The breath test consists of a measurement of the alcohol in an appropriate sample of breath: that is, you blow on the device and the device measures the amount of alcohol in your breath.
Actually the explanation is not entirely accurate: the breathalyzer is not interested in your breath, but the air from the deepest part of your lungs: from the pulmonary alveoli.
Hence, the traffic agent forces you to inspire with force and to literally expel "every last drop of air from your lungs". The apparatus usually takes as sample only the final part of that exhalation of air.
Why the alveolar air?
The pulmonary alveoli are the last recesses of our lungs. It is precisely where the gas exchange takes place between our circulatory system and the outside: through the alveoli we release the CO2 and absorb the O2.
Precisely for this reason, it is accepted that the alveolar air is in equilibrium with the blood, so that the gases of the blood are in equilibrium with the alveolar air.
What does this mean? Well, Henry's Law is fulfilled.
Henry's Law
Henry's law says that, at a constant temperature, the concentration of gas dissolved in liquid is in proportion to the concentration in the air directly above the liquid.
That is, imagine that we mix alcohol and water in a glass: Henry's law says that part of the alcohol comes out of the water and into the air. In addition, the more alcohol we have in the water, the more amount will go into the air.
Well the same goes for blood: if our blood contains alcohol by the cups, the alveolar air also contains alcohol. And the more drinks we have taken, the more alcohol our alveolar air will have.
Cheat the breathalyzer?
As the air that analyzes the breathalyzer is not that of our mouth but that of our alveoli, forget about trying to deceive the apparatus by masking the breath: neither chewing gum, nor candy, nor coins, nor grass, ... none of that works.
Here we discuss some other ways (in addition to those already discussed) in which it is intended to elude the device:
Lick coffee beans. It has no foundation.
A spoonful of oil. It has no foundation.
Almax, ibuprofen and other medications. It has no foundation.
Eat. Eating alcohol takes longer to take effect because it takes longer to spread throughout the body.
Tacos with lots of onion, cilantro and salsa. False, just like before.
Aspirate instead of blowing. The agent will notice immediately.
Toothpaste. It does not have any use either.
Drinking water. It has no basis, because it does not help to dilute alcohol.
Barf. The only thing that is achieved is to eliminate alcohol from the stomach, but not the one in the blood.
I do not know about you, but they remind me of the poor natives who sacrificed a virgin by throwing her to the volcano to appease her fury. Useless, and always based on superstitions without foundation or knowledge.
Is the breathalyzer 100% reliable?
As you will understand there have been numerous tests to see if the breathalyzers are reliable. It has been found that in general yes, they are quite reliable devices, except in some cases:
Physical exercise or very rapid breathing can decrease results: In one study, the test results in individuals decreased by 11% to 14% after running by a ladder degree and by 22% to 25% after running by two degrees of stairs. In another study, individuals who did demanding rapid breathing exercises had results decreased by 15%.
On the other hand, body temperature also affects the rate: at higher temperatures, the device detects a higher rate of alcohol. It is logical: the higher the temperature, the higher the volatility of the alcohol and therefore more alcohol goes into the alveoli, resulting in a higher result.
Mouthwash liquids increase the rate initially, since they contain alcohol.
So for now, as far as we know, the only way to not test positive in BAC is to NOT DRINK BEFORE DRIVING.
If after all this you want to continue investigating how to cheat the breathalyzer, go ahead, maybe you find how to cheat, but can you deceive Death if it surprises you in the next curve?