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PB2004104099

Publication Date	2003
Page Count	26
Abstract	In outdoor engineering control studies, measured analytic concentration levels change as environmental conditions change. Since the effectiveness of an engineering control varies with environmental conditions, comparisons of measurements taken with engineering controls operating versus those taken in an uncontrolled environment should adjust for these changes. However, environmental parameters are difficult to estimate. In this work, models based on factor analysis are used to account for the effect of environmental variables. These models also describe the phenomenon that greater control efficiency tends to occur at the highest levels of the uncontrolled environment. The approach is combined with the randomized pair (uncontrolled environment determination, engineering control determination) approach that is often used in these studies. Also investigated are the benefits of taking samples at different locations and of different analytes.
Keywords	Engineering controls Environmental variations Randomized pairs Models Outdoors Derivations Analyte concentrations Environmental conditions Changes Comparisons Measurements Factor analysis Uncontrolled environments
Source Agency	National Institute for Occupational Safety and Health
Corporate Authors	National Inst. for Occupational Safety and Health, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200414

Adusting for the Effect of Environmental Variability in Outdoor Engineering Control Studies; Detailed Derivations.

Adusting for the Effect of Environmental Variability in Outdoor Engineering Control Studies; Detailed Derivations.
PB2004104099

Publication Date	2003
Page Count	26
Abstract	In outdoor engineering control studies, measured analytic concentration levels change as environmental conditions change. Since the effectiveness of an engineering control varies with environmental conditions, comparisons of measurements taken with engineering controls operating versus those taken in an uncontrolled environment should adjust for these changes. However, environmental parameters are difficult to estimate. In this work, models based on factor analysis are used to account for the effect of environmental variables. These models also describe the phenomenon that greater control efficiency tends to occur at the highest levels of the uncontrolled environment. The approach is combined with the randomized pair (uncontrolled environment determination, engineering control determination) approach that is often used in these studies. Also investigated are the benefits of taking samples at different locations and of different analytes.
Keywords	Engineering controls Environmental variations Randomized pairs Models Outdoors Derivations Analyte concentrations Environmental conditions Changes Comparisons Measurements Factor analysis Uncontrolled environments
Source Agency	National Institute for Occupational Safety and Health
Corporate Authors	National Inst. for Occupational Safety and Health, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200414