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Problems with the Performance of Passive Monitors for Formaldehyde

The existing standard for occupational exposures to formaldehyde, promulgated by the Occupational Safety and Health Administration, established a "permissible exposure limit" for formaldehyde of 3 parts per million as an 8-hour time-weighted average concentration (TWA) (1). Subsequently, when formaldehyde was recognized as a potential occupational carcinogen, the National Institute for Occupational Safety and Health (NIOSH) recommended that exposures be reduced to the lowest feasible levels (2). New technologies have emerged for detecting formaldehyde in the environment; a principal innovation is the "passive monitor."

Passive monitors, produced as badges to be worn on clothing or affixed to a wall, are devices that sample the environment for hazardous substances, such as formaldehyde. They are "passive" in that they rely on unassisted molecular diffusion of the environmental agent in the air onto a sorbent material; the sorbent is then subjected to chemical analysis to determine the amount of formaldehyde adsorbed. This differs from the established practice of sampling, which utilizes a mechanical air pump to direct air, at a known flow rate, over a sorbent material, or through a liquid contained in an impinger; the material in the impinger is then quantitatively analyzed for formaldehyde. From these results, an estimate is made of the concentration of the agent in the tested air.

To study the efficacy of passive monitors, NIOSH developed draft specifications for performance, protocols for testing, and criteria for evaluation (3). They tested passive formaldehyde monitors* now being widely marketed in the United States. These tests compared the performance of the passive monitors with results from independent testing using established traditional methods (NIOSH Physical and Chemical Analysis Methods 125 (4), and 354 (5)), and chromatographic analysis of 2, 4, dinitrophenyl hydrazine-coated silica gel tubes (6) (Table 1).

Testing of passive monitors, as marketed, consistently produced estimates of formaldehyde concentrations that were lower than those determined by the established sampling methods. Equilibration of the badges in an atmosphere of high humidity (92%) before exposure to the test atmosphere provided results comparable to results from traditional methods. This suggests that the discrepant performance of the passive monitors may be explained by a loss of moisture from the sorbent and/or operation in atmospheres with low humidity (based on laboratory tests, up to 40%).

Based on these findings, NIOSH concluded that the use of such badges, as marketed, cannot be relied on to produce consistently accurate measures of formaldehyde in the environment. NIOSH has notified the manufacturer of these findings. Reported by Methods Research Br, Div of Physical Sciences and Engineering, NIOSH, CDC.

Editorial Note

Editorial Note: Similar findings have been reported by other investigators (7), and NIOSH and CDC's Center for Environmental Health have received a number of telephone calls from state and local health agencies and from private individuals concerning the household use of these devices. Passive monitors for formaldehyde have been used to test for formaldehyde in the air of some 10,000 U.S. homes (8). Based on the findings reported above, the results of such tests should be interpreted with caution.


  1. Occupational Safety and Health Administration. Occupational and Safety Health Standards, General Industry. U.S. Department of Labor. 29 CFR 1910.1000.

  2. NIOSH current intelligence bulletin 34. Formaldehyde: evidence of carcinogenicity. U.S. Department of Health and Human Services publication (NIOSH) 81-111 (1981).

  3. Hull RD, Cassinelli ME. Tentative laboratory performance specifications, evaluation criteria and testing protocol for passive sampling. Draft NIOSH Technical Report (1982).

  4. National Institute for Occupational Safety and Health. NIOSH manual of analytical methods, Vol. I (2nd Ed.). U.S. Department of Health, Education, and Welfare publication (NIOSH) 77-157A, P&CAM 125 (1977).

  5. National Institute for Occupational Safety and Health. NIOSH manual of analytical methods, Vol. VII (2nd Ed.). U.S. Department of Health and Human Services publication (NIOSH) 82-100, P&CAM 354 (1981).

  6. Beasley RK, Hoffmann CE, Rueppel ML, Worley JW. Sampling of formaldehyde in air with coated solid sorbent and determination by high performance liquid chromatography. Anal Chem 1980;52:1110-4.

  7. Gammage RB, Hingerty BE, Womack DR, Hawthorne AR. Field intercomparison of formaldehyde monitors suitable for residential indoor measurements. Paper no. 19 presented at the 1983 American Industrial Hygiene Conference, Philadelphia, Pennsylvania, May 22-27, 1983.

  8. Anders LW, Shor RM. Formaldehyde concentrations measured in U.S. residences by diffusional samplers and impingers. Paper no. 20 presented at the 1983 American Industrial Hygiene Conference, Philadelphia, Pennsylvania, May 22-27, 1983.

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