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Drink Driving Information

Drink Driving Prescribed Limits

  • Breath – 35 microgrammes of alcohol in 100 millilitres of breath

  • Blood – 80 milligrammes of alcohol in 100 millilitres of blood

  • Urine – 107 milligrammes of alcohol in 100 millilitres of urine

Converting Readings For Breath/Blood/Urine

  • To convert breath alcohol reading to its blood alcohol equivalent multiply by 2.3 (and roundup to the nearest whole number
  • To convert breath alcohol reading to its urine alcohol equivalent multiply by 3.06

Rates of Alcohol Metabolism

The rate at which alcohol is metabolised (the rate at which alcohol in the body will be removed) will vary from person to person depending upon a number of factors including a persons sex, tolerance to alcohol, the consumption of food and also the effects of certain medications.

The average rate of alcohol metabolism is accepted to be 6.5 microgrammes per 100ml of breath per hour. However, some studies have suggested that this may be as high as 8-9 mg and for some as high as 15mg.

How long does it take alcohol to be absorbed

It is generally accepted that after the consumption of alcohol it will take between 15 and 90 minutes for the peak concentration in blood to be reached and in most cases 30 minutes.

Can I calculate what my breath alcohol reading should have been following my recollected consumption?

Yes. There are a number of websites which provide this facility. Please see the links below which provide automated calculations: