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Estimation of required monitoring time for obtaining validation data in enclosed spaces.

Authors
Lee-EG; Feigley-CE; Hussey-JA; Slaven-JE
Source
J Environ Monit 2008 Oct; 10(11):1350-1356
NIOSHTIC No.
20034752
Abstract
Methods for estimating airborne contaminant concentrations at specific locations within enclosed spaces, such as mathematical models and computational fluid dynamics (CFD), often are validated against directly measured concentrations. However, concentration variation with time introduces uncertainty into the measured concentration. Failure to determine monitoring time requirements can lead to errors in quantifying representative concentrations, which are likely to be attributed to errors in the method being validated. In the current study, to obtain the representative concentrations at multiple locations with a direct reading instrument, we used the standard deviation ratio (SDR) method to determine the required minimum monitoring time within a specified precision limit. To demonstrate the use of the SDR approach in constructing precision confidence intervals, tracer gas concentrations at nine sampling locations in an experimental room were measured to obtain population parameters. Three flow rates of 0.9, 3.3 and 5.5 m3 min-1 were employed and contaminant concentrations were measured using a photoionization analyser. Monitoring time requirements varied substantially with location within the room and were strongly dependent upon the flow rate of air through the room. The proposed method would be very useful for industrial hygienists and indoor air researchers who sometimes need to obtain several hundred measured concentrations for validation purposes or to perform tests under repeatable conditions in enclosed spaces. This study also showed that the proposed method can be used to devise efficient indoor monitoring strategies.
Keywords
Aerosol-particles; Indoor-environmental-quality; Confined-spaces; Statistical-analysis; Statistical-quality-control; Mathematical-models; Measurement-equipment; Monitoring-systems; Air-sampling-techniques; Air-quality-measurement; Airborne-particles
Contact
Eun Gyung Lee, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Exposure Assesment Branch, Health Effects Laboratory Division, 1095 Willowdale Road, Morgantown, WV 26505
CODEN
JEMOFW
Publication Date
20081001
Document Type
Journal Article
Email Address
dtq5@cdc.gov
Funding Type
Grant
Fiscal Year
2009
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-007626
Issue of Publication
11
ISSN
1464-0325
NIOSH Division
HELD
Source Name
Journal of Environmental Monitoring
State
WV; SC
Performing Organization
University of South Carolina at Columbia, Columbia, South Carolina
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