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A comparative study of commonly used instruments for assessment of indoor environmental quality.

Lawrence R; Martin S; Duling M; Calvert C; Hudnall J; Coffey C
American Industrial Hygiene Conference and Exposition, May 21-26, 2005, Anaheim, California. Fairfax, VA: American Industrial Hygiene Association, 2005 May; :68
Direct-reading instruments are used to characterize the indoor air environment. During field surveys these instruments can provide different results, even when placed side-by-side. A pilot study was developed to assess and evaluate the performance of direct-reading instruments to the manufacturers' specifications under varying environmental factors. This study consisted of three each of the most commonly used direct-reading instruments: TSI P-Traks, DustTraks, and Q-Traks, and GRIMMs with temperature and humidity probes. Testing was done for 18 days in two different environments, regulated air circulation (RAC) and minimal air circulation (MAC). Instruments were calibrated per the manufacturers' instructions and placed one foot apart in random order inside each environment. In the RAC environment, the location of the instruments was changed daily to offset any bias. Rotation of instruments was not required in the MAC environment. For each instrument type, the difference or percent difference was calculated between the instruments and compared to the manufacturers' specifications. For the MAC scenario, the Q-Traks provided CO2 (70.8%) and humidity (8.1%) values which were much greater than the manufacturer's specifications, (+/- 10.1% and +/- 3% respectively). The temperature difference (0.8%) was within TSI's specification (+/- 1.0 F). The total count difference from the GRIMMS (11.6%) was over five times higher than the manufacturer's specification (+/- 2%). Since the P-Traks, DustTraks, and GRIMMS (humidity and temperature) do not have published accuracy ranges, the National Institute for Occupational Safety and Health (NIOSH) method comparison accuracy criterion (+/- 25%) was used. Only the DustTrak results were greater than the NIOSH criterion, at 69.5%. Similar results were seen in the RAC environment. This study indicates that direct-reading instruments may not perform according to published specifications. This would greatly impact the characterization of indoor environmental air quality. NIOSH is currently conducting further research to determine the extent of this potential problem.
Environmental-factors; Air-monitoring; Air-quality; Air-quality-measurement; Air-quality-monitoring; Temperature-measurement; Temperature-effects; Humidity; Indoor-air-pollution; Indoor-environmental-quality
Publication Date
Document Type
Fiscal Year
NIOSH Division
Priority Area
Work Environment and Workforce: Indoor Environment
Source Name
American Industrial Hygiene Conference and Exposition, May 21-26, 2005, Anaheim, California
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division