Abstract
A passive sampling device based on the principle of diffusion has been developed for the determination of formaldehyde in ambient air. The sampler consists of a capped glass tube (with approximate dimensions of 2.4 × 9 cm) containing a glass-fiber filter treated with NaHSO 3. In the field, the device collects a sample by being uncapped for a specified sampling time. After being recapped and returned to the laboratory, the filter is analyzed by the chromotropic acid (CTA) method. Laboratory validation studies were conducted by exposing the sampling devices for 1 week to dry formaldehyde gas generated by passing trioxane vapor over an acid catalyst bed. In these tests, formaldehyde concentrations ranged from 0.05 to 0.80 mL/m 3. Reproducibility was excellent, with relative standard deviations averaging 5.4% for five constant concentrations. The lower detection limit was determined to be 3.6 mL/m 3 h. In an occupational environment an 8-h sample would be sufficient to detect compliance with the OSHA permissible exposure limit of 3 mL/m 3; in a residential environment a 1-week sample would allow detection of 0.025 mL/m 3 for indoor air quality audits.
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