Product Review: Personal Breathalyser Group Test

Disclosure: I received free sample units for the purpose of this review. I received no payment and was not required to write a positive review.

We all know that you should not drive directly after drinking, but did you know that 17% of drink driving prosecutions are of people caught driving the morning after*? With the festive party season approaching, this is a particular risk. Drivers may get up early for work, following a party the previous night.

Alcohol takes time to leave your bloodstream and you can still be over the limit the next morning. As a general rule, it takes an adult with a healthy liver one hour to break down one unit of alcohol, but this can vary.

I wanted to find out how easily this could happen to me. To help me do this safely and legally, I arranged to test some of the most popular personal breathalysers on the market – products that are not expensive and are readily available on the high street. It’s worth noting that these are amongst the cheapest breathalysers available, so cannot be expected to provide the same level of accuracy and durability as more expensive units (for information on other types of breathalyser, click here).

What are personal breathalysers?

Beer and whisky to test breathalyser
After drinking the night before, you may still be over the limit the next morning

Personal breathalysers are cheaper alternatives to the much more expensive units used by the police. The most common type are reusable electronic devices that are similar in size to a small mobile phone and cost around £20-£60. There is also another type – a chemical device that you blow into and can only use once.

All these products work by measuring the amount of alcohol in your breath. When you have been drinking, a certain amount of the alcohol in your blood evaporates as the blood passes through your lungs. This means that when you breathe out, your breath contains alcohol. It is possible to calculate your Blood Alcohol Concentration (%BAC) by measuring breath alcohol, and this is how most personal breathalysers work.

These breathalysers are NOT intended for use after drinking to see if you can still drive. Readings taken directly after drinking are likely to be inaccurate as your body may still be absorbing the alcohol. The purpose of these devices is to check that you are legal to drive the morning after drinking.

The Products

AlcoSense Lite (£34.99, available direct from AlcoSense or at Halfords and other high street stores)

AlcoSense Lite breathalyserThe AlcoSense Lite was the most expensive of the three products I reviewed, although AlcoSense do make a more expensive model, the Elite (£59.99). The Lite is similar in size to a mobile phone and requires you to blow into a tube.

It has a screen that displays breath test results, along with illuminated warning symbols if you are close to the limit or if you are over the limit and unfit to drive. For readings below 0.2%, it simply displays ‘LO’, not a number. The instructions advise that you should only drive if you get a LO reading – advice I would endorse.

When you first insert batteries into the Lite, it will automatically start cleaning the breath sensor. This takes about ten minutes and the instructions recommend that you do this periodically, if the unit has not been used for a while.

In Use: To perform a breath test, you insert one of the blow tubes (provided) into the blow hole and press the power switch. The device will count down to zero and then display ‘BLOW’ on the screen. At this point you hold down the ‘BLOW’ button and blow into the tube until the Lite beeps at you. Your test result is then displayed on the screen, in BAC (Blood Alcohol Concentration) format. For example, 0.8% means you are at or above the legal limit of 80mg alcohol per 100ml of blood.

AlcoSense ONE (£24.99, available direct from AlcoSense or at Halfords and other high street stores)

AlcoSense ONE personal breathalyserThis is the smaller and cheaper of the two electronic breathalysers I tested. Instead of blowing into a tube, you blow over a sensor that is located on the top end of the device. The device itself is a similar size to a cigarette lighter and is very slimline – easily pocketed or kept in your car’s glovebox. It has a small, backlit screen to display instructions and test results – this is clear enough and can be used in the dark, thanks to the red backlight. The ONE seemed well made and simple to use and the two AAA batteries required were included with mine.

In Use: The ONE has a simple calibration setting that you perform before first use (at a time when you have not been drinking). To perform a breath test you press the on/off button, wait while the device counts from 5 to 1 and beeps and then blow over the sensor until the device beeps again.

Test results are displayed in BAC format, but with an extra decimal place compared to the Lite. For example, 0.08% represents a blood alcohol level at or above the legal limit of 80mg alcohol per 100ml of blood.

The Original Breathalyzer Morning After Test (£4.99, available at Halfords)

Original Breathalyser Morning After TestThis is a chemical product that can only be used once. The makers say that it is based on the same technology that the police used to use, presumably some years ago, before the current electronic devices were introduced. The box contains a plastic tube that contains crystals that change colour when you blow through them, depending on the amount of alcohol in your blood. To test your breath, you bend the tube at each end to break the seal and then insert one end into the plastic bag that is provided.

You then blow through the tube until the bag is full. The crystals in the tube will start to go green. If the green extends beyond a line on the tube, you are over the limit of 0.8% (measured as 80 milligrammes of alcohol per litre of blood).

The Test

My testing took place over an evening and I drank roughly what I would normally drink on a Friday evening. This would not normally be enough to make me feel hungover or to stop me driving the following morning.

I have not disclosed the amount I drank for the test here as people’s bodies absorb and breakdown alcohol at different rates and I would not like to give the impression that I was defining how much can or can’t be drunk before driving.

The instructions for the Lite said that it takes 90 minutes after drinking for the alcohol to be distributed evenly thoughout your bloodstream – so I planned a breath test 90 minutes after I stopped drinking, along with other later tests to simulate getting up early the next morning. Both the Lite and the ONE said that they should not be used less than 30 minutes after stopping drinking, as the sensor might be damaged and the result would be inaccurate.


Remember that all results are +/- 0.2% (Lite) or +/-0.02% (ONE). These are the manufacturer’s specified accuracy levels.

A reading of 0.8 on the Lite is equivalent to a reading of 0.08 on the ONE:

Examples of test results on breathalysers
Some example readings

40 minutes after drinking:

  • AlcoSense Lite: 0.7
  • AlcoSense ONE: 0.09

90 minutes after drinking:

  • AlcoSense Lite: 0.6
  • AlcoSense ONE: 0.09

5.5 hours after drinking:

  • AlcoSense Lite: LO (<0.2)
  • AlcoSense ONE: 0.04

7.5 hours after drinking:

  • AlcoSense Lite: LO (<0.2)
  • AlcoSense ONE: 0.00

As you can see, I was not over the limit the next morning.

Disclaimer: All test results are based on my personal testing only. Different people will experience different results – people’s bodies process alcohol at different rates. I did not have a calibrated (police) breathalyser with which to compare my results, so cannot be sure of their accuracy.

Are they accurate?

The UK drink driving limit is defined in three ways, all of which are equivalent and can be used by the police to test people for drink driving:

– 80 milligrammes (mg) of alcohol per 100 millilitres (ml) of blood (80mg/100ml)
– 35 microgrammes of alcohol per 100ml of breath
– 107mg of alcohol per 100ml of urine
(Source: November 2010)

The breathalysers I tested display results in the form of Blood Alcohol Concentration. According to AlcoSense, both devices are accurate to +/- 0.2% BAC – in other words, a reading of 0.7% on the Lite could indicate a true BAC of anywhere between 0.5% and 0.9%. For this reason, you should not consider driving unless the devices are giving a 0% or LO reading (the Lite reads LO for readings below 0.2%).


Both the AlcoSense breathalysers I tested are useful devices to make sure you are clear of alcohol before driving the next morning. In my opinion, you should not consider driving unless you have a LO or 0% reading. This is also what the manufacturers recommend.

The reason I tested myself 30 and 90 minutes after finishing drinking was because I wanted to try and get an ‘over the limit’ reading from both machines, which I could compare with the readings taken early the next morning. These products are not intended to test whether you are fit to drive directly after drinking.

My Results: I was surprised by my breath test results, as I did expect them to be a little higher. I was also dismayed that the readings from each device were always different to each other. Could they be trusted?

AlcoSense Lite: The Lite was very consistent. Each time I used it, I repeated the test a few minutes later and always got the same result again. This device was definitely the better of the two Alcosense units and is worth the extra money.

AlcoSense ONE: My feeling is that the ONE is more prone to user error. I found that results could vary depending on how close I held it to my mouth.

Original Breathalyser Morning After Test: Unfortunately I could not make this breathalyser work. Even though I blew as hard as I could through the tube (until I felt light-headed) I could only get a tiny amount of air through the tube. I could not inflate the bag. This product is affordable for occasional use but I am concerned that if stored for any length of time, it may not work when required.

*Source:, November 2010.

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