Breath testing, BAC, & best practice

If you’re looking to start a conversation about blood alcohol concentration (BAC) or drink driving at an event, using a breathalyser as a prop can be a tempting option. But in addition to the equipment being expensive and requiring regular calibration to be accurate, it’s not a great strategy if you’re trying to get people to reduce their drinking. Find out what other, potentially more effective, tactics you could use.

Because the bigger problem we’re tackling is to reduce the harms from alcohol, inadvertently sending the message that if you’re not driving it doesn’t matter how much you’re drinking could undermine the message we’re really trying to send.

Focusing on changing the drinking culture at events for everyone, not just drivers, can have a greater positive impact on the community by addressing all of the harms beyond drink driving that come from risky drinking.

Why breath testing is risky

People can show impairment at low BACs

Some people may be dissuaded from driving if they find out their BAC is 0.05% or over, however it’s also possible that a BAC of 0.04% might encourage someone who didn’t intend to drive to do so. Potential drivers may mistakenly believe that there’s little or no risk if they drive within the legal limit of 0.05% – but just because it’s the law doesn’t mean it’s the safest choice.

Degrees of impairment may be demonstrated even at low BACs. The current limit for BAC has been debated in the past, and when Victoria Police suggested a limit of BAC 0.02% the ADF supported a trial of the idea. Some research suggests that reducing the BAC limit may reduce alcohol-related road accidents.¹ ² ³ Countries like Sweden, Norway, Japan, and recently China have limits of 0.02% BAC for driving.

BAC calculations involve guesswork

Even when a driver is informed about BAC, calculating it without using a breathalyser every time is pretty tricky. It’s not just a person’s age, weight, and sex but also how much they’ve had to eat that day, their amount of body fat, and their level of experience with alcohol.

Although personal smartphone breathalysers have recently hit the market for $50-$100, their accuracy varies and the average person seems unlikely to purchase one. Human error is also an important factor when considering the value of a personal breathalyser. For example, if someone hasn’t waited long enough before testing they could have a legal BAC when leaving a venue and an illegal one 30 minutes later. Even if an expensive and properly calibrated breathalyser is used correctly, it isn’t perfectly accurate – even the police will perform a blood test to follow up a breath test that returns an over the limit result.

The safest option is not to drive when you drink – and even when you’re not driving, drinking to excess is still risky.

‘Scoring’ a high BAC may possibly be seen as a game

Breathalysers at licensed venues have reportedly been occasionally used as competitions between mates to get the highest ‘score’.4 There are concerns that personal smartphone breathalysers are sometimes used in the same way. A BAC ‘competition’ could be incorporated into one of the many drinking game apps that are already out there.

Next-day driving is also a problem

Many people might not know how long it takes to get back to a zero BAC after a night of drinking. Factors like what your BAC was when you went to sleep, how long you slept, and how healthy your liver is all affect your BAC the next morning. In some cases, it can take a full day or longer for BAC to return to zero. The Centre for Road Safety NSW says that ‘many people are booked for drink driving the next day’.

Even if they were responsible the night before, driving home after staying at a friend’s house or going back to pick up their car could be risky. It could also be mixing intoxication with fatigue.

Alternatives to breath testing

Not sure breath testing is going to achieve your objectives? Here are some alternatives according to different goals:

Trying to reduce harmful drinking at an event?

  • Best practice is to engage in primary prevention, such as working to change the drinking culture at the event.
  • The NSW police list culture change around excessive drinking as one of their priorities in the 2014-2018 alcohol strategy, and commit to ‘empowering communities to take action… to reduce the demand for alcohol’.5 Your local police are great allies, so partner up!

Trying to start a conversation about BAC and standard drinks?

  • If you want to use a prop to start up conversation, consider using your phone. There are several BAC estimator apps out there (like AlcoDroid for Android phones and IntelliDrink for iPhones). You could get people to guess first and then see an estimation of their BAC, like with a breathalyser, but avoiding the confusion that the reading is accurate enough for someone to make a decision to drive. It’s necessary to emphasise that when you’re chatting with people so they don’t get the wrong idea. Both apps also give an estimation of how long it will take until you’re sober again.
  • Knowledge quiz: keep score to stir up some friendly competition. Consider recording the results of your quiz (anonymously). Having a record of people’s knowledge around how alcohol affects them may help direct your efforts in the future, or help you put together a media release. See the sample quiz at the bottom of the article for ideas.
  • ‘Pour a standard drink’ challenge: set up beer pot and pint glasses, a wine glass, and a sparkling wine flute and see who can accurately pour what a standard drink would be in that vessel. Having pre-prepared amounts of water (e.g. 100ml to pour into the wine glass) will make it quick and easy to demonstrate. If you don’t want to bother with the props, the app On Track with the right mix (for Android and iPhone) has a digital drink measuring tool.

Trying to prevent/ reduce drunk driving from an event?

  • Consider running a shuttle bus service that can be promoted prior to the event. That way, people can decide in advance not to drive instead of facing the hassle of returning the next day for their car (which might discourage people from taking the shuttle home). Encourage event organisers to print shuttle information with tickets, or feature it on their website.
  • Are there public transport options to and from the event? Think about how you can share information on their location and cost. Talking to event organisers about promoting that information with tickets and on websites prior to the event is a good place to start.
  • There are several anti-drink driving campaigns run in NSW. Plan B emphasises the need to have a plan for getting home at the end of a night out and Stop it… Or cop itreminds people that they can get caught drink driving. You could contact the Centre for road safety to see if you can promote their campaigns in your communities.

Work with the pros

If you still think that breath testing is the best option for your community, consider working with the following organisations.

  • NSW police run random breath testing (RBT) programs, which are considered to have helped significantly with the reduction of drink driving.6 Drivers believing that they have a high risk of being caught by police is an important element of successfully deterring drink driving, so creating and maintaining awareness of RBT is important for it to work as a deterrent.6 Think about ways you can do that prior to the event, like using local media, discussing printing information about RBT with tickets, and partnering with your local police.
  • STEER is a ‘youth safe transport project’ that provides voluntary breath testing at festivals and various other events. They are based in the Northern Rivers, but are open to operating in a wider area so you could contact them about potential partnerships.
  • You can also contact your local council to discuss having a road safety officer attend your event to conduct breath testing. Some road safety officers serve multiple councils.

If you do use a breathalyser consider also promoting some of the key messages listed above under ‘Why breath testing is risky’.

Sample BAC quiz

Use this sample quiz to educate people about the effects of alcohol on BAC. Pick and choose questions that you like, and add questions that are relevant to your specific event – just make sure that you’ve got them backed up with evidence, and don’t over-exaggerate the harms.

  1. What does BAC stand for?
    Blood alcohol concentration.
  2. Is a strong coffee or a shower the fastest way to sober someone up in a hurry?
    Neither! The only thing that can sober you up is time.
  3. Aside from body composition, size and genetics what else affects how your BAC rises?
    If you ate before drinking; if you’re sick or getting over an illness; if you’re taking some prescription or over-the-counter drugs; if you have experience with alcohol.
  1. Explain what it means to have a BAC of 0.04%. 
    There are 0.04 grams of alcohol in every 100mls of blood in your body.
  2. Does your body’s ratio of fat and muscle affect how your BAC rises?
    Yes. Because muscle absorbs alcohol but fat doesn’t, the more body fat you have the faster your BAC rises.
  3. If your liver is healthy, how much alcohol can it metabolise in an hour?
    Just under one standard drink.
  4. Does your gender affect your BAC?
    On average, yes. Because women tend to be physically smaller and have more fat than muscle, their BAC can rise more quickly.
  1. Do genetics play a role in how your body absorbs alcohol?
    Yes, because alcohol is broken down by enzymes in the liver and your genes affect how many enzymes are present and how fast they work.
  2. How much alcohol is in an Australian standard drink?
    10 grams of alcohol.
  3. After a night of drinking, how many hours does it take to be completely sober again?
    It depends on your BAC when you went to sleep, and how long you slept for. Because a healthy liver metabolises just under one standard drink per hour, it is however long it takes your body to process the amount in your blood. So chances are if you had a big one, you’re going to blow over the next morning.
  1. T. Norstrom and H. Laurell, “Effects of the lowering of the legal BAC limit in Sweden,” Alcohol, drugs and traffic safety, pp. 87-94, 1997.
  2. E. Desapriya, S. Shimizu, I. Pike, S. Subzwari and G. Scime, “Impact of lowering the legal blood alcohol concentration limit to 0.03 on male, female and teenage driver involved alcohol-related crashes in Japan,” International journal of injury control and safety promotion, vol. 14, no. 3, pp. 181-187, September 2007.
  3. D. P. Phillips and K. M. Brewer, “The relationship between serious injury and blood alcohol concentration (BAC) in fatal motor vehicle accidents: BAC = 0.01% is associated with significantly more dangerous accidents than Bac = 0.00%,” Addiction, vol. 106, no. 9, pp. 1614-1622, September 2011.
  4. N. Haworth and L. Bowland, “Estimation of Benefit-Cost Ratios for Coin-Operated Breath Testing,” Monash University Accident Research Centre, 1995.
  5. NSW Police, “NSW Police Force 2014-2018 Alcohol Strategy,” 2015.
  6. K. Terer and R. Brown, “Effective drink driving prevention and enforcement strategies: Approaches to improving practice,” Trends and issues in crime and criminal justice , no. 472, 2014.
  7. D. J. Beriness and H. M. Simpson, “The Safety Impact of Lowering the BAC Limit for Drivers in Canada,” The Traffic Injury Research Foundation, Ottawa, 2002.