How does a breathalyser work?

  • 4 Replies
  • 4257 Views

0 Members and 1 Guest are viewing this topic.

*

Offline chris

  • Neilep Level Member
  • ******
  • 5424
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
How does a breathalyser work?
« on: 08/10/2007 11:10:56 »
It's the 40th anniversary of the breathalyser this week. But how does a breathalyser work? In the old days it involved some crystals that changed colour but now it seems to be all done electronically. But how?

Chris
I never forget a face, but in your case I'll make an exception - Groucho Marx

*

paul.fr

  • Guest
How does a breathalyser work?
« Reply #1 on: 08/10/2007 15:41:23 »
Something to do with electrodes measuring current...i think Dave did a kitchen science with a  breathalyser and some Australian backpacker if i remember correctly.

*

Offline eric l

  • Hero Member
  • *****
  • 514
    • View Profile
How does a breathalyser work?
« Reply #2 on: 08/10/2007 17:25:43 »
Found this :  http://science.howstuffworks.com/breathalyzer4.htm

In this article, "breathalyzer" is used for the devices based on colour change, while the electronic devices would be classified as "intoxilzer".  It seems these intoxilyzers are based on IR absorption measurement.

The interesting point is the ratio between alcohol in the exhaled air as compared to the alcohol in the blood.  If that is less constant than what is mentioned in that paper, the validity of data from breathlyzers and intoxilyzers would be doubtful.
"Wonder is no wonder" (Simon Stevin 1548-1620)

*

another_someone

  • Guest
How does a breathalyser work?
« Reply #3 on: 08/10/2007 17:35:19 »
I am not sure if it is mandatory, or merely an option, but I believe a positive breathalyser test may, or must, be followed up with a blood test.

*

Offline eric l

  • Hero Member
  • *****
  • 514
    • View Profile
How does a breathalyser work?
« Reply #4 on: 09/10/2007 08:40:21 »
I am not sure if it is mandatory, or merely an option, but I believe a positive breathalyser test may, or must, be followed up with a blood test.
As far as I know, in Belgium the bloodtest is still mandatory in case of accidents, not with routine roadside controls.  Your driving licence can be suspended for a number of hours based on breath test alone; I am not quite sure if a blood test is not needed if your driving licence is to be taken away for a longer time.
"Wonder is no wonder" (Simon Stevin 1548-1620)