Permeation

Protective clothing worn by personnel working with liquid and gaseous chemicals is designed to reduce direct skin contact. Chemical liquids and gases can pass through the clothing barrier by permeation, i.e. transport at a molecular level via sorption, diffusion, and desorption.

TPACC evaluates material performance using the test cell and procedures indicated in the ASTM F 739 method. When mounted in the test cell, specimens partition the challenge chemical from the collection medium used to capture permeation of the challenge. The collection medium is analyzed for content of the challenge chemical with initial detection time reported along with time permeation rate reaches a specified level.

Measurement of permeation resistance is also indicated by the National Fire Protection Association (NFPA) 1994 Standard on Protective Ensembles for First Responders to CBRN Terrorism Incidents. TPACC measures permeation resistance for the liquid and gaseous toxic industrial chemicals (TICs) indicated: dimethyl sulfate, acrylonitrile, acrolein and ammonia, chlorine, respectively.

The NFPA procedure requires the test material be exposed to the challenge TIC for no less than a one hour. Only the CBRN barrier material of a garment system is evaluated for permeation resistance. Swatches of barrier material are first conditioned using specified flex and abrasion protocols. Cumulative permeation of the challenge TIC during the 60 minutes test is quantified by analytical procedures selected as appropriate for the particular agent. Ammonia, chlorine and dimethyl sulfate are analyzed by ion chromatography, while permeation of acrolein and acrylonitrile utilize gas chromatography. Contact us to request evaluation of permeation resistance using non-standard chemicals or for breakthrough testing.