Ventilated chambers coefficients

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. 

Release rate coefficients measured in ventilated chambers at 9-11 m /m differed by 13% from release rate coefficients analyzed under modified 3IS desiccator conditions (nonventilated) for the same products when extrapolated to a loading of 21 m /m (Table III) (12). Release rate coefficients for particle board or piwood measured in a ventilated chamber at a loading of 1.4-1.6 m /m were 4-33% different from those measured in a desiccator at similar loadings (1.4-1.8 m /m ). 

A similar comparison indicated that release rate coefficients fo particle board plus plywood measured in the ventilated chamber were 14% higher than those measured in the desiccator at loadings of 3.0-3.4 m2/m3 (Table III). 

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). 

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

The reactor for radiation chemical synthesis with an agitator (about 200 rotations per minute) is located in the operation chamber. Inside the reactor there is a cavity for introducing sources of y-radiation. The role of the radiation source is played by 60Co in airproof stainless steel ampules the activity of 60Co radiation is about 3000 eq Ra. The consumption degree of the energy of radiation when the sources are placed in the cavity, or the radiation coefficient of efficiency, varies from 17 to 19%. The equipment is encased in a special box made of stainless steel and plexiglass the box has intensive ventilation. 

Coefficient (yg m 2 day b Ventilated Nonventilated Di fference Chamber Desiccator X... 

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. 

The equilibrium concentration and the mass transfer coefficient were then used to calculate the steady state concentration in a system with air exchange with the surroundings, using the model presented above. Tests in a 24 m3 climate chamber, in which temperature, relative humidity and ventilation rate could be varied, were run to check the agreement between the calculated and measured values. 

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See also in sourсe #XX -- [ ]

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