I keep getting 0 readings on my breathalyser

The typical situation is - you've had a beer or two, waited 20 minutes, then test yourself and get 0. 

This can be normal (we'll explain more below) and so we recommend testing yourself at intervals (e.g. 30 mins, 60 mins, 90 mins, 2 hrs, etc. and morning after) as alcohol may take time to be absorbed into your bloodstream. 

Why am I getting a 0 reading after I've had a pint / glass of alcohol?

  • Alcohol level too low
    Put simply - at very low levels of alcohol (which are a long way below the drink driving limits) most breathalysers (including full Police issue) will struggle to pick up a positive reading when the breath sample has very low alcohol content. This is why they will often give a 0 reading. Additionally, some semiconductor breathalysers are optimised to read better at moderate to higher levels.
  • Liver processes alcohol quickly
    In addition, unless you have been drinking very heavily for some considerable time and have had a very limited amount of sleep, most healthy livers will process the alcohol far more quickly than most people expect.
  • Depends on time alcohol takes to reach bloodstream
    When you stop drinking your level of intoxication may stay constant or if you have been drinking heavily it could even increase for around 2 hours afterwards. This is because of the time it takes for alcohol to reach the bloodstream from the time you actually had the drink.
  • Food intake slows absorption of alcohol 
    If you have eaten food before consuming alcohol, this can also increase the time it takes alcohol to reach your bloodstream, because the release of alcohol into the bloodstream can be slowed by being absorbed by the food in the stomach.

This is the reason why we do not recommend the use of a breathalyser just after you've finishing drinking because there are so many factors that can influence the reading. 

It's best to test at multiple intervals throughout the night, and also the morning after.

How long do I need to wait after consuming alcohol, eating or smoking to perform a breath test?

You should wait at least 20 to 30 minutes after eating, drinking or smoking before performing a breath test. On some occasions, if you have drunk heavily, very quickly, it is advisable to wait up to 90 minutes before performing a breath test to allow the alcohol you have drunk to get from the stomach and into your blood stream. 


I keep getting different readings on my breathalyser:

There are many factors that affect the amount of alcohol in your breath and your reading:.

  • Alcohol in your mouth - Alcohol in your mouth will dramatically increase the reading a breathalyser gives, for this reason we always advise waiting 15-30 minutes from your last drink and rinsing your mouth with water before taking a test.  Some medicines and mouth washes have alcohol that can be detected by your breathalyser.  Additionally semi-conductor breathalysers may detect the presence of certain sugar alcohols which may cause higher than expected readings.
  • Alcohol or moisture in the mouthpiece - It is always recommended to use a new or clean mouth piece for each test.  Residual alcohol or moisture in the mouthpiece from previous tests can effect the readings from subsequent tests.
  • Moisture in the sensor - Excessive moisture in the sensor can effect the reading produced in the short term and in extreme cases can damage the sensor.  Moisture can get into the sensor inadvertently by accidentally spitting into the unit while you blow, typically semi-conductor units are more susceptible to this issue.  Always ensure your mouth is clean and free from excess saliva before you blow.  Excessive use in a short period can also cause moisture to build up inside the sensor, fuel cell sensors are better designed to handle multiple tests.  Industrial units with larger fuel cells are generally able to handle many tests without suffering a loss of accuracy.
  • Body type, Metabolism and Gender - The way each persons body reacts to and processes alcohol is different.  Your body type, metabolism, and gender can effect how quickly your body absorbs and burns alcohol.  Two people drinking the same drinks at the same time can have greatly different blood and breath alcohol levels.

Always remember that after heavy, rapid drink consumption, your blood and breath alcohol levels can continue to rise for an hour or longer after your last drink.