Breath alcohol testing

Various devices are used privately and by the police to measure breath alcohol. These devices are calibrated periodically using high precision specialty gases mixtures containing ethanol.

Breath Alcohol Content (BAC)

Police forces across Australia enforce legal limits of breath alcohol to preserve safe driving conditions for all road users. While there are minor variations between states and territories, a level of 0.05 grams (50 milligrams) of alcohol in every 100 millilitres (ml) of blood generally applies for experienced car drivers.

In some states there is a graduated increase in fines for BAC levels rising from 0.05 to 0.15 grams of alcohol per 100 ml of blood. For example in Western Australia fines range from $400 infringement with a $500 maximum court penalty and 3 demerit points, up to $3500 court penalty and 30 months disqualification. For repeat offenders at the higher limit level, the court penalty may be a custodial prison sentence of up to 9 months for second offences and 18 months for third offences.

Drivers in sensitive categories are subject to a lower limit, which is referred to as a Zero BAC limit. In practice, this means less than 0.02 grams (20 milligrams) of alcohol in every 100 millilitres of blood.

As an example, in New South Wales the Zero BAC limit applies to:

  • Drivers of heavy vehicles of "gross vehicle mass" greater than 13.9 tonnes. Many of the Coregas delivery fleet fall into this vehicle weight category
  • Drivers of vehicles carrying dangerous goods, for example the Coregas cylinder and bulk liquid tanker drivers fall into this category
  • Drivers of public transport vehicles, such as bus drivers and taxis

Evidential BAC analysers

With the stakes for drink driving being so high, it is essential that breath alcohol measurements are made accurately. For such measurements the equipment is referred to as evidential breath analysers. These should comply with NMI R 126:2000 and require robust calibration and testing according to the procedures laid out in NMI R 126, the Pattern Approval Specifications for Evidential Breath Analysers. For these calibration tests a range of calibration gas mixtures containing between 25 and 220 ppm of ethanol in air may be used; these are referred to as "dry gases". Alternatively air or a gas mixture of 80% nitrogen, 15% oxygen and 5% carbon dioxide to simulate exhaled breath may be bubbled through an alcohol in water solution to create the required calibration or test gas mixture.

Private use BAC analysers

In addition to evidential breath analysers used by the police, there is a growing trend for individuals to measure breath alcohol prior to driving to ensure their own safety. Furthermore, in a range of workplaces there are facilities for BAC measurement to ensure safe working practices, especially where the use of heavy machinery is involved. This equipment must be manufactured according to AS 3547-1997, the Australian Standard for breath alcohol testing devices for personal use. It specifies requirements for the performance, testing and marking of breath alcohol testing devices for private use, ie not for use by law enforcement authorities. Similar to the requirements in NMI R 126, this Australian Standard also makes reference to test and calibration procedures.