Those who dont know what is the breathalyzer , it is deice used to check the alcohol level in blood.
well Breathalyzer wont literally check the blood but it takes input as the breathe from testing individual.
when the person is asked to blow into the breathalyzer it checks the quantity of alcohol observed in blown air. yess when you drink your mouth and lungs,stomach has that influence of alcohol.
Robert Frank Borkenstein professor at the university of Indiana is the one who developed it .
How they measure
BAC(blood alcohol consumption) is the most commonly used term to measure how much alcohol a person took.
In India ,the BAC legal limit is 0.03% that is 30 micro liters in 100 ml blood.
There are many technologies came to check the alcohol levels in blood but the most commonly used by police is table-top breathalyzers.
There are some myths that having breathe mints and onions will escapes you from detecting but ,they wont work .if you want to try you can ,but i dont recommend cause you may end up getting caught.
source : breathalyzer.net