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The majority of breathalyzers utilize one of three technologies for detecting Blood Alcohol Content or Blood Alcohol Concentration (BAC): a semiconductor oxide sensor, a fuel cell sensor, or a spectrophotometer. The spectrophotometer is commonly employed in large, table-top breathalyzers typically located at police stations.

Blood Alcohol Content or Blood Alcohol Concentration, abbreviated BAC, is the concentration of alcohol in a person’s blood. BAC is most commonly used as a metric of intoxication for legal or medical purposes, and it’s usually measured as mass per volume. For example, a BAC of 0.05% means 0.05 grams of alcohol per 100 grams of a person’s blood, or 0.5 grams of alcohol per 1000 grams of blood.

Factors that affect your BAC include the following:

• Age – As you age, the intoxicating effects of alcohol become increasingly pronounced.
• Gender – Alcohol is highly water soluble. Because women generally have lower water content in their bodies than men, they usually reach a higher BAC if they consume alcohol at a similar rate to their male counterparts, even if they are the same age and weight. Women also have a lower quantity of an enzyme in their stomachs that breaks down alcohol than men.
• Rate of Consumption – The faster you consume alcohol, the faster your BAC will rise.
• Drink Strength – The more alcohol a drink contains, the more will end up in your bloodstream.
• Body Type – The more you weigh, the more water you tend have in your body, which has a diluting effect on the alcohol you consume. That’s why larger people usually require more drinks to “keep pace” with their smaller companions.
• Fat/Muscle Content – Fatty tissue is low in water content and cannot absorb alcohol, and the alcohol must remain in the bloodstream until the liver can break it down. However, tissues that are higher in water content, such as muscle, do absorb alcohol. Hence BAC will usually be higher in the person with more body fat.
• Metabolism – “Metabolic tolerance” varies from person to person and describes the rate at which alcohol is processed by the body.
• Emotional State – Stress can cause your body to divert blood from your stomach and small intestines to your muscles, and slow down the rate of absorption of alcohol into your bloodstream. When you calm down and your blood flows normally again, you may experience a surge in your BAC.
• Medications – Many medications react negatively with alcohol, including cold or allergy pills and prescription drugs. They can intensify the effects of alcohol and even endanger your health. If you are taking meds, check the product labels for alcohol warnings, or consult your doctor or pharmacist before you drink.
• Food – If you drink alcohol on an empty stomach, your BAC will be higher than a person who has eaten before drinking. Food slows the absorption in your bloodstream by keeping the alcohol you consume in your stomach and for a longer period of time.
• Carbonation – Carbonated drinks such as sparkling wine or champagne, or mixed drinks with sodas may increase the rate at which alcohol passes through your stomach and result in a higher BAC.
• Diabetes – Alcohol can affect the glucose levels of people who have diabetes and cause hypoglycemia. Diabetics should consult their doctors about drinking alcohol and avoid drinking on an empty stomach.
• Alcohol Intolerance – Alcohol may cause adverse reactions in some, including flushing of the skin, nasal congestion, elevated heart rate, and reduced blood pressure. According to the Mayo Clinic, alcohol intolerance is caused by a “genetic condition in which the body is unable to break down alcohol.

How do I use my breath alcohol tester?

For most models, a user simply blows through the mouthpiece for 5 seconds. The blowing is similar to blowing out a candle and the user should blow evenly for the entire 5 seconds. The breathalyzer will indicate when to start and stop blowing, and if the sample was not adequate for an accurate reading.

The sensors measure the alcohol level of air in the deep lungs. This value is converted into the corresponding Blood Alcohol Content (%BAC) estimate. Testing is most accurate if subjects have not consumed food or alcohol 15 minutes prior to testing to ensure that there is no residual mouth alcohol.

Why must I wait 15 to 20 minutes after consuming food or alcohol to ensure testing results are accurate?

A breathalyzer is able to calculate this percentage using only a breath sample because of the precise relationship between alcohol in the blood and alcohol metabolized into the lungs from the bloodstream. As such, it is important to make sure the mouth is clear of contaminant (including alcohol) so that the breath sample contains pure lung air, or as close as possible.

What type of maintenance is required to maintain a personal or professional breathalyzer? Do they require calibration?

Over time, all alcohol testers need to be re-calibrated to maintain accuracy. Calibration is a process of checking and adjusting the accuracy of a unit by comparing its results with a known value. For example, a known 0.080 %BAC gas concentration is blown into a breathalyzer, and the unit is adjusted to make sure it correctly reads 0.080 %BAC.

This process is sort of like winding a clock. When the clock is first set it displays accurate time. However, over time the clock gradually drifts a few minutes, and eventually can be off by quite a bit if you do not occasionally reset the clock. When selecting an alcohol tester, it is imperative to select a unit that is capable of being calibrated.

How often should I calibrate my breathalyzer to ensure accuracy?

We recommend re-calibrating breathalyzers with semi-conductor sensors every 300 tests or once a year, whichever one comes first. Breathalyzers with fuel cell sensors will remain accurate for thousands of tests, but should still be re-calibrated annually. Additionally for these models, using the breathalyzer regularly can actually help keep it accurate, as the moisture in exhaled human breath is beneficial to the sensor.

See our Calibration FAQs for more information and to complete a form to send your breathalyzer to us for calibration. Our trained technicians will perform a full diagnostic check on all aspects of your breathalyzer as part of the calibration process.