A breathalyzer is a device that allows you to determine the concentration of alcoholic beverages by analyzing the air exhaled from a person's lungs. It is also known by the technical name “ethylometer”, due to the reactions that involve the ethyl alcohol present in the suspect's puff and a reagent.
All types of breathalyzers are based on chemical reactions, and the most common reagents are potassium dichromate and fuel cell. The difference between these two reagents is that the dichromate changes color in the presence of alcohol while the cell generates an electrical current.
The most used by police officers in Brazil is the Fuel Cell, the chemistry of this breathalyzer you can see below:
1. Expired alcohol reacts with the oxygen present in the device, this reaction takes place with the help of a catalyst;
2. Release of electrons, acetic acid and hydrogen ions occurs;
3. The electrons then pass through a conducting wire, generating electrical current. A chip present inside the device calculates the percentage and gives the concentration of alcohol in the blood. The more alcohol, the greater the electric current.
And there are no excuses for refusing to take the test, such as:
- Refuse to blow the straw because it is contaminated: it is disposable and has a valve that prevents the air from inside returning to your mouth;
- Say you can't blow? It takes 1.5 liters of air to make the measurement, it's the equivalent of a breath of five seconds.
What's more, it's no use trying to disguise your breath, chewing gum, drinking oil, etc. All these tricks won't stop you from losing your wallet and having your vehicle impounded.
Do not stop now... There's more after the advertising ;)
By Líria Alves
Graduated in Chemistry
Brazil School Team
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Would you like to reference this text in a school or academic work? Look:
SOUZA, Líria Alves de. "How the Breathalyzer Works"; Brazil School. Available in: https://brasilescola.uol.com.br/quimica/como-funciona-bafometro.htm. Accessed on June 28, 2021.
