For monitoring atmospheric gasses
The Draeger Diffusion Tubes are direct reading, scaled tubes that can be used for determining time weighted average concentrations. The tubes work by passive gaseous diffusion and can be used over a period of 8 hours or longer in some cases.
Designed as a personal monitor, the diffusion tubes also can be used for area monitoring. The diffusion tubes are used with an ultralight plastic reusable holder which attached to clothing and protects the tube during use. The time weighted average can be calculated at any time during the measurement by simply dividing the length of the tube reading by the elapsed sampling time (in hours).