A workplace protection factor (WPF) study was conducted with a half-mask ai
r-purifying respirator during fiber glass boat production. Styrene was the
measured analyte, and the geometric mean WPF found was 39.7. Analytical det
ection limits, sample contamination, and pulmonary elimination from previou
s exposures or from skin absorption were identified as important considerat
ions that can bias the WPFs measured. There were significant differences in
the mean concentrations found inside the respirator when analyzed by time
period. An increase in the concentration found inside the facepiece cavity
and a decrease in the WPF over time was found for people with three or four
measurements. This indicates either a change in performance of the respira
tor over time or a bias from low-revel exposures during the day or skin abs
orption.