# I'm an asthmatic with low "peak flow": should I be worried about the accuracy of breathalyser ? **URL:** \ **Category:** Factual Questions\ **Created:** [March 18, 2010, 8:04pm UTC](https://boards.straightdope.com/t/im-an-asthmatic-with-low-peak-flow-should-i-be-worried-about-the-accuracy-of-breathalyser/532929 "2010-03-18T20:04:49Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![griffin1977](https://avatars.discourse-cdn.com/v4/letter/g/977dab/32.png) [@griffin1977](https://boards.straightdope.com/u/griffin1977)\ **Post date:** [March 18, 2010, 8:04pm UTC](https://boards.straightdope.com/t/im-an-asthmatic-with-low-peak-flow-should-i-be-worried-about-the-accuracy-of-breathalyser/532929/1 "2010-03-18T20:04:49Z")
So something occurred to me while be followed by a cop on the way back from the pub the other night (turns out I was never pulled over, but it got me thinking). I was well under the limit, but the thing is I’ve had asthma since childhood. Its well controlled but my [“peak flow”](http://www.patient.co.uk/health/Asthma-Peak-Flow-Meter.htm) has always been far lower than it should be for my weight (I’m 6ft and well over 200 pounds). Should be worried that a breathalyzer would be significantly inaccurate for me ? It seems reasonable as its based on the amount of alcohol released in the air in my lungs (less air==higher concentration of alcohol ?). This a purely biological question, not a legal one, and I’m certainly not interested in getting out of a legitmate DUI bust, but what is the science of this ? Though a follow up question (this IS a legal one), in California do I have the right demand a blood test ? And how unpleasant can the cops make my life if I demand one ? ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [March 19, 2010, 5:12am UTC](https://boards.straightdope.com/t/im-an-asthmatic-with-low-peak-flow-should-i-be-worried-about-the-accuracy-of-breathalyser/532929/2 "2010-03-19T05:12:27Z")
I’m going to sorta bump this by offering my opinion. I would think that breathing out less air means you would necessarily breathe out less alcohol, and thus the two things would mostly cancel out. A bigger problem might be if your inhalant medication caused a false positive. Many people claim that this happens. Another might be what happened in [this case](http://www.freerepublic.com/focus/f-news/1550354/posts), where the person couldn’t blow hard enough for the breathalyzer to get a reading. ---
**Author:** ![Askance](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/askance/32/8281_2.png) [@Askance](https://boards.straightdope.com/u/Askance)\ **Post date:** [March 19, 2010, 5:14am UTC](https://boards.straightdope.com/t/im-an-asthmatic-with-low-peak-flow-should-i-be-worried-about-the-accuracy-of-breathalyser/532929/3 "2010-03-19T05:14:46Z")
I’m with **BigT** , I don’t believe this would change the concentration of alcohol in your breath. But in most if not all jurisdictions I’ve heard of, you are entitled to demand a blood test, which is after all what the laws are based on - the breath reading is just an indication, not a basis for indictment itself. ---
**Author:** ![griffin1977](https://avatars.discourse-cdn.com/v4/letter/g/977dab/32.png) [@griffin1977](https://boards.straightdope.com/u/griffin1977)\ **Post date:** [March 20, 2010, 12:32am UTC](https://boards.straightdope.com/t/im-an-asthmatic-with-low-peak-flow-should-i-be-worried-about-the-accuracy-of-breathalyser/532929/4 "2010-03-20T00:32:27Z")
> [@Askance](#): > > I’m with **BigT** , I don’t believe this would change the concentration of alcohol in your breath. But in most if not all jurisdictions I’ve heard of, you are entitled to demand a blood test, which is after all what the laws are based on - the breath reading is just an indication, not a basis for indictment itself. Though in the example **BigT** quotes above someone was arrested for refusing a test as she had asthma, and so could not prove a large enough sample. If you have the right to a blood test why wasn’t one administered ? > [@](#): > > However, the Breathalyzer machine at the jail printed out a ticket saying the sample was invalid. The deputy told Upchurch she was not blowing hard enough into the machine, and she told him she had asthma. She later presented in court a letter from her physician confirming she had the breathing disorder. > > After a second test with the same result, officers arrested the woman, and prosecutors charged her with operating a vehicle while intoxicated and endangering another person.