About This Article
Zoom Testing has more than 20 years’ experience supplying alcohol and drug testing products in the UK. This article explains why breathalyser sensors require periodic replacement or calibration, how long they typically last, and the signs that a sensor may need attention.
Published: 20 January 2024 | Last Updated: 7 October 2026 | By: Anthony Cunningham
Today’s digital breathalysers are calibrated at the factory to ensure that the sensors provide accurate readings. Eventually, alcohol and other contaminants in the environment can affect the sensor and ultimately reduce the accuracy of the readings.
Breathalysers that have fixed sensors normally need to be returned to a service centre for recalibration. Breathalysers that have replaceable, pre-calibrated sensors, like the AL6000 breathalyser, can instead have the sensor module replaced.
How does a Breathalyser Work?
In order to understand why it is important to regularly change the sensor in your breathalyser, it is worth knowing how a breathalyser works.
As soon as you have a drink, alcohol is digested and begins to enter the bloodstream via the stomach wall. In general terms, neat alcohol drunk on an empty stomach will enter the bloodstream quicker than a less potent drink (for example, a milk based cocktail) drunk on a full stomach. This does not mean that drinking a neat spirit will make you drunker, it just means that the effect is probably going to be felt much quicker.
Once alcohol is in your blood it moves around your body, producing all the usual physical brain and body effects that you feel when you have had a drink. The liver’s job at this stage is to slowly filter the alcohol out of your bloodstream. With each “pass” more alcohol is filtered out until eventually no alcohol remains in the body.
As well as being present in the blood, alcohol passes into the air in the lungs. When you breathe out, alcohol in this deep lung air can be measured by a breathalyser.
When using a breathalyser, follow the instructions supplied with the particular device. For the AL6000, the manufacturer advises waiting at least 20 minutes after eating or drinking before testing. Alcohol remaining in the mouth can interfere with the test and produce an artificially high reading.
As you can see from this explanation, a breathalyser works by detecting very low concentrations of alcohol. Smoke, saliva and other contaminants should not be blown into the device, as they can affect or damage the sensor. This is also why the sensor needs periodic replacement or calibration to help maintain accurate operation.
For what length of time will the breathalyser sensing unit retain its accuracy and reliability?
There is no single replacement interval that applies to every breathalyser. Always follow the maintenance schedule specified for your particular model. For the AL6000, manufacturer guidance recommends replacing the sensor module after around 200 tests or at least once a year, whichever comes first. The AL7000 has similar periodic sensor replacement requirements.
The sensor may lose accuracy more quickly depending on factors such as:
- Exposure to intense heat, such as being left in a vehicle during hot weather
- Exposure to severe cold
- Repeated exposure to high concentrations of alcohol
- Moisture build-up or inadequate ventilation after use
- Exposure to smoke, chemicals or other contaminants
Heavy use or repeated high alcohol readings may mean that a sensor needs replacing sooner than its normal maintenance interval.
What tests can I perform to ensure that the breathalyser sensor is providing accurate readings?
If you are unsure of the age of your sensor or how it has been stored, inconsistent results can be a warning that the sensor requires attention. Repeated readings that vary unexpectedly, persistent error messages or results that appear unusual may indicate that the sensor needs replacing or that the breathalyser requires calibration or servicing.
A series of home tests cannot confirm that a breathalyser is correctly calibrated. If accurate readings are important, follow the manufacturer’s maintenance instructions and replace or professionally calibrate the sensor at the recommended interval.
Replacement AL6000 Sensor
We can offer a replacement sensor for our popular AL6000 Breathalyser. These sensors are calibrated in mg/l. To replace an existing unit, please ensure that you have a unit with a RED circuit board and a BLUE coloured circle on the sensor. Breathalyser units that have a GREEN circuit board, or a coloured circle that is not blue, cannot be replaced with this sensor.
Replacement AL7000 Sensor
If you are looking to replace the sensor in an AL7000 breathalyser, the AL7000 uses a replaceable pre-calibrated sensor module that can be changed by the user. Manufacturer guidance for the AL7000 recommends periodic sensor replacement, typically after around 200 tests or at least once a year, whichever comes first. Some versions of the device may also display a calibration or sensor warning after a specified number of tests, so always follow the instructions supplied with your particular unit.
When to Replace the Sensor in your Breathalyser
The sensor in your breathalyser is a delicate instrument that can lose accuracy over time. The correct replacement interval depends on the model and how it is used, but there are some signs that may indicate that the sensor needs attention sooner:
- Inconsistent results. Repeated readings that vary unexpectedly may indicate that the sensor is losing accuracy.
- Error messages or unusual results. Frequent sensor-related error codes or results that appear abnormal may mean that the sensor needs replacing or the unit requires servicing.
- Changes in storage or operating conditions. Exposing the breathalyser to extreme temperatures, high humidity or contaminants such as smoke or cleaning products can affect the sensor.
- Heavy usage. Breathalyser sensors gradually deteriorate with use. Follow the test-count and time interval specified by the manufacturer rather than relying on age alone.
- Old stock or uncertain history. If you do not know the age, usage or storage history of a sensor, consider replacing it before relying on the breathalyser.
Replacing a pre-calibrated sensor module is designed to restore the breathalyser to its specified operating condition without the sensor itself having to be sent away for recalibration. It is still important to follow the instructions for the particular breathalyser and sensor being used.
While breathalyser sensors are designed to maintain accuracy during normal use, excessive exposure to extreme conditions or contaminants can accelerate deterioration. Adhering to proper care and storage procedures can help extend sensor life:
- Allow the breathalyser to dry and ventilate as directed after use.
- Keep the breathalyser away from extreme temperatures. Avoid leaving it in a hot or very cold vehicle.
- Store the breathalyser in a clean, dry location away from chemical fumes or smoke.
- Do not allow liquids or cleaning agents to come into direct contact with the sensor.
- Follow the manufacturer’s usage, storage and maintenance instructions.
With appropriate care and regular maintenance, a good-quality breathalyser can provide consistent readings for personal or workplace screening. Replacing or recalibrating the sensor at the interval specified by the manufacturer helps maintain the accuracy and reliability of the device.
About the Author
Anthony Cunningham, BA (Hons), MA, is a UK-based drug testing expert and editor with over 20 years’ experience running Zoom Testing, a trusted source for accurate drug testing kits and testing guidance. He creates clear, evidence-based articles using UK legislation, workplace compliance standards, and harm reduction best practices. Where possible, content is reviewed by testing specialists and compliance professionals to enhance accuracy and reliability, helping readers make informed testing decisions.
Alcohol Testing Disclaimer
This article is for general information only. Breathalyser readings can be affected by the device, sensor condition, calibration, testing technique and other factors. Do not use a consumer breathalyser as a reason to drink and drive or assume that it is safe to drive. Where an alcohol test result could have legal, employment or safety consequences, appropriate professional testing and advice should be considered.
