1.1 This test method covers personal or area measurements of formaldehyde in indoor air in the range from 0.01 to 17 mg/m (0.008 to 14 ppm v/v). Formaldehyde is collected in a passive diffusion sampler, and analyzed by a colorimetric method using 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH). The recommended sampling time is 15 min to 24 h.

1.2 The lower quantification limit of the MBTH test method is 0.03 [mu]g of formaldehyde per millilitre of absorbing solution used. A formaldehyde concentration of 0.01 mg/m (0.008 ppm v/v) can be determined in indoor air, based on using an aliquot of 5 mL of absorbing solution in the prescribed sampler for a period of 24 h and observing a minimum difference of 0.05 absorbance units from the blank when using spectrophotometer cells of path length 1 cm.

1.3 Water soluble aliphatic aldehydes give a significant positive interference (1, 2) nearly equal to formaldehyde on a molar basis. Further information on estimating potential and actual interferences from aliphatic aldehydes may be found in 6.2 and 10.1.7. Most other compounds which react to produce colored products are not gaseous or water soluble and, consequently, should not interfere.

1.4 The values stated in SI units are to be regarded as the standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Notes 1 and 2.