Avoiding police manipulation of breath tests

Police manipulate breath testing devices (breath alcohol machine) by controlling the way people blow into them. Usually, police officers tell a person taking an alcohol breath test to take a deep breath and to blow into the machine as long as possible. During the test the officers will encourage this by telling the test subject to “blow, blow, blow” until the person runs out of breath. The alcohol breath test results then produce a falsely high number.

The blow alcohol tester machines are designed to estimate your blood alcohol content or BAC by measuring your breath alcohol. To do this the machines must use certain assumptions about your temperature, blood particulate levels, and several other factors.

By far the most important factor is temperature. Henry’s Law says that the concentration of a substance contained in the gas found in the headspace over a liquid is directly proportional to the temperature at the point of exchange. In breath testing terms this means that the warmer your lungs are, the more alcohol will be in your breath, regardless of the concentration of alcohol in your blood.

When you hold your breath before breathing into the breath test machine your lungs warm up. The amount of alcohol in your breath increases. Then, when you blow all of your breath into the machine, you blow the very warmest breath at the end, and that is what is tested. These procedures create a falsely high result.

The breath test machine (with a couple of exceptions where the machine measures breath temperature) assumes that your breath temperature is 34°C. That is about 92.8°F. When you hold your breath before blowing into the machine you can warm it up to 37°C (about 98.6°F) and if you have a fever it will go even higher.

Maine Breath Test AdviceFor every degree centigrade that your breath is over 34°C the breath test result increases somewhere between 6.5% and 8.5%. So if you hold your breath and the temperature goes up to 37°C you might increase the breath test result by 25.5%. This means that if your blood-alcohol level is .07% and you hold your breath, bringing your breath temperature up to 37°C, you will blow .08% or .09%. Although you’re really under the limit you will read as being over the limit.

How to Avoid Breathalyzer False Readings

You can learn how to prevent higher alcohol breath results. This involves controlling your breath temperature and breathing.

The first thing you need to do is not let your breath temperature get too high. This means you should breathe deeply and quickly, in and out 3 or 4 times, before you blow. Don’t hold your breath. When you take that last breath don’t take a deep breath, just take a normal breath and blow normally – not as hard as you can. And then blow immediately into the police breath machine without holding your breath. This will keep your breath temperature down around 34°C.

The second thing you need to do is control how much breath goes into the machine. The machine does not require that you breathe in all the breath possible. Most machines only require about 1.1 L of breath. The average person can blow 4 or 5 L of breath if they take a good, deep breath.

Remember that the breath at the end of your breathing cycle is warmer than the breath of the beginning. So once you start to blow, blow normally–not too hard–and blow for only 6 seconds. Count to 6, by 1000’s in your head. Then stop blowing. If you blow a steady stream into the machine you will have blown enough air.

The result should be anywhere from 25% to 50% less than it would be if you held your breath and blew as long and as hard as you can.

Warning: You need to be aware that if you refuse a breath test and you are convicted of DUI in Maine you will face harsh suspension penalties.

Penalties for Refusal

  • 1st refusal – 275-day driver’s license suspension
  • 2nd refusal within 10 years – 2 year driver’s license suspension
  • 3rd refusal within 10 years – 4 year driver’s license suspension
  • 4th refusal within 10 years -6 year driver’s license suspension

Driver under 21

  • 1st refusal – 18 month driver’s license suspension
  • 2nd refusal – 30 month driver’s license suspension

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