Formaldehyde emission discussion

Environment, toxicity With durable flame retardancy, formaldehyde emission during curing and after finishing, phosphorous compounds in the waste water Antimony oxide and organic halogen donators (DBDPO and HCBC) are discussed as problems (for example possibility of generating polyhalo-genated dioxins and furanes)... 

However, on an empirical basis, the range of potential emission behavior is reasonably well known, and the correlation between emission measurements on product samples under standard conditions can now be related well to the expected range of indoor air levels under various user conditions. This subject is discussed in two separate chapters. Thus, quality control depends on formaldehyde emission measurements. This can be done by determination of the formaldehyde content of the finished product, or by measuring air levels around the product. 

The formaldehyde emission rate has been discussed in the preceding section. The product finish has a substantial influence on emission, as shown in the section below. 

Roffael (15) measured formaldehyde emissions from a phenolic particleboard using the WKI-Method which involves suspending small samples over 50 cm of distilled water in tightly closed polyethylene bottles and measuring formaldehyde levels in the water after varying times. Temperatures were maintained at 42 C. This work indicated that formaldehyde release from the phenolic particleboards ceased after a relatively short reaction period (approximately 96 hours). This finding is consistent with the resin stability considerations discussed previously under theoretical considerations. 

Factors to be considered in this paper include (a) the degree to which formaldehyde emission rate from wood systems is controlled by diffusion processes, (b) the contribution of resin hydrolysis to emission rate, and (c) the contribution of formaldehyde-wood states to emission rate. In the following, therefore, I first summarize briefly the reported evidence regarding diffusion control and resin hydrolysis in actual bonded wood products. Thereafter, I present and discuss some of my own recent experiments on wood systems that attempted to shed additional light on the questions of resin hydrolysis and the emission mechanism more generally. 

After a discussion of mechanisms for the liberation and subsequent emission of formaldehyde from particleboard, methods to assess the extent of these processes are described. Data are presented for the formaldehyde emission from particleboard with various surface treatments. These data were obtained by a laboratory method and by large climate chamber measurements and show that some of the surface treatments studied constitute very efficient diffusion barriers and considerably reduce the formaldehyde emission rate. 

The first three chapters deal with particleboard, medium density fiberboard, hardwood plywood, and softwood plywood, the four most widely used wood panel products. Chapter four compares these products with other consumer products. Chapters five through seven explain the basic chemistry of formaldehyde with cellulose and wood components and provide a current understanding of the nature of liquid urea-formaldehyde adhesive resins. The next two chapters present new analytical methods that might become useful in the future. Chapters eight and eleven through sixteen explain the complex nature of the latent formaldehyde present in the products and its correlation to formaldehyde emission from wood products. Chapters fifteen and sixteen describe currently popular formaldehyde reduction methods. The last two chapters discuss the problems involved in reducing formaldehyde emission by regulating air levels or source emissions. 

Methanol is expected to oxidize to formaldehyde, both during combustion and after emission to the atmosphere. As discussed in Chapter 6.H, OH reacts with methanol primarily at the methyl group ... 

HVAC Materials Ventilation duct liners also react with ozone forming formaldehyde, acetone and C5—Ci0 aldehydes. Morrison et al. (1998) subjected new and used duct liners, air filters, sealants, sheet metal and other HVAC materials to ozone in small chambers. They observed secondary emissions of C5—Ci0 aldehydes from a new duct liner, a neoprene gasket and duct sealants. They predicted that secondary emissions from these materials could increase indoor aldehyde concentrations to levels comparable with odor thresholds. As will be discussed later, soiled HVAC materials also generate secondary products. 

Personal computers (PCs) are important sources of VOCs in office and homes (Bako-Biro et al., 2004).Thus, the TVOCs emission rate per PC observed in a glass chamber study was as high as 486.6 pg/h while individual emission rates for toluene and phenol were 47 and 63 pg/h respectively. Other prominent chemicals emitted by PCs include, 2-ethylhexanol, formaldehyde and styrene (Bako-Biro et al., 2004). (See Chapter 17 for a more detailed discussion of VOCs in electronic devices.)... 

Brown (2000) evaluated VOC emissions from two of these products, as summarized in Table 16.6. Paint 1 was claimed to use orange peel oil as its base. It exhibited very high and fast-decaying emissions of C7-C10 alkane and limonene, with EF at 2 hours of 70000 and 120000 tgrn 2 h 1, respectively. Paint 2 was claimed to be based on vegetable oils and was virtually nonemitting at application, but emitted several malodorous aldehydes (including formaldehyde) and little else from 8 hours after application. This was considered to show an auto-oxidation reaction occurred for this product, similar to that observed with the alkyd enamel paint discussed earlier. 

In contrast to this anti-maser action in formaldehyde, H20 and OH are observed in maser emission. Collisional or radiative pumping is thought to maintain the population inversion between the two levels. As photons pass through the cloud, they are amplified by stimulated emission of radiation. The maser emission of H20 is possibly the most unusual of the observed anomalies, both from an astrophysical and a spectroscopic point of view. This is not the place to discuss details of the various models suggested, we would refer to concentrate on some of the general features observed in the maser emission spectra. 

It is important to note here that higher temperatures probably increase emissions from phenolic panels simply by accelerating the release of that small amount of residual formaldehyde that originates from the adhesive and subsequently becomes adsorbed to the wood substance and water in the wood. Because phenolic resins are very stable chemically, any temperature-related increase in emissions would not be expected to be associated with resin degradation. Consequently, temperature would be expected to exert much less influence on emissions from panels which have been aired out than from fresh panels. Indeed, this trend is shown by the data, as discussed below. 

The five emissions considered for this analysis include mercury, benzene, toluene, formaldehyde, and hexane. The amounts of these emissions are of interest, and an analysis of Table 3.1 presents a scenario where it appears that mercury emissions for the mercury process will be traded off versus no mercury emissions and higher other toxic emissions for the diaphragm process. To compare the pollutants, the analysis was performed as if aU pollutants for 1 year were released at the same time and the toxicity potentials for the pollutants can be added together as PEI, as introduced by the WAR algorithm. Guidehnes for considering when it is appropriate to consider adding chemical doses and responses are discussed in documents by the US EPA [66,67]. 

Aldehydes are emitted from a variety of anthropogenic sources associated with natural gas and petroleum combustion (for examples, see tables I-C-2 and I-C-3). Winer et al. (1992) have discussed direct emissions of aldehydes from biogenic sources. They are also important intermediates in the oxidation of directly emitted organic compounds. For example, formaldehyde, CH2O formed in the reaction of CH3O with O2... 

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