Breathalyser Terminology & Abbreviations

Breathalyser terminology


  • BAC= Blood alcohol concentration
  • Commonly displayed as a percentage %BAC or mg/100ml. 
  • Few breathalyzers on sale in UK display in BAC 


  • BRAC= Breath alcohol concentration.
  • Most newer models of breathalyzer display BRAC in mg/L (milligram per Litre)

Breathalyser Accuracy

  • Accuracy= the selectivity achievable when the breathalyser sensor is correctly calibrated.
  • This is often displayed as the variation accepted in %BAC ie +/- 0.01%BAC means the breathalyzer will display with an accuracy of + or - 0.01 on the display 0.05 the breathalyser may display a variance of 0.04 to 0.06 on a series of 3 tests done in succession.
  • A greater variance would indicate a possible loss of calibration, sensor failure, evaporating mouth alcohol or poor breath sampling technique.

Breathalyser Calibration

  • Calibration = the service which sets the reading accuracy of the sensor.
  • Breathalysers which do not have interchangeable sensor modules will need to be sent for service periodically for a calibration service to maintain their accuracy.

Chemical Breathalyser

chemical breathalyser is a single-use disposable breathalyser kit which you blow through. A chemical reaction takes place between the alcohol in your breath and the crystals in the breathalyser and produces a colour change. The colour corresponds to a particular level of alcohol in the blood. They come with a chart so that you can interpret the results. They are highly accurate around 98%, and are a very good first line alcohol screening tool. They have an expiry date after which they should be discarded.

Digital Breathalyser

digital breathalyser is an electronic breathalyser rather than a chemical breathalyser. It contains a sensor that detects alcohol in the breath sample. The accuracy of the breathalyser tends to follow price with the more expensive models having higher accuracy levels. All the models that we stock are highly accurate provided that they are used and stored correctly, and re-calibrated correctly.

Re-calibration of digital breathalysers

A digital breathalyser will need regular re-calibration to make sure that it is retaining its accuracy. For the models with a semiconductor sensor, this usually means simply purchasing a new breathalyser sensor about every 6 months, and fitting it yourself. Some of the newer fuel cell sensor models also have a sensor which you can change easily yourself. Models such as the Draeger 6820 breathalyser will require returning to a calibration centre.