Kitchen Science Experiments

Can you beat the Breathalyzer

Sun, 17th Dec 2006

Part of the show The Christmas Q & A Show

What you Need

  • An Aussie Backpacker
  • Some alcohol
  • A breathalyser
  • A friendly policeman

What to do

  1.   Feed some alcohol to the backpacker. You don't want to make her sick, but you do want her to get a reading on the breathalyser. About four units should do the trick.
  2.   Wait. Alcohol takes time to absorb into the bloodstream. About half an hour is a good amount of time.
  3. Breathalyse. The backpacker has to breathe into the machine until it beeps.
    Try various ways to get around the test. Mints to mask your alcohol breath, and mouthwash are good experiments to try.

What may happen


The lungs exchange oxygen from the air into the bloodstream, as well as alcohol from the bloodstream into the air in the lungs. The alcohol that is absorbed from the blood into the lungs is then breathed out into the machine.

The breathalyser has a fuel cell in it. In a car, a fuel cell uses hydrogen and turns that into an electrical current. In the breathalyser, there are a couple of platinum electrodes that use the alcohol in the machine to create the electrical curent. The level of the current indicates the level of the alcohol in the machine, which indicates the level of alcohol in the blood.

Chewing gum has no effect whatsoever on the blood alcohol level and as a result the breathalyser result is no different.
Mouthwash however had a major effect on the breathalyser, because alcohol is a key ingredient. The breathalyser is supposed to read lung alcohol only however because our backpacker swilled the mouthwash immediately before taking the test the machine did erroneously measure her mouth alcohol level and as a result the breathalyser reading was sky high. Not a good way to try and trick the police!

Why does it happen?

Multimedia

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