Formaldehyde release rate coefficients

Pickrell JA, Mokler BV, Griffis LC, et al. 1983. Formaldehyde release rate coefficients from selected consumer products. Environ Sci Technol 17 753-757. 

Formaldehyde Release Rate Coefficients from Selected Consumer Products... 

In these studies, formaldehyde release rate coefficients were measured for different consumer products using two methods. 

Each of these products was conditioned at room temperature, and 100% relative humidity (RH) (31 to 67 days). Formaldehyde release was measured as described H, 8, 15). A modified JIS desiccator procedure was used, and formaldehyde was quantitated using a pararosaniline procedure (15, 16). Formaldehyde release rate coefficients were calculated (15). An average coefficient of variation of 16% was obtained for this measurement (15). Samples displaced less than 12% of the chamber air (15). 

Unwashed new clothing samples (Table IIC), fiberglass insulation products with formaldehyde resins (Table IID), paper products (Table HE), fabrics (cotton, nylon, olefin, and blended) (Table HF), and carpets (Table HG), had substantially 3 to > 100 fold) lower formaldehyde release rate coefficients, as measured by this method, than did pressed wood products or urea formaldehyde foams (1, 15). 

Table III. Comparison of Formaldehyde Release Rate Coefficients in Ventilated Chambers and Nonventilated Desiccators...

Extractable Formaldehyde (mg/100 g) Loading (m /m ) Formaldehyde Release Rate Coefficient (vg m 2 day b Calculated Loading Effect ... 

This number is the multiple of the first two columns (Formaldehyde release rate coefficient) (loading). 

Formaldehyde release rate coefficients measured in desiccators were similar to those determined in the dynamic chamber at similar loadings. Initial formaldehyde release rate coefficients for one sample each of particle board and plywood measured at 11.4 and 8.6 m /m in these chambers at one volume change per hour were 2-fold higher than those measured in desiccators at higher loadings (8, 15, 17). However, when the release rate coefficients were adjusted for differences in loading, the calculated release rate coefficients were similar to those measured in desiccators (8, 15, 17). 

Formaldehyde (CH2O) release was measured for seven types of consumer products pressed wood, urea formaldehyde foam materials, clothes, insulation, paper, fabric, and carpet. A modified Japanese Industrial Standard (JIS) desiccator test was used to measure release rate coefficients and to rank 53 products. Ten pressed wood products and five urea formaldehyde foam products showed the highest CH2O releases (1-34 mg m 2.day"b The remainder, representing all product types, had lower releases ranging from 680 yg m 2.day to nondetectable levels. In other studies, CH2O release was measured in a ventilated chamber for single samples of particle board, plywood, insulation, and carpet. 

As measured by the modified JIS desiccator procedure, pressed wood products had the highest release rate coefficients expressed as a function of surface area (Table IIA) of the various sample types tested. Release rate coefficients from urea formaldehyde foam products were comparable to those of pressed wood products (Table IIB). Products labelled substrate (sub 1, sub 2, and sub 6) were experimental foams. The drywall that had been placed next to the foams (Number 1, 2, or 3) for more than 1 week in a configuration similar to that in a building released a moderate amount of formaldehyde. 

In dynamic (ventilated) chambers, release rate coefficients were increased by a factor of 4.4 for particle board and 2.2 for plywood at loadings of 1.4-1.6 m /m over values at loadings of 9-11 m2/m3 (Table IV). Increased pressure of formaldehyde in the chamber was associated with reduced release of formaldehyde from wood products, as indicated by comparing equilibrium concentrations of formaldehyde (H). 

Formaldehyde release rates were measured using multiple consumer products in a dynamic chamber. Particle board and plywood had high formaldehyde specific release rate coefficients. Combined plywood and particle board had a release rate 68% of the sum of the two products and 91% of the particle board release (Table V). When particle board was combined with insulation, the combined release rate was 71% of the sum of the separate release rates and 73% of the particle board release. Particle board and carpet combinations gave similar results. 

A good correlation was noted between release rate coefficients at loadings of 1.4-2.8 m2 of product surface area/m of chamber volume and formaldehyde extractable into toluene (Table V r = 0.999 p = < 0.001). Total extractable formaldehyde was quite low in both carpet and fiberglass insulation (0.5-1.6 mg/100 g of material) relative to that in plywood or particle board (22-55 mg/100 g of material) (Table V) (12). 

Pressed wood products and urea formaldehyde foam products had much higher release rates than those from most of the other products tested. Similar release rates have been observed by others (19). More than half of the products tested had very low release rate coefficients, and this included individual samples from six of seven of the types of products. Products equilibrated at 100% RH prior to the measurement were used to measure formaldehyde release. This equilibration may have removed a variable amount of formaldehyde (8, 14-17). 

The relative ranking for each type of product on the basis of rate of release of formaldehyde per unit surface area was pressed wood products z formaldehyde foam clothes z insulation products z paper products > fabric > carpet. Considering the surface area of each type of product likely to be present in houses and the relative release rate coefficients. 

Reduced sample loadings in the dynamic chamber led to decreased formaldehyde concentrations in the chamber as noted or predicted previously by others (17, 20-22). This resulted in increased release rate coefficients (yg m 2 day"b. Samples analyzed at 1.4 and 1.6 m2 of product surface area/m of chamber volume chamber loadings had formaldehyde chamber concentrations of 28-32% of the calculated equilibrium air concentrations of formaldehyde (17), suggesting better relative ventilation than that at higher chamber loadings. 

This ester resembles its methyl homologue in possessing three modes of decomposition [131]. It also supports a self-decomposition flame, the multiple reaction zones of which are clearly separated at low pressures [122, 123, 125]. Temperature and composition profiles in the low-pressure decomposition flame have been measured [133]. The products include formaldehyde, acetaldehyde and ethanol with smaller amounts of methane and nitromethane. The activation energy derived from the variation of flame speed with final flame temperature was 38 kcal. mole", close to the dissociation energy of the RO—NO2 bond. The controlling reaction is believed to be unimolecular in its low pressure regime, and the rate coefficient calculated from the heat-release profile is... 

If one ranks the various consumer products in this survey based on their release coefficients per unit of surface area, more than 45% of the samples (24 samples) had very low offgassing rate coefficient (< 100 pg of formaldehyde released (m of... 

In cooperation with DSM, MCN developed a method of measurement for the determination of the formaldehyde release from particle board, based on a theorie for mass transfer, implying that under steady state conditions the emission of formaldehyde of a given particle board can and should be defined by two parameters of the particular board. These two parameters are (1) Ce defined as the equilibrium formaldehyde concentration (with ventilation rate 0") and (2) kgg defined as the overall mass transfer coefficient of the board. In (ideal mixed) climate rooms the stationary formaldehyde... 

The concentration of formaldehyde in the air of a room containing particleboards, will depend on the content of formaldehyde in the boards and on the rate of its release. The formaldehyde content of a particleboard is determined by the binder used to manufacture the board and a number of production parameters. The release rate is affected by the temperature and the relative humidity of the surrounding air, but also by some of the physical properties of the board. The most important one probably is the diffusion resistance of the surface layer, which may be expressed by means of a mass transfer coefficient. 

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