Gas Detection Tubes
Gas detector tubes use well established technology to take 'grab samples' of suspected gases. The readings are generally referred to as 'qualitative', since the accuracy ranges +/- 20% of the actual value. The variety of gases available to be measured is extensive, and most of them are not readily detected by more common 4-gas meters. It is the ability to get an on the spot gas reading, with very little in the way of equipment or expense, that has made these colorimetric gas detection tubes so popular.
The RAE Systems by Honeywell brand uses a piston type pump to draw the target sample air through the tube. Simply break off both ends of the glass tubes and insert into the pump. In most cases, puling back just once on the plunger is all you need to do. An internal spring cycles a very specific amount of the air within the tube. Based on the concentration, a distinct stain appears as the crystals change color. The specific reading of the gas in question may then be read directly on the tube. Each tube is marked with gradations specific to the type of reading (i.e. % by volume, ppm, etc.).
Quality control is excellent, and the price is a bargain compared to other brands.