Terpene Emissions from Particleboard and Medium-Density Fiberboard Products

COMPOSITES AND MANUFACTURED PRODUCTS

TERPENE EMISSIONS FROM PARTICLEBOARD AND MEDIUM-DENSITY FIBERBOARD PRODUCTS

MELISSA G.D. BAUMANN† STUART A. BATTERMAN GUO-ZHENG ZHANG

bility, inability to concentrate, and sleepi- ABSTRACT ness. Trätek, the Swedish Institute of Indoor air quality problems resulting from emission of volatile organic compounds Wood Technology Research (Stockholm, (VOCs) have become an issue of increasing concern. Factors known to affect VOC levels Sweden), estimates that 7 to 10 percent of in indoor air include: ventilation rate, occupant activities, and emissions from building the Swedish population has suffered ill and furnishing materials. In this research, VOC emissions from particleboard and health as a direct result of poor indoor air medium density fiberboard (MDF) were measured in small stainless steel chambers (53 quality, caused in part by VOCs emitted L) during a 4-day period. A protocol was developed to obtain new and representative by building materials and furnishings (2). samples and to minimize contamination of the samples during collection, preparation, Because of increased emphasis on in- and shipment to the laboratory. Samples were collected from 53 of the 61 U.S. mills that door air quality, accurate information is produce particleboard and MDF. Each mill identified the predominant tree species used needed regarding the amounts and types to manufacture the panels. The laboratory tests were conducted at 45 percent relative of VOCs emitted from building materials, furnishings, cleaning products, and humidity and used a gas chromatograph and a mass selective detector to identify and other materials found or used in the in- quantify VOC compounds. The predominant compounds identified in emissions from door environment. Such information will the particleboard and MDF samples were terpenes and aldehydes. Small straight-chain allow building occupants, product manu- alcohols and ketones were also found. This study describes the terpene emission data. facturers, building designers and con- Quantified terpenes included a- and b-pinene, camphene, 3-carene, p-cymene, li- tractors, and regulatory and public health monene, and borneol. Terpene emissions accounted for between 7 and 21 percent of the agencies to make informed decisions total VOC emissions, calculated as a-pinene. The highest terpene emissions were about the products they use and recom- observed from particleboard samples manufactured from pines other than southern pine. mend. Increasingly, some product manu- For particleboard, terpene emissions were largely related to the extractive content of the facturers are advertising “low VOC” materials or materials suitable for use by wood species. The terpenes were almost completely absent in emissions from MDF people with chemical sensitivities. samples, which indicates that differences in the manufacturing of MDF compared with Building designers and contractors are the manufacturing of particleboard may have considerably affected emissions. After 4 now being asked to certify that new days, the terpene emissions from all particleboard samples decreased to between 20 and buildings will meet indoor air quality re- 70 percent of their initial values. quirements set by building owners. Ac- curate emissions information is needed to decide which materials will best meet D uring the past several decades, air concentrations include: eye and respira- those requirements while fulfilling struc- quality in homes and office buildings has tory irritation (including asthma), irrita- tural and aesthetic needs. become a matter of increasing concern. Indoor air concentrations of volatile organic compounds (VOCs) are often sig- The authors are, respectively, Research Chemist, USDA Forest Serv., Forest Prod. Lab., One Gifford Pinchot Dr., Madison, WI 53705-2398; Associate Professor and Post-Doctoral nificantly higher than outside due to VOC Associate, Environmental and Industrial Health Univ. of Michigan, 109 Observatory Dr., Ann emissions from building materials, fur- Arbor, MI 48109-2029. The use of trade or firm names in this publication is for reader nishings, and occupant’s activities. This information and does not imply endorsement by the U.S. Dept. of Agriculture of any product problem was exacerbated following the or service. The authors thank the USDA Competitive Grants Program for funding provided to this research program, the National Particleboard Assoc. for funding and assistance in energy crisis in the 1970s as homeowners obtaining samples, Linda F. Lorenz for her work in data collection for this project, and and builders improved the energy effi- Anthony H. Conner for his guidance in getting VOC research started at the Forest Prod. Lab. ciency of their buildings by decreasing air This paper was received for publication in March 1998. Reprint No. 8797. † Forest Products Society Member. exchange rates. Adverse health effects ©Forest Products Society 1999. associated with moderate and high VOC Forest Prod. J. 49(1):49-56.

FOREST PRODUCTS JOURNAL VOL. 49, NO. 1 49 The Washington State East Campus bonded with pMDI, and these products EXPERIMENTAL PROCEDURE Plus project (6) provides an example of are for specialized purposes. Emissions SAMPLE COLLECTION how these requirements affect planning. of VOCs potentially can arise from each FROM MILLS During the design and construction of of the materials that compose a panel, but Samples of particleboard and MDF four state office buildings, indoor air attention, until recently, has been on were collected by three National Particle- quality specifications were established emissions of formaldehyde from the UF board Association (NPA) employees dur- that limited VOC emissions from build- resins used to bind particleboard, MDF, ing routine visits to the mills. (In March ing materials and furnishings. To ensure and hardwood plywood. The focus has 1997, the NPA and the Canadian Parti- that these specifications would be met, recently shifted to a variety of VOCs. cleboard Association joined together to many of the building and furnishing ma- form the Composite Panel Association Earlier research (5, 13, 16, 17) identified terials were tested for VOC emissions (CPA)). Sample collection kits were pro- a wide variety of VOCs including ace- prior to installation. For example, speci- vided by FPL, and explicit sample han- fied office furniture systems could emit tone, benzene, hexanal, and toluene emit- dling instructions were given to each of no more than 0.05 ppm formaldehyde ted from composite wood products. the sampling personnel. To prevent expo- and 0.50 ppm total VOCs. Some of these compounds have not pre- sure to or loss of VOCs during shipping, viously been associated with wood prod- In the United States, there are no fed- 300- by 300-mm (12- by 12-in.) panel eral regulations to govern VOC concen- ucts, and there is no ready explanation for samples were sandwiched between two trations in indoor air. However, regula- their presence. Previous studies used pieces of the same panel, wrapped in tory agencies such as the Environmental various types of chambers, different ma- aluminum foil, double-bagged in poly- Protection Agency (EPA) and the Occu- terial loading ratios, a range of air ex- ethylene zipper bags, and placed inside a pational Safety and Health Administra- change rates, a variety of methods for mailing envelope prior to shipping. In- tion (OSHA) have shown an interest in sample collection and storage, and differ- formation about the product type, pre- ensuring that people are not adversely ent analytical procedures. These differ- dominant wood species, additives used, affected by indoor air in their homes and ences make comparison and interpreta- and manufacturing conditions was recorded at the time of panel sample collec- offices. Development of indoor air VOC tion of the published data difficult, if not tion. General information about each standards is complicated by the follow- impossible. The identification and quan- panel, including resin type and wood ing factors: 1) correlations between prod- tification of emissions from wood prod- species, was provided to FPL along with uct emissions and indoor concentrations ucts (and other materials) should use the panel samples. Sampling was blind in are not straightforward; 2) many VOCs standardized methods as called for by that FPL researchers were not given in- result from occupant activities, including many investigators in the United States formation identifying the individual mill smoking, use of cleaning products or per- and abroad. or manufacturer of each sample. fumes, and cooking; and 3) detection of To answer questions about VOC emis- Panel samples were collected at the specific VOCs at low concentrations sions from wood composite products, we does not indicate whether or not they will mills from March to June of 1997. Upon undertook a study of emissions from un- receipt at FPL, the samples were logged have long-term health effects. finished particleboard and MDF pro- and placed in storage at 2°C until testing Composite wood products such as par- duced in the United States. A similar commenced. A total of 57 particleboard ticleboard, hardwood plywood, and me- study of Canadian-produced products and MDF panel samples were collected, dium density fiberboard (MDF) are has been completed by researchers at including duplicates from four mills. All widely used in indoor products (i.e., sub- Forintek Canada (A.O. Barry, 1995, un- panels were bonded with UF resin, and flooring, door cores, cabinets, paneling, published data). In our study, small, the products were divided into nine prod- and furniture.) In 1994, combined ship- stainless steel chambers were used to uct-species groupings based on manufac- ments of particleboard and MDF in the 8 2 house small samples of wood products turer reports of predominant species United States totaled almost 5.4 × 10 m under controlled environmental condi- groups used at the mills: southern pine (19-mm basis) (15). With the broad use particleboard (22 samples), other pine of composite wood products in modem tions. Wood samples were collected di- rectly from the mills using a sampling particleboard (8 samples), Douglas-fir homes and offices, there are concerns particleboard (4 samples), hardwood protocol developed by USDA Forest that emissions from these products could particleboard (4 samples), other particle- Service, Forest Products Laboratory (FPL) have a significant impact on indoor air board (1 sample), southern pine MDF (6 quality. researchers, thus decreasing the possibil- samples), other pine MDF (5 samples), Composite wood products are fairly ity of postmanufacture contamination. hardwood MDF (5 samples), and other simple combinations of wood and water- Samples were collected and evaluated MDF (2 samples). Duplicate panel sam- based adhesives. The adhesives are com- from 53 of the 61 mills in the United ples, included in the numbers above, posed of either urea-formaldehyde (UF) States that manufacture particleboard were provided for southern pine particle- or phenol-formaldehyde (PF) resin, inor- and MDF. Most mills not included in this board, hardwood particleboard, southern ganic components that act as catalysts, study either produce specialized prod- pine MDF, and other pine MDF. and other minor components (i.e., wax.) ucts or use materials that are atypical of LABORATORY Increasingly, polymeric methylene diiso- the particleboard and MDF industries. SAMPLING SCHEDULE cyanate (pMDI) is used to bond oriented This study details the evaluation of ter- The testing series was a 5-day cycle, strandboard (OSB) products. However, pene emissions from these particleboard consisting of 1 day of blank runs in the few particleboard and MDF products are and MDF products. chamber and 4 days of collecting and

50 JANUARY 1999 TABLE 1. - Summary of chamber conditions during testing. Parameter Value Chamber volume 0.053 m3 Chamber air flow 0.001 m3/minute (1.13 air changes/hr.) Temperature 23±1°C(73±1°F) Chamber humidity 45% ± 5% Sample area 0.021 m2 Loading ratio 0.40 m2/m3 GC sample volume 315 mL

analyzing air samples. On the first day, prior to putting specimens into the chambers, blank runs were performed for each of the empty chambers while clean, humidified air flowed through the chamber at a rate of 1 L/minute. Wood panel sam- Figure 1. – Automated volatile organic compound analysis system (mfc = mass ples were removed from the cold room, flow controller; rm = rotameter; sv = sampling valve). and a 102- by 102-mm test specimen was cut from each of the center panels, dis- carding the outer 25.4 mm from each sample panel and the outer panels used let ports consisted of tubes that extended gas chromatograph (GC) (Hewlett during shipping. To minimize edge emis- to within 2 cm of the bottom of the cham- Packard 5890 II, Palo Alto, Calif., with sions, specimens were edge-sealed by ber. Holes were distributed along the electronic pressure control). The VOCs brushing the edges with two coats of a length of the tubes to assure adequate were cryofocussed at the head of the GC saturated solution of sodium silicate and mixing of the inlet air with chamber air column at -100°C. The column head was left to dry overnight in a room main- and to assure that air samples collected at then heated to 150°C within ~ 15 seconds tained at 23°C (73°F) and 43 percent the chamber outlet were an average of the and held at that temperature for 3 minutes chamber air. relative humidity (RH). to inject the VOCs into the GC. A clean air supply to the chambers was The specimens were then placed into During separation of the VOCs, the generated by passing house-compressed nine of the chambers, leaving one cham- GC column (EC-5, 30 m by 0.25 mm, ber empty to serve as a control, and the air through sorbent towers and a catalytic oxidation unit. A portion of the dry, puri- 25-µm film thickness, Alltech Associates, time was recorded. The chambers were Inc., Deerfield, Ill.) was held at -20°C for closed, and clean humidified air flowed fied air was humidified using a tempera- 5 minutes, then heated to 120°C at a rate through the chambers for the next 4 days. ture-controlled impinger containing hy- drocarbon-free water and blended with of 10°C/minute, and finally held at On days 1, 2, and 3 of the 4-day speci- dry air to produce 45 ± 5 percent RH. The 120°C for 5 minutes. This program men testing (at approximately 24, 48, humidified airstream was then distrib- achieved adequate separation of the com- and 72 hr.), air samples were drawn from uted to the chambers. pounds expected from wood products. each chamber and analyzed for VOCs. The air sampling and analysis procedures Chamber outlets led to a rotary switch- After the compound passed through the are described in the following sections. ing valve that allowed sequential sam- GC, a mass selective detector (MSD) In addition, on day 2 (48 hr.), air samples pling of air in the chambers without hav- (Hewlett Packard 5972) at the GC col- were collected on 2,4-dinitrophenylhy- ing to connect or disconnect tubing. All umn outlet was used to detect the various drazine cartridges for aldehyde and ke- materials in contact with the sample air VOCs. tone analysis. This information will be were constructed of stainless steel, glass, The following target compounds were reported in a subsequent publication. or Teflon. Chamber conditions during based on a review of the literature (5,9, testing are summarized in Table 1. CHAMBER SYSTEM 14,16,17,19) and include the major ter- Figure 1 depicts the experimental VOLATILE ORGANIC COMPOUND penes, aldehydes, and alcohols that have chamber system (3,4), which was con- COLLECTION AND ANALYSIS been associated with wood products: structed in accordance with ASTM When a particular chamber was se- D5116-90 (1). The 10 electropolished lected using the sampling valve, 315 mL acetaldehyde heptanal pentanal stainless steel test chambers had a nomi- of air from that chamber was passed acetic acid heptane pentane nal volume of 53 L and were located through a cryoconcentrator (CDS Ana- acetone 2-heptanone 1-pentanol within a conditioned room maintained at lytical, Peakmaster EV, Oxford, Pa.) at benzaldehyde 3-heptanone a-pinene 23°C (73°F). Clean, humidified air was -100°C where VOCs condensed out of benzene hexanal b-pinene metered into each chamber at 1.0 L/min- the air sample. Subsequently, the cryo- borneol isopropanol toluene ute, providing 1.13 air exchanges per concentrator trap was heated to 150°C butanal limonene m-xylene hour to each chamber. The inlet and out- for 5 minutes to transfer the VOCs to the 2-butanone nonanal o-xylene

FOREST PRODUCTS JOURNAL VOL. 49, NO. 1 51 camphene octanal p-xylene mass spectral library (12); however, con- all terpenes were between 0.06 and 0.14 3-carene octane centrations were not quantified. µg/m3. Based on replicate samples, re- p-cymene 1-octenal GC-MSD CALIBRATION producibility of VOC measurements was Acetaldehyde and acetone were de- Calibration curves for the target com- typically 10 to 25 percent. Target com- tected and quantified by using 2,4-dini- pounds were constructed using standards pounds were not detected in blank tests. prepared from neat VOCs in pentane so- trophenyl-hydrazine with subsequent RESULTS AND DISCUSSION lutions, direct injections into the GC in- HPLC analysis. They are not included jection port, and cryofocussing on the Among the target compounds, the pre- in the TVOC calculations presented in GC column. Quantitation was based on dominant VOCs emitted from the parti- this paper. the concentrations of particular ions rep- cleboard and MDF samples were the ter- The VOCs were identified and quanti- resentative of the compounds being ana- penoid compounds and several straight- fied using retention time and a spectral lyzed. Careful selection of the ions al- chain aldehydes, including pentanal, library developed for each target com- lowed compounds with close GC elution hexanal, and t-2-octenal. Several nontar- pound. Nontarget compounds were iden- times to be quantified without interfering get compounds, including heptanol, 2- tified by comparison with a standard with one another. Limits of detection for pentylfuran, camphor, fenchone, and fenchol, were identified in numerous samples. Aromatic and halogenated TABLE 2. – Average 48-hour emission factors for monoterpenes, as measured by GC-MSD, ,for compounds, which have been reported particleboard samples listed by manufacturer-designated predominant species group. by other researchers (5,16), were not de- Average 48-hour emission factors tected in any of the samples. Detected volatile Southern pine Pine Hardwood Douglas-fir Other organic compound (22)a (8) (3) (4) (2) The 48-hour (day 2) concentrations of (µg m-2h-1) monoterpenes from the particleboard a-pinene and MDF samples are summarized in Camphene Tables 2 through 4. Emissions from sam- b-pinene ples after 48 hours in the chamber were 3-carene chosen for detailed analysis, so that re- p-cymene sults could later be compared with the Limonene aldehyde and ketone data collected on Fenchone 2,4-dinitrophenylhydrazine cartridges. Fenchol Results from all days showed similar pat- Camphor terns in differences between the species Borneol groupings and product types. In the 48- Total terpenes hour tests, the target terpenes accounted d TVOC for 7 to 21 percent of the total VOC Terpenes in TVOC (%) emissions (calculated as a-pinene) from a Values in parentheses indicate number of samples. the particleboard samples. There were b ND = not detected in any of the samples. significant differences among the parti- c NQ = detected in some samples, but not quantified. d TVOC = sum of compounds quantified as a-pinene based on their total-ion-current areas, It does not cleboard samples in the types of terpenes include compounds that were not quantified by GC-MSD, including formaldehyde, acetaldehyde, and emitted. Terpenes were almost entirely acetone. absent from the MDF samples.

TABLE 3. – Median, minimum, and maximum emission factors for emissions from particleboard after 48 hours in the test chamber: Southern pine (22)a Pine (8) Detected Hardwood (3) Douglas-fir (4) terpene Medianb Low High Median Lowc Highc Median Low High Median Low Highc ------(µgm-2h-1)------a-pinene Camphene b-pinene 3-carene p-cymene Limonene Borneo1 TVOCd a Values in parentheses indicate number of samples. b Median of nonzero values. Numbers in parentheses are the total number of samples that had detectable emissions. c All values in these columns are from a single sample. d TVOC = sum of compounds quantified as a-pinene based on their total-ion-current areas. It does not include compounds that were not quantified by GC-MSD, including formaldehyde, acetaldehyde, and acetone.

52 JANUARY 1999 SPECIES VARIATION TABLE 4.–Average 48-hour emission factors for monoterpenes, as measured by GC-MSD, for medium AND EMISSION VARIABILITY density fiberboard samples by manufacturer-designed predominant species group. Terpenes are naturally occurring com- Average 48-hour emission factors pounds (8) that are made up of isoprene Detected volatile Southern pine Pine Hardwood Other building block units (Fig. 2). Monoter- organic compound (6)a (5) (5) (2) penes constitute a considerable portion ------(µg m-2h-1)------of the extractive content of softwood spe- a-pinene NDb ND ND ND cies and are responsible for much of the Camphene ND ND ND ND characteristic odor of the softwoods. The b-pinene ND ND ND ND terpene content of softwoods varies with 3-carene ND 2 ND ND species (Table 5) and depends upon the p-cymene 0.1 0.5 0.4 ND locality and growing conditions. Com- Limonene ND 2 5 ND parison of the predominant terpene ex- Fenchone NQc ND ND ND tractives in Table 5 with the chamber Fenchol NQ NQ ND ND data in Table 2 and Figure 3 indicates Camphor NQ NQ ND ND that emissions change in accordance with Borneol 2 7 2 4 the extractives content of the species Total terpenes 2.1 11.5 7.2 4 group from which the panels are manu- TVOCd 878 373 122 205 factured. For example, in the southern Terpenes in TVOC (%) 0.2 3 6 2 pine particleboard samples, the predomi- a Values in parentheses indicate number of samples. nant terpene emissions were a-pinene, b- b ND = not detected in any of the samples. pinene, and borneol, while 3-carene was c NQ = detected in some samples, but not quantified. not detected. The extractives of southern d TVOC = sum of compounds quantified as a-pinene based on their total-ion-current areas. It does not pine species are not known to include 3- include compounds that were not quantified by GC-MSD, including formaldehyde, acetaldehyde, and carene (11). In contrast, particleboard acetone. samples classified as other pine emitted high concentrations of 3-carene along with the other terpenoid compounds. The other pines are generally western pine species, including ponderosa and lodgepole pine, and extractives of these woods contain substantial percentages of 3- carene (7). a-Pinene Camphene b-Pinene 3-Carene The variability seen in the species groups listed in Tables 2 and 3 is consistent with extractive variations in species. The southern pine group is made up of closely-related pines including loblolly, slash, and shortleaf pines. The terpene proportions found in these woods are similar. Consistent with these similari- ties, the relative standard deviations for p-Cymene Limonene Borneol all the emitted terpenes from southern pine paticleboards were between 44 and 78 percent. However, the other particleboard samples yielded much higher relative standard deviations (generally above 100%). The other pine group is made up of a variety of species that have considerably different extractives contents. For Camphor Fenchone Fenchol example, ponderosa pine contains 0.35 percent turpentine, whereas in lodgepole pine, the turpentine fraction is 0.2 per- Figure 2.–Terpenes identified in emissions from particleboard and medium density cent (9). The variation in total terpene fiberboard produced in the United States. content among species probably ac- counts for differences in the emissions from samples within the same product- lacking in monoterpenoid compounds. fir and hardwood emitted significant species group. Most panels classified as primarily levels of terpenes. These samples had Douglas-fir contains lower levels of Douglas-fir or hardwood emitted little or high terpene emissions at sampling on extractives including terpenes than pines, no terpenes. However, one sample each days 1, 2, and 4 of sample testing (24, 48, and hardwood extractives are generally of the particleboard manufactured with and 96 hr.), indicating that this was not a

FOREST PRODUCTS JOURNAL VOL. 49, NO. 1 53 statistical or measurement error. Discus- PARTICLEBOARD In the fiberboard industry, chips are con- sions with personnel at the Composite COMPARED WITH MDF verted to fibers using a pulping process Panel Assoc. (Gaithersburg, Md.) indi- In most particleboard samples, emis- where they are reduced by mechanical cated that this could be the result of some sions of terpenes such as the pinenes, action aided by thermal softening of the pine woods being used in an otherwise 3-carene, p-cymene, and borneol were lignin-rich middle lamella between wood predominantly hardwood or Douglas-fir readily apparent as expected. However, cells. During this process, the tempera- mill (Dan Hare, Composite Panel Assoc., most of these compounds were entirely ture in the pressurized refiner is generally 1997, personal communication). absent in tests of MDF samples (Table 4). held between 160° and 185°C. This high- temperature process may drive terpenes from the furnish resulting in lower emis- TABLE 5. – Extractive compositions of various softwood species (7, 11). sions by the product. Consistent with this explanation, the terpenes with the lower Percentage of compound in extractives boiling points, such as a- and b-pinene a-pinene Camphene b-pinene 3-carene p-cymene Limonene (boiling points of 155° and 165°C re- Loblolly pine spectively), were completely absent from Slash pine the MDF emissions, whereas the higher Ponderosa pine boiling terpenes, such as limonene and Lodgepole pine borneol (boiling points of 176° and Douglas-fir 212°C respectively), were present in some of the samples. In comparison, ele- vated temperatures and steam pressure are not used in the processing of particleboard fiber.

CONCENTRATION DECREASES WITH TIME The chamber concentrations of terpenes emitted from both particleboard and MDF decreased during the 4 days in the chamber. Decreases ranged from 20 to 80 percent, with borneol, the highest boiling point compound, consistently showing the smallest drop. Figure 4 shows the trends for terpenes emitted from the southern pine particleboard alpha- beta- Camphene 3-Carene p-Cymene Limonene Borneol samples, which are representative of the Pinene Pinene general trends observed for all samples. An exponential decay has been observed Figure 3. – Average emission factors of monoterpenes measured at 48 hours for outgassing of many products, and emitted from particleboard samples. Samples are grouped by manufacturer-desig- similar results are expected for VOC nated predominant species used to make the product. emissions from particleboard and MDF panels. However, additional tests at long holding times (1 month or more) are needed to estimate the long-term emission characteristics. The sampling and storage protocols should yield results that are representative of emissions expected immediately after use of new panels that have been stored in stacks or wrapped bundles. This is a worst-case scenario. Emissions from aged and ventilated panels are expected to be considerably lower than those reported in this study. Also, the coatings or laminates often used over composite wood products would further decrease emissions from the wood products.

NONTERPENE EMISSIONS In addition to terpenes discussed here, Figure 4. – Reduction of emission factors with time, normalized to 24-hour test, several other types of compounds were based on average emissions from 22 southern pine particleboard samples. emitted by particleboard and MDF pan-

54 JANUARY 1999 TABLE 6. – Number of samples containing various nonterpene emissions from particleboard and medium density fiberboard identified in chamber tests. Tentative identification based upon MS spectral library. Southern pine Other pines Hardwood Douglas-fir Boiling Particleboard MDF Particleboard MDF Particleboard MDF Particleboard a Compound point (22) (6) (8) (5) (3) (5) (4)

Aldehydes Formaldehyde Acetaldehyde Propanal Butanal Pentanal Hexanal Heptanal Benzaldehyde Octanal t-2-octenal Nonanal Ketones Acetone 2-heptanone Alcohols 1-pentanol 1-heptanol Other Acetic acid 2-pentylfuran a Values in parentheses indicate number of samples.

els (Table 6). Of particular interest, included many monoterpenes. The MDF straight-chain aldehydes were present in emissions were much lower and included a large number of samples. Although al- few terpenes. In general, particleboard dehyde concentrations were not quanti- emissions were correlated with the re- fied, it is clear that aldehyde emissions, ported terpene content in the wood ex- most notably hexanal, exceeded those of tractives of the species used to manufac- terpenes. While there are no reports in the ture the panel. However, emissions literature of these small, straight-chain greatly varied for similar products made aldehydes being present in the extrac- from the same wood species, but manu- tives of wood, there are reports of alde- factured by different mills. Terpene emis- hydes being emitted during the manufac- sions decreased considerably during the ture of wood products and from the wood 4 days they were in the test chamber. The products themselves (10, 18; A.O. Barry, protocol and results reported here should 1995, unpublished data). Aldehyde emis- provide representative emission rates for sions appear to result from the oxidation new particleboard and MDF panels. This of some wood component, but not from study did not address the issue of the additives or adhesive resins. The oxida- effects of coatings or laminates, which tion mechanism is not known, but could are often used over composite wood be attributable to thermal, enzymatic, or products and which would alter the emis- microbiological processes. sion characteristics considerably. CONCLUSIONS LITERATURE CITED This study sampled particleboard and MDF products from more than 85 percent of U.S. MDF manufacturers. The VOC emissions determined in laboratory chamber tests indicated that terpene emissions from these products depend strongly on the wood species and the type of product. Particleboard emissions

FOREST PRODUCTS JOURNAL VOL. 49, NO. 1 55 56 JANUARY 1999