but contain little or no hazardous solvents or fungicides. The major VOCs identified from caulking materials are mostly representative of the solvent components. For instance, the reported major VOCs identifed by GClMS in a silicone caulk were 2-butanone, butylpropionate, 2-butoxyethanol, butanol, benzene, and toluene (Tichenor and Mason. 1988). in an oil-based acrylic sealant were acetone, hexane, methylcyclopentane, cyclohexane, dimethyloctanols and BHT (Wolkoff et al., 1996a), and in a waterborne acrylic sealant were butanol, 2-(2-butoxyethoxy)ethanol, and 2-(2butoxyethoxy)ethanol acetate (Wolkoff and Nielsen, 1996). The published emission data of sealants and caulks are listed in Appendix 2b. Their emission values are shown in Table 4.2. Analysis of these data indicated that the caulking emissions are strongly dependent on the type of caulkings and the air change rate in the test chamber. Different type of caulkings may present very different emission factors. For instance, the initial emission factor of TVOC measured from a silicone caulk was 476 mg/mzh and the major VOCs were 2-butanone, 2ethyIhexano1, and butylpropionate (Durn, 1987). The measured initial emission factor of a seam sealant was 2.96 mg/m2h and the major VOCs were toluene, 1,3-dioxalane, 2-butanol, l,l,l-trichlomthane, and tetrachloroethylene, (Davidson et al., 1991). Both experiments were conducted in small chambers with volume of 0.166 and 0.050 m3, respectively, and the air change rates of 1.84 h-I and 1.0 h-', respectively. This difference would be resulted from the different VOC contents in the two samples. Catananti et al. (1993) and Levin (1992) reported that the emission factor of silicone caulk was about 3 - 7 times higher than that of latex caulk. The high emission of silicone caulk is probably due to the high solvent requirement for its manufacturing. It is noted that the emission factors may be quite different even if the caulkings are the same w.As an example, the initial emission factors of 2-butanone, butylpropionate, and 2-ethylhexanol in one silicone caulk were approximately 75, 40, and 28 mg/m2h, respectively (Tichenor and Mason, 1988), whereas in another silicone caulk were approximately 416, 137, and 213 mg/m2h, respectively (Dunn, 1987). The two silicone caulks were measured in different laboratories and probably produced by different manufacturers. The results suggested that caution should be exercised when emission factors are used to characterize the individual materials. In general, water-based caulkings had relatively lower emission rates than silicone-based caulkings (see Table 4.2). Effect of air change rate on caulking emissions have been investigated by a number of groups, with no consistent conclusions. Some researchers (Tichenor and Mason, 1988, and Wolkoff et al., 1993b) reported that the emission factors increased with the air change rate while other (Durn, 1987) reported the opposite (i.e., the emission factors increased as the air change rate decreased, as shown in Table 4.2). It is noted that most emission factors presented in Table 4.2 are derived from diffusion models, so they are shown as Fo. A comparison between the Fo values and the EFo values derived from the first-order decay model indicates that there are no noticeable deviations between these two emission factors, as shown in Table 4.2. The


experimental data which showed that the emission factors increased with the air change rate, were measured using a procedure which involved one week drying period before starting the chamber test. On the other hand, the experimental data which indicated the emission factors increased as the air change rate decreased, were measured using a procedure which included no drying period. Further experiments are needed to confvm the relationship between the sample preconditions and the effect of air change rate on caulking emissions. The emission factor values changed about 10% to 100% when air change rate changed about 4 - 5 times (see Table 4.2).

Gunnarsen et al. (1994) tested the emission of a silicone sealant in 6 different chambers. These chambers included a FLEC (3.5x10-' m3), two stainless steel chambers (0.051 m3), two glass chambers (0.003 m3 and 1 m3), and a full-scale chamber (28.5 m3). The sealant samples had been preconditioned in the chambers for six days before starting the measurements. The results varied significantly (e.g., the emission factors of 3,7-dimethyloctanol changed fkom 1.1 mg/mzh to 7.2 mg/mzh). Table 4.2 Emission Data of Caulks and Sealants

3,7-Dimethylocranol 3,7-Dimethylocranol SiliconeBased Acrylic Caulk Waterborne Acrylic Sealant

Ref:

Hexane 2-Ethylhexanol Dimethyloctanol Butanol 2-(2-Butoxyethoxy) ethanol 2-(2-Butoxyethoxy) ethanol acetate

13.7 18.4

14.3 18.9

O.MXX)9

0.00013

168 168

168 168

12.9 0.51 5.92 6.% 100.5

0.0006 0.027 0.00014 0.00066 0.00001

24 24 24 24 24

5000 5000 5000 5000 5000

3

28.4

0.00008

24

5000

3

13.4 175

11.9 13.1

1. Davidson et al.. 1991; Test conditions: 0.05m3 stainless steel chamber, 25'~. 1 ACH, 50% RH,M . 4 1 ; Major VOCs: Toluene, 1.3-dioxalane, 2-butanol, l.l,l-trichloroethane, and tetrachloroethylene; EQ,values are estimated by the fust-order decay model: EQ = EF,, exp(-kt). 2. Wolkoff et al., 1993b; Test conditions: 3.5x10-~m~ FLEC, 22'~. 50% RH, L20.6; a) 171 ACH; b) 343 ACH; C)684 ACH,

2b 2c

3 3 3 3


EQt values are estimated by the diffusion model: EF (or EQ) = l/[kmtt + Fa]; 3. Wolkoff and Nielsen, 1996b; Test conditions: 3.5x10"m3FLEC, 23°~,51%RH,514 ACH,L20.6. E@,values are estimated by the diffusion model: EF (or E@)= 1/[ k& + Fa].

As shown in Table 4.2, the emissions of caulks and sealants are characterized by a long enduring period, as illustrated by the high values of EF168. It is noted that some of the tested sealant samples had been dried for one week before starting the measurement (Wolkoff et al, 1993b). In a real life, this slow emission can take months to disappear (Leclair and Rousseau, 1993). %chenor and Mason have noticed that the emission enduring time is different from compound to compound. 2-Ethylhexanol endured much longer than 2-butanone and butylpropionate. This may be understood by the fact that 2ethylhexanol (B.P.184'~) is less volatile than 2-butanone (B.P. 80'~) and butylpropionate (B.P. 145'~). The less volatile compounds are likely reluctant to be released from the surface. In addition, the hydroxyl groups in alcohols may have special attraction towards the silicones (siloxane polymers). Nonetheless, hexane, a high volatile compound (B.P.6g0c), displayed slow emission as well, indicating that a more complicated interaction may be involved in the material surface or within the material. To summarize, caulkings, in particular, silicone-based sealants and caulks, have been tested in small chambers for their short term emissions. The emission data indicated that the initial emissions (no preconditioning) of caulkings are very high. As shown in Table 4.2, EFo of TVOC was over 1000 mg/m2h. The VOC emission factors after drying for one week are much lower than those without drying. Approximately over 90% of VOCs were emitted during the one week drying process. The remaining VOCs (less than 10%) underwent a slow emission. The time period of this slow emission depends on the individual compound. There is apparently a lack of long term emission data (i.e., over a month or longer period of time). 5. DRY INDIVIDUAL MATERIALS Dry materials are those used as interior construction panels, flooring, wall covering, and carpeting, and furniture (e.g., office work station, kitchen cabinets). The individual materials are wood board, gypsum board, linoleum, carpet, and vinyl coverings (including flooring and wall covering). Other dry materials such as concrete, ceramic covering, marble, and stoneware are not included, since there have been no emission data available for these materials so far. VOC emissions from dry materials are generally characterized by nearly constant or very slow emission decay rate. 5.1 Wood boards

Wood boards include plywood, oriented strand board (OSB), particleboard, and fiberboard. The major VOCs emitted from these wood boards are formaldehyde and terpenes. It has been reported that the percentage of aldehyde and terpenes in total emissions of wood boards ranged from 25% to 100% (Sundin et al., 1992). To prevent formaldehyde emission, woodboards are usually sealed with oil-based coatings or with specially formulated sealers. The


emissions of these oiled woodboards are, therefore, characterized by the VOCs commonly observed from wood coatings. Published emission data of wood boards are listed in detail in Table 5.1. Difference in manufacturing, duration of shipping and storing, sample preparation, and testing conditions, etc., may account for the variations. Van der Wal(1990) measured the emissions of four different plywood boards in a small chamber. The emission factors of formaldehyde measured at 1 hour after the test ranged from 0.015 to 1.06 mg/m2h and those measured at 24 hour ranged from 0.005 to 0.72 mg/m2h. The measured emission factors for terpenes also varied in a wide range, i.e., from 0.3 to 2.4 mg/m2h at 1 hour and from 0.08 to 0.85 mg&h at 24 hour. Since the sample preparation and test wnditions were all the same for the four plywood samples, the variation in formaldehyde (or terpenes) emission is probably due to the different manufacturing process and different storage duration. The TVOC emission factor of plywood was about the same as that of formaldehyde and terpenes, 0.044 mg/m2h (Molhave, 1982, see Table 5.1). However, the emission factor of a factory-coated plywood sheet was 0.48 mg/m2h (Colombo et al., 1990), indicating that some VOCs were originated from the coatings. Saarela and Sandell (1991) found that the TVOC emission factors of several pinewood and birchwood manufactured differently were very similar, i.e., 0.15 - 0.68 mg/m2h(Table 5.1). In addition, the age of these wood boards apparently had no impact on the emissions. A long term emission of a factory-coated parquet was investigated by Tahtinen et al (1996). The emission factors for this parquet were 0.1 1,0.09,0.07 mg/mZhwhen measured on the 3rd, 14th, and 28th days, respectively, after starting the test. The test was conducted in a 0.12-m3 stainless steel chamber with 23O~,45%IW, 5096, and L = 0.4 m2Im3. The result indicated a slow emission decay after start of the test. Longer term test may be needed to trace this emission decay. The TVOC emissions of particleboards were reported to be 0.12 - 0.95 mg/m2h (Molhave, 1982 and Black et al., 1991). Slow emission decay was also observed for particleboard emissions. The TVOC emission factor of fiberboard, as shown in Table 5.1, was about the same as that of particleboard (0.12). This is understandable since both particleboard and fiberboard are made from wood dust and chips and pressed into sheets using glues. Different VOC emissions are most likely resulted from different amount of glue used during the manufacturing process. The emission factor decreased about 12% during a six-day test, i.e., from 0.95 mg/m2h to 0.84 mg/m2h, as shown in Table 5.1 (Black et al., 1991). Gypsum boards which are made of gypsum and fibers contain barely organics, despite some chemicals may be added to make it water-proof or for other purposes. Hence, gypsum boards are characterized by their very low emissions, i.e., 0.003 - 0.064 mg/m2h (Table 5.1). The g sum board which was glued with paper on both sides had emission factor of 0.14 mg/mP' h, higher than that without glued paper.


Table 5.1 Emission factors for wood boards

U n d Pinewood O.lYear, Cmted B i i w m d 0.1Ye.x. Cmted PicePinewood 1 YercrLxquaed Pinewmd Haniwmd Particleboard Particleboard Particleboard, 14 days Particleboard 10 years Fiberboard Gypsum Board Gypsum Board Gypsum Board with Glue Paper

TVOC TVOC TVOC TVOC TVOC TVOC

TVOC TVOC TVOC TVOC

0264 0.03 0.13 0.15 0.04 0.12 0.W3 0.026-0.064 0.14

216 168 24 24 168 168 24 240 24 48

da da 144 da da da n/a da nla da

0.952

0.837

5 4 6 2 4 4

2 3 2 7

Note: All EF,values are estimated by the ht-order decay model: EF = EFo expf-kt). Ref: 1. Van der Wal, 1990: Chamber conditions: 15m3, 23'~. 50%RH, 1 ACH, Ll m21m3. 2. Molhave, 1982; Chamber conditions: lm3, 21°c. 40%RH, 1ACH, L= 0.73 m2/m3(average). 3. Colombo et al., 1990; Chamber wnditions: 0.45m3, 23OC. 45%RH, 0.25 ACH, LA.2 m2/m3. 4. Sundin et al., 1992; Chamber conditions: 1 m3, 23'~. 50%RH, 14 ACH, M . 2 m2/m3. 5. Saarela and Sandell, 1991; Chamber conditions: lm3, 23'~. 45%RH, 0 5 ACH, I=O.41 m2/m3. 6. Black etal., 1991; Chamber conditions: 0.05m3, 2 5 ' ~ . IACH, 50%RH, and k0.41m2/m3. 7. Tirkkonen et al., 1993; Chamber conditions: lm3, 23'~, OSACH, 45%RH, and L4.41m2/m3.

In summary, wood boards and gypsum boards have low TVOC emission factors (usually below 1 mg/m2h) relative to "wet" materials, although different manufacturing and material treating (e.g., lacquered) processes give rise to a broad range of emission factors. In general, emissions of wood boards are about one order of magnitude higher than that of gypsum boards. Moreover, emissions of wood boards displayed a slow decay emission rate. The duration of the longest test reported so far is about one month. Long term tests (i.e., longer than one month) are needed to characterize this emission decay.

5.2 Vinyl coverings


The vinyl radical is designated chemically as CH2--CH-. The term vinyl resins (or vinyls) could be applied to substitute ethylenes and their many copolymers such as polyethylene, polystyrene, polyvinyl chloride (PVC), polyvinyl acetate, acrylic ester, methacrylic ester, and even some of the synthetic rubbers (e.g., isoprene). Vinyl resins are mainly copolymers rather than homopolymers. Homopolymers are polymers in which the monomericunits are all identical. Copolymers are polymers in which the monomeric units are different (Maslow, 1982). Typical exampIes are polyvinyl chloride-polyvinyl acetate resins, polyvinyl chloride-acrylonitde resins, and polystyrene-butadiene resins. Commercial vinyl resins may also contain a small percentage of a modifying resin, such as an acid or an acid anhydride, which is distributed randomly in the polymeric chains. Vinyl coverings including flooring and wall covering, are mainly made of these vinyl resins. For commercial purposes, a number of additives such as plasticizer, viscosity modifier, stabilizer, pigments, fillers, and frothing agents, are added to vinyl coverings. These explain their complex compositions. The VOCs emitted from vinyl coverings are mainly originated from these additives and the residual solvents used during manufacturing. The VOCs detected from seven PVC floorings produced by different manufacturers were those of aliphatic and aromatic hydrocarbons, akylphenols, alcohols, aldehydes, ketones, aliphatic and aromatic esters, and carboxylic acids (Bremer et al., 1993). Chlorinated hydrocarbons were also detected from vinyl floorings and wall coverings (De Bortoli et al., 1993 and van der Wal, 1990). indicating that PVC was one of the major monomers in these vinyl coverings. These VOCs are mainly originated from manufacturing additives. For instance, the major VOCs detected from a number of plasticizers are aromatic esters. The major VOCs detected from viscosity modifiers are aliphatic and aromatic hydrocarbons, some ketones, and alcohols (SaareIa et d.,1989). Trimethylpetandeioisobutyrate (TXIB) which is one of SBS compounds (Rosell, 1990) is frequently detected from vinyl coverings (Kirchner et al., 1993). Moreover, toluene, phenol, and phenolic compounds have been found as major components in vinyl stabilizers (Saarela et al., 1989) and 2,24,6,dpentarnethyIheptane has detected solely from a fluidizer (De Bortoli et al., 1993). Emissions of vinyl coverings are complicated by their complex compositions. The TVOC emission factors of vinyl coverings measured by the same pnnxdure were found to vary from 0.1 to 2.3 mg/mzh (Molhave, 1982), or from 0.3 to 10 m&h (Black et al., 1993). It has been pointed out that the wide range of emission results (0.03 - 1.4 mg/&h) from vinyl coverings is the result of the different manufacturing processes, specifically different ingredients of additives (Gustafsson and Jonsson, 1993). The emission factors of various vinyl coverings are summarized in Table 5.2. The TVOC emissions of vinyl coverings (De Brotoli et al., 1993) showed a little fast emission rate decay in the beginning (e.g., declined 73% within 24 hours) and followed by a very slow decay (e.g., declined 22% from 24 hour to144 hour). For PVC samples which had been conditioned in the chamber for 24 hours, the emission decay in the f m t 24 hours was slower, e.g., 19% (Tahtinen et al, 1996). Long term test indicated that the emission factors of


vinyl coverings were almost unchanged after 7 days (Tahtinen et al, 1996). As shown in Table 5.2, the initial emission factors of 0.5 year-old and 1 year-old vinyl coverings are in the same order of magnitude (i.e., 2.19 and 1.63 mg/m2h, respectively). However, a vinyl covering which had been used for 2-3 years had lower emission (0.27 mg/m2h) than those never used (Saarela and Sandell, 1991). These results suggest that the VOC emissions from vinyl coverings have a very slow decay rate. The results of an international comparison experiment involving 20 laboratories on the determination of VOCs emitted from the same type of PVC tiles showed that the mean TVOC emission factors at 48h and 72h were 1.96 mg/m2h and 1.66 mg/m2h, respectively (Colombo et al., 1993). The relative standard deviations were 34% and 42% for 48h and 72h. respectively. The mean emission factors at 48h for phenol, 1,2,4-trimethylbanzene, decaue, and undecane were 0.79, 0.70, 0.16, and 0.15 mg/m2h, respectively, while at 72h were 0.68, 0.61, 0.14, and 0.12 mg/m2h, respectively. The relative standard deviations for these results were between 26% to 40%. These emission data indicated that the emission rates decreased 15% - 20% from 48h to 72h. It was noted that tests in larger chambers produced less scattered results than tests in smaller chambers. This was due to the heterogeneity of the material, since a smaller size of test specimen had to be used in small chambers to keep the same loading factors as in large chambers. Tests of specimens with different sizes indicated that the relative standard deviations were from 11% to 23% when the same chamber and test procedure were used. Wolkoff et al. (1996b) studied the effects of air velocity, temperature, and relative humidity on the emissions of 2-ethylhexanol and phenol from PVC coverings. The emission factors of both compounds increased as the air velocity rose from 10 cmls to 30 cmls and also sipnificantly increased when temperature rose from 2 3 ' ~to 6 0 ' ~ .However, no change was observed when temperature rose from 2 3 ' ~to 35'~. Moreover, the emission factors of the two compounds significantly increased under anaerobic conditions. Clausen et al, (1993) evaluated emission data of vinyl coverings tested in three different chambers, including two stainless steel chambers and an FLEC,with a hrst-order decay model and found that the fmt-order model was not sufficient to describe the emissions of cyclohexanone and phenol, which were in fact controlled by internal diffusions. The initial emission factors estimated by a diffusion model were in the same range as that estimated by the first-order decay model (i.e., 0.3 - 2.8 mg/m2h and 0.04 - 0.15 mg/m2h for cyclohexanone and phenol, respectively), while the emission decay rate estimated by the diffusion model which were close to the experimental results were higher than that estimated by the fust-order decay model. Bremer et al (1993) applied the double-exponential model (one exponential for fast decay emission and the other for slow decay emission) to describe the VOC emission from PVC-floorings. The results obtained by fitting the TVOC emission of three different PVC samples indicated that the rate decay constant for the fast decay emission was about 0.1 h-', while the rate decay constant for the slow decay emission was below 0.013 h-'. Table 5.2 Emission factors for vinyl coverings


wc wall c

n

EogtishWC1ye;a.d FionishWClyear,unused F d WC 0 5 year, unwed Fionish WC 2-3 year, used W C c3shion Vinyl Floaing

Vinyl Wall Coverings

~

TVOC TVOC TVOC TVOC TVOC Cyclohexanone cyclohexanone Cyclohexanone cyclohexanone Cyclohexanone Cyclohexanone Cyclohexanone Phenol Phenol Wen01 Phenol Phenol Phenol Phenol 2-Ethylhexan01 Formaldehyde Toluene Ethylbenzene Xylenes Ethyltoluenes Alkanes Formaldehyde Toluene

1.12 1.63 2.19 0.27 0.43 064-150 1.36 0.97 0.45 0.31 2.77 1.82 OI]M(KTIl 0.14 0.11 0.057 0.048 0.14 0.13 0.07 0.09 0.62 3.0 2.9 0.010

216 216 216 216 24 da

o 0 o

0 0 0 nla 0 0 0 0 0 0 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2

nla nla nla nla da

0.35

600

240 240 240 240 240 240 600 240 240 240 240 240 240 24

24 24 24 24 24 24 24 24

0.23

4 4 4 4 5 6 7a(i) 7a(ii) 7Mi) 7b(ii) 7c(i) 7c(i) 6 7a(i)

0.14 0.03 o.06a07 0.04 0.24 1.2 1.5 0.015 QmSLX5

Note: All EF, values are estimated by the first-order decay model: EF = EFo expi-kt). ReE 1. De Bortoli et al., 1993; Chamber conditions: 0.28m3,23'~. 45%RH, OSACH, L=lm2/m3. 2. Tirkkonen et al.. 1993; Chamber conditions: lm3. 23'~. 45%RH, OSACH, L= 0.41m2/m3. 3. Molhave. 1982; Chamber conditions: lm3,21'~. 40%RH, 1 ACH, L= 0.73 m2/m3(average). 4. Saarela and Sandell, 1991; Chamber conditions: lm3, 23'~. 45%RH, 0.5 ACH, M.41m2/m3. 5. Tahtinen et a& 1996; Chamber conditions: 0.12 m3, 23'C, 45%RH, O.SACH, M . 4 m2/m3. 6. Wolkoff et al.. 1991;

7a(ii) 7b(i) 7Wi) 7c(i) 7c(ii) 8 8 8 8 8 8 8 8 8


Chamber conditions: 0.234m3, 23'~.45%RH,0.25ACH. ~ . 4 1 m ~ / r n ~ . 7. Clausen et al., 1993; a: Chamber conditions: 3 . 5 ~ 1 0m3, . ~ 23'~, 5O%RH, 169.5ACH. L=505m2/m3; (i) Result of the fitting of the diffusion model; (ii) Result of the fitting of the first-order model; b: Chamber conditions: 0.234 m3,23'~. 45%RH, 0.12ACH. L4.45m2/m3; (i) Result of the fitting of the diffusion model; (u) Result of the fitting of the first-order model; c: Chamber conditions: 0.234m3,23'~. 45%RH, 0.2SACH. ~ . 4 5 m ~ l r n ~ ; (i) Result of the fitting of the diffusion model; (u) Result of the fitting of the first-order model; 8. van &I wal,1990. Chamber conditions: 15m3,23'~,50%RH, 1 ACH, L=1 m2/m3.

In summary, the initial emission factors of vinyl coverings ranged from lo-' to id mg/m2h for TVOC and lo9 to 10' mg/m2h for individual compounds, depending on the compositions of additives used in manufacturing. On average, emission of vinyl coverings is higher than that of wood boards. 5.3 Linoleum Linoleum is a traditional material processed with natural, renewable ingredients (linseed oil, cork, wood dust, and dyes), that have been heat-cured. It has been made by the same method for several generations (Leclair and Rousseau, 1993). The major VOCs emitted from linoleum were found to be aldehydes and the corresponding alkanoic acid such as hexanal and hexanoic acid These compounds represent the chemistry of linseed oil (Jensen et al., 1993). Other identified VOCs are alkanes, terpenes, glycol ethers, and aromatics (Kirchner et al., 1993 and Wolkoffet al., 1993a and 1995). Molhave (1982) reported that the initial TVOC emission factor of linoleum was 0.22 mg/dh. The emission factor of propionic acid, the major VOC emitted from linoleum ranged from 0.05 to 0.5 mg/m2h (Gunnarsen et al., 1994). The initial emission factors of other major VOCs from linoleum (e.g., hexanal and nonanal) are reported below 0.01 mg/m2h. These results indicated that the TVOC initial emission factor of linoleum is in general about same as that of wood products but lower than that of vinyl products (Table 5.2). The existing emission data for linoleum are listed in Table 5.3. Table 5.3 Emission Factors for Linoleum VOC

TVOC Propionic Acid

EFo (mg/mzh) 0.22 0.25 0.054 0.072 0.47 0.36

k -1) 0.0059

(h)

T (h)

24 >I68 168 168 168 168

nla 240 nla nla nla nla

&

EFa (me/mzh)

EF168 (me/m2h)

0.21

0.092

Ref 1 2 3a 3b 3c 3d


Note: AU EF, values are estimated by the first-order decay model: EF = EFo e d - k t ) . Refi 1. Molhave, 1982; Chamber conditions: lm3, 21°c, 40%RH, 1 ACH, L= 0.73 m2/m3(average). 2. Jensen et al., 1993; Sample preparation: Raw linoleum was hardened in air at 6 0 . 8 0 ~for ~ 2-3 weeks and then "rapped in bags and unwra ped before test; Pm3, SOLRDRH, 161 ACH, b498m2/m3. Chamber conditions: 3.5~103. Gunnarsen et al, 1994, Chamber conditions: a: 0.0509 m3. 22'~.50%RH,5ACH. d-12 m2/m3; b: 35x10" m3,2 2 ' ~ S .OLRDRH, 171ACH. b 5 1 4 m2/m3; c: 0.0509 m3, 22Oc. 50%RH, 61ACH. L=12 m2/m3; d: 28.5 m3, 22'~,5046RH. 2ACH. M . 4 2 m2/m3.

Analysis of linoleum emission data (Jensen et al, 1993) showed that the initial emission rate decay constants are about 0.004-0.005 h-' for propionic acid, hexanal, and nonanal. Gustafsson and Jonsson (1993) also reported that the linoleum emission factor decreased b about two-thirds from one-month to six-month, equivalent to a decay constant of 0.0003 h- . These values indicated that the emission decay of linoleum changed from short term tests to long term tests. Hence, the first-order decay model derived from short term emission data is inadequate to predict long term emission. The ilm-diffusion model developed by Jensen et al (1993) appeared to give a good fit to the linoleum emission data obtained from a six-week test.

7

Jensen et al. (1996) investigated the oxidative emission of linoleum. The key evidence for oxidation is the ratio between aldehyde emissions and the carboxylic acid emissions under flow of nitrogen and atmospheric air, respectively. Aldehydes are likely oxidized to become the corresponding carboxylic acids under atmospheric air, especially when humidity is high. The experimental result showed that the aldehydelacid ratio was much lower under atmospheric air than that under dry nitrogen. It is also found that the irritative odor of old used or damaged linoleum is mainly due to the oxidatively generated carboxylic acid.

In summary, VOC emissions from linoleum showed similar TVOC emission factors as those of wood products but lower than those of vinyl products. Long term emission of linoleum is characterized by the oxidative degradation, particularly in environment of high humidity. 5.4 Carpet Traditional carpets were woven on looms with plant and animal fibers. Today most carpets are made of synthetic fibers from petroleum sources, such as nylon, polyester, and

IR-C

CMEIAQ: Report 4.1 (08197)

polypropylene. Both natural latex from tropical rubber trees and synthetic latex such as styrenebutadiene rubber (SBR), are used for carpet backing. Latex backing is found to account for a significant part of VOC emissions from new carpet (Pleil and Whiton, 1990 and Singhvi et al., 1990). For instance, the odor threshold of 4phenylcyclohexene (4-PC), emitted from SBR backing is 0.002 mglm2h (Wokoff, 1996) which is even lower than odor threshold of hydrogen sulfide, one of the most initant compounds. The non-SBR carpets emit VOCs no less than SBR-backing carpets (Black et al., 1993a). Type of major VOCs emitted from carpet depends on the type of carpet, the type of latex backing. More specifically, Black et al. (1993a) indicated that the primary VOCs emitted from SBR-backed carpets were styrene and 4PC, while from nonSBR backed carpet were trimethyl pentane and acetic acid. Wokoff et al. (1996) detected 2ethylhexanol. nonanal, decanal, and 4-PCas the major VOCs from a SBR-backed nylon carpet. Kirchner et al. (1993) found that the VOCs emitted from a latex-backed carpet were aliphatic, aromatics, aldehydes, terpens, etc., while from a carpet glued to plywood were alcohols, ketones, aldehydes, aromatic, terpenes, acids, and esters. The latter were attributed to the plywood and glues. TVOC emission from carpets is in general lower than or equal to that of the other dry materials such as wood boards and vinyl products (Black et al., 1993b). It was reported that TVOC emission factors ranged from 0.006 mg/m2h to 0.6 mg/m2h ( levin, 1992 and Black, et al, 1991a). The existing emission data for both TVOC and individual VOCs are presented in Table 5.4. Horstman and Lipton (1996) found that the emission rate of carpet decayed in the fmt few days after installation, but the majority of VOCs were still detectable in ambient air 13 days after installation. Gunnarsen et al. (1994) reported that the emission factors of 2eth lhexanol from a polyamide fiber carpet in six different test chambers ranged from 0.04 mglm h to 0.9 mg/m2h. The emission factor tested in FLEC was the highest one. Sollinger and Levsen (1993) also reported that the emission factors of carpet sample tested in a 0.03 m3 and a 1 m3 chamber were very close, while tested in a 38 m3 chamber was different. The concentration in the 38 rn3 chamber rose slowly and reached a lower maximum value than in the large chamber. The authors attributed these results to the sink effect and the inadequate mixing in the 38 m3 chamber. Another experimental result showed that VOC emissions from carpet were enhanced by an increase of temperature from 2 3 ' ~to 3 5 ' ~and air velocity from 0.1 d s to 0.3 mls. A change of humidity from 0% to 50% also significantly affected VOC emissions from the carpet (Wolkoff, 1996). A comparison of the VOC emissions from a carpet with its edge sealed and unsealed indicated that the edge sealing had no significant effect on the VOC emissions (Sollinger and Levsen, 1993). An increase in the ozone level (> 30 ppb) in the indoor environment would increase the VOC emissions from carpets (Weschier, et al, 1992). These VOCs include &PC, 4-vinylcyclohexene, and styrene.

2'

Several studies have confumed that the VOC emissions from carpet are controlled by in-material diffusion (Wokoff et al., 1993b and Linle et al., 1994). The emission rate can be


correlated to the thickness of the carpet. The diffusion model based arp the Fick's Law was found to be suitable for predicting the VOC emissions frLn the cq (Little et al., 1994), whereas the first-order decay model appeared to be i n m u a t e for describing the entire emission process. Table 5.4 Emission factor of carpets

Polyurethanebacked Nylon, SBR-backed

PVC-backed

Polyurethane-backed Polyamide Fiber Wpet

Styrene Formaldehyde Vinyl Acetate 1,2-Ropa%diol 2-Ethythexanol 1.2-Di-ten-butyl4-methylphenol 2-Ethylhexan01 2-Nonenal

0.025-0.26 0.057 0.85 0.69 0.058 021 1.4-2.5 25

a0015 0.006

24 24 24 24 24

168 168 168 168 168

24

168

16 8 16 8

% %

0.0020.02 0.018 0.10 0.19 0.023 0.17

4 4 4 4 4

4 6 6

Note: All EF, values are estimated by the first-order decay model: EF = EFo exp(-kt). ReE 1. Black, 1990; Chamber conditions: 0.05m3, @c, 5O%RH, 1 ACH, U=O.OS-O.ZmIsec. 2. Blacket al.. 1991b; Chamber conditions: lm3, 21-, 40%RH, 1 ACH, LF 0.41 m2/m3. 3. Black el al., 1993a; Chamber conditions: 0.05m3 and 26m3,UOC, 5O%RH, IACH, L+.41 m2/m3. 4. Hodgson et al., 1993; Small chamber conditions: 0.0038m3, 23'~. 6.3ACH. dry N2, Is2.6 m2/m3,U