Protective Ensemble Testing Using Passive Sampling Devices
Authors: Kuhlman MR , Coutant RW , Fritch WM 
Published: February 2009

The protection afforded the wearer of individual protective equipment is determined by the amount of challenge penetration through the materials used in the equipment and the leakage which occurs through the various suit closures. In this study, a passive sampling technique was used to measure quantitatively the amount of leakage into protective ensembles designed for use in a hazardous chemical environment. The technique involves fastening several passive sampling devices (PSDs) to subjects who subsequently don the protective ensembles in a 17-m3 test chamber. A constant concentration of 10-ppm isoamyl acetate is maintained in the chamber throughout a one-hour exposure period during which the subjects perform a set of movements designed to stress the suit seals in a manner simulating actual use conditions. Following the exposure, the samplers are retrieved and the mass of isoamyl acetate collected by each is measured. This measurement is then used to assess the protection provided by the ensemble for each PSD location.

The principle of operation of the PSDs is molecular diffusion of the challenge vapor into the pores of the sorbent material used in the PSD. These devices are characterized by an effective sampling rate which depends upon the PSD geometry and the diffusivity of the vapor being sampled. This sampling rate does not require that air be actively pulled through the PSDs, so no disturbance of the existing air circulation is required. These samplers provide a time-integrated measurement of the dosage experienced at the sampling location. The Tenax GC sorbent used in the samplers employed in this study is not adversely affected by the high humidity in the ensemble interior and permits greater sensitivity than other sorbents used in such devices.

The reproducibility of the PSDs is typically ±20% under controlled conditions. The scatter is considerably greater, however, in the test results reported here. The analysis of the vapor collected by the PSDs is performed by thermally desorbing the adsorbed vapors and flushing them onto a gas chromatographic column. The sensitivity of the analytical technique is sufficient for measurement of collected masses of 30 ng, but reproducibility of the analysis of blank PSDs placed the practical lower detection limit at 100 ng. This permits measurements of protection factors from 1 to 1000, for the conditions of these tests.

The testing produced measurements of the protection factors at a variety of body locations for different size ensembles and for several levels of wearer activity. Three subjects and a mannequin were exposed to the vapor challenge in a matrix of 30 tests which resulted in the collection of 345 samples and analytical blanks. The overall data capture rate for this study was 95%. The results indicate which seals are most subject to leakage and demonstrate the influence of wearer movement on the protection factors provided by the ensemble.

This technique is applicable to the testing of other protective clothing and is adaptable to the level of sensitivity required of the testing.