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  • Stephen Biss

Dental Work & Blowing into a Breathalyzer


After your dentist turns your mouth into a pin cushion, can you blow properly into an Intoxilyzer(R)? If your mouth is still numb, hours after a cavity is filled, can you blow properly?

Note: Using 150 solution for the cal. check.

There is a study by Pearson, G.J. and W.C. Keys "Local Dental Anaesthesia and Evidential Breath Testing: The Effect of Injection of Local Anaesthetic on Lip Seal" that states that 2 hours after injection every subject was able to provide satisfactory samples.(1)

As you can see from the above video, I had a lot of difficulty making a good seal around the mouthpiece at about 4 p.m.. My mouth had been injected between about 11:15 and 11:30 a.m.. The the cavities were replaced and fillings repaired up until about 12:45 p.m. Notice the air escaping from my upper lip. If this had been a real blow at a police station, I would have been accused of not making a tight seal around the mouthpiece. Even if the Intoxilyzer had accepted the sample, the breath tech would probably have considered it unacceptable and aborted the test.

Here is another video, of an attempt around 6 p.m. the same day. I was able to provide a sample that the instrument accepted. My mouth still felt strange. I used a different mouthpiece. I was able to make a better seal.

A few years ago I tried a similar experiment on an Intoxilyzer(R) 8000 about 2 hours after having a dental cavity repaired. I was trying to see if I got a false positive or interferent flag due to any specificity problem. I couldn't blow a test that the instrument would accept. My mouth wouldn't make a good enough seal.

I think a lot will depend on the model of the instrument and the particular instrument. Some Intoxilyzer(R) instruments are very easy to blow into and others are much more difficult. I think it has to do with the hardware and very much to do with the calibration of the flow. If it takes a lot of pressure ("Blow Harder") then it will be much more difficult to make a seal with your lips.

(1) Medicine Science and the Law, 29: 298-302, 189 digested in Wigmore on Alcohol.

Warning: These videos and these comments are not evidence. They cannot be used in Court. The author is not a scientist. This blog promotes discussion among lawyers and others involved in the justice system. Please retain an expert witness to give a proper opinion.


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