Gaseous contaminant dosimeter with diffusive material for regulating mass uptake

A gaseous contaminant dosimeter apparatus for determining the amount of gaseous contaminants in a gas mixture and whereby the gas mixture is air and the selected gaseous contaminants are one of the group of benzene, alkyl benzenes, alkanes, alkenes, alkynes, chlorinated hydrocarbons or other organic compounds or combinations thereof, the apparatus comprising:

• a container having an opening formed therein, and defining an internal portion;
• a diffusing material mounted on the container and disposed in fluid impeding relation in the opening thereby isolating the internal portion of the container from the gas mixture, the diffusing material including at least one microporous membrane wherein the passage of said gaseous contaminants through the microporous membrane is substantially by Knudsen Regime diffusion;
• and
• a collection medium is received in the internal portion of the container and includes activated charcoal, silica gel or other material which adsorbs, absorbs or reacts with the aforementioned selected gaseous contaminants, the collection medium being compatible with measurement methods specific and quantitative for the measurement of said gaseous contaminants so collected.

A method of determining the concentration of a selected gas contaminant in a gas mixture during a predetermined time, comprising:

• providing a container defining a chamber and having an opening formed therein;
• forming a diffusion barrier by laminating opposite sides of a macroporous support member with an individual microporous membrane having an effective pore size of at least 0.02 micrometers, the diffusion barrier operable to regulate the mass transfer of the selected gaseous contaminant by Knudsen Regime diffusion;
• positioning the diffusion barrier in fluid impeding relation in the opening;
• depositing a collection medium in the chamber which is adapted to react with the selected gaseous contaminants, the collection medium being compatible with measuring methods specific and quantitative for the measurement of said gaseous contaminant;
• and
• exposing the diffusion barrier to the gas mixture for a predetermined period of time thereby permitting the collection medium to adsorb, absorb or react with the gaseous contaminant which diffuses through the diffusion barrier.