As a rule, every breathalyzer works from a chemical reaction. From the most portable ones to those carried in cases, any research will lead you to several types.
Regardless of which one you intend to buy, you should take into consideration the equipment's reliability. After all, Contran determines that the equipment must be approved by INMETRO, meeting the agency's requirements for precision and quality.
Thinking about the breathalyzer models, we can have it of two most common types: disposable or by fuel cell:
Disposable: These are single-use devices, where the air is inflated in bags intended for this purpose which, after being filled, are placed in a test tube with reagent. When the air is emptied, placing the tube in the bag outlet, the reagent changes colour, indicating the presence of alcohol.
By fuel cell: It is the most used by the Brazilian police. The breath containing ethyl alcohol generates a chemical reaction with the compound existing inside the equipment. The result is an electrical discharge and water in the form of steam. The equipment has sensors to measure the intensity of the discharge, which is presented in g/L of alveolar air.