For measuring the air concentration of chemicals including methanol.

These tubes are used to measure the average concentration of potentially harmful vapors in the air over a defined sample period. To use, the tube is connected to a small vacuum pump that draws air through the tube at a precise flow rate over a period of time. After the sample is taken, the tube is transported to a laboratory where they can remove the adsorbent material and perform analysis by solvent extraction and gas chromatography (GC) to determine the quantity of chemical collected, from which a time-weighted average (TWA) concentration can be calculated.