The tester consists of a small (70 mm) glass tube containing yellow chemicals, which turn green in the presence of alcohol. The length of the green colour change is in proportion to the amount of alcohol. The tube has an arrow indicating the direction in which the breath must be passed and also a red calibration line indicating the legal driving limit.
Inside the tube on either side of the yellow chemicals is a filling of white crystals, which protect the chemicals against moisture and give the product a shelf life of 2 years. This storage Silica Gel is harmless and non- toxic.
A plastic snap-off end cap closes both ends of the tube. A plastic bag containing a neck valve, which measures the volume of breath passed through the tester, accompanies each tester.
The plug of chemicals is located in the tube by means of two resistant sieves.
The size of the plug, the nature of the particles and the chemical impregnation are designed to allow the breath to pass through at the correct rate for any alcohol in the breath to react with the chemicals and change the colour from a yellow to green.
The measuring bag is a critical part of the system as it measures the amount of the breath, which is passed through the tester. The volume is the basis on which the calibration is done.
The US Consumer Product Safety Commission has determined that the Redline product does not indicate any potential hazard or toxicity that would require any specific labelling.