Last updated: 16/10/2022

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We hope you enjoy your stay, and avoid drinking alcoholic beverages while reading, as our subject today is the breathalyser.

Also called breathalyzer, it’s a piece of equipment that you’ve surely heard of. It became very popular after the approval of the Federal Law n° 11.705/08, known as Dry Law. It limits the amount of alcohol in any motor vehicle driver’s test to zero.

Respecting the law is important. But so is understanding the limits of the equipment and how it works. After all, there are several options of the product and here we will inform you about everything you need to know.


  • Some medicines have a certain alcohol content, even the chemical reaction in the digestion of some foods releases alcohol. For this reason, you may not be as safe from the positive on the breathalyser as you believe.
  • Many breathalyzer options appeared on the market after the Lei Seca (Dry Law), mainly for domestic use. They are good options to help you, but read the instructions of the product very well. A silly mistake can cost you a lot.
  • It’s important to remember that a measuring equipment needs to be calibrated and checked. Always look for the INMETRO inspection seal on the equipment you purchase.

The Best breathalyzer: Our Picks

When searching for breathalysers, you will find a good number of products on the internet. And they need to be accurate in what they tell you, to put your mind at ease. We’ll help you track down the best ones.

Buying Guide

You already know how much having a breathalyser around can help, but you also need to know how it works. By following our guide, you will find all the information you need to make a great purchase.

Guarda de trânsito lendo a medição auferida pelo bafômetro em suas mãos. Ao lado um motorista sentado em seu carro aguarda.

Understanding how the breathalyzer test works is important because it prevents you from complicated and even criminal situations. (Source: miguelrd68 / Pixabay)

Why is it important to have a breathalyzer?

Since you intend to buy a breathalyzer, it is important to know how it works, isn’t it? After all, the procedure of blowing is only part of the process.

There are several types of breathalyzers, but they all obey one rule: they are based on the chemical reaction of an agent exposed to ethyl alcohol. That’s where the technical name of the equipment comes from: ethyl breathalyzer.

According to the Federal Law 11.705/08 (Lei Seca), drivers caught with any amount different from 0.00 milligram of alcohol per alveolar air are liable to a fine and suspension of the right to drive.

That is why it is important that you have equipment capable of helping you to understand your condition. Studies indicate that each ingested dose of alcohol takes approximately 1 hour to dilute in the bloodstream.

And it gets a little more complicated, since beverages have different alcohol content. Not to mention that no person is the same as another in terms of size, weight and metabolism.

Want to know the advantages of having a breathalyser? We can help you with that.

  • Measures the alcohol content in your lungs
  • Indicates the presence of alcohol after ingesting medication with it in the composition
  • It is a cheap accessory
  • It is easy to use
  • Several pieces of equipment do not have an approved calibration

How does the breathalyzer work?

The breathalyzer works by blowing into the air. The current of air generated flows into the device, where there is a chemical agent, which will react if exposed to ethyl alcohol.

The equipment needs more than one litre of air to make the measurement, the equivalent of at least five seconds of exhaled air. So, prepare your lungs.

In the device, the “amount of” reaction is measured by circuits and sensors, which presents it in milligrams of alcohol per litre of air. The chemical process eliminates all the alcohol received, and you’re ready for the next blower.

Having alcohol in the lungs happens because our body absorbs part of everything we ingest (digestive process). And this absorption takes the contents into the bloodstream, including the alcohol in what we eat and drink.

Imagem de um brinde com várias pessoas segurando bebidas diferentes em cor e formato de copos.

The food or drink that you ingest, is absorbed and reaches the blood. Alcohol follows the same path, being exhaled through the lung. (Source: bridgesward / Pixabay)

The lung does an air filtration process, where it delivers oxygen directly into the bloodstream, and takes carbon dioxide gas from there. If there is alcohol in the bloodstream, the lung will end up “exhaling” part of it along with the carbon dioxide gas.

And that is why the breathalyzer functions as a device for indicating and measuring the alcohol content.

What types of breathalyzers exist?

As a rule, every breathalyzer works from a chemical reaction. From the most portable ones to those carried in cases, any research will lead you to several types.

Regardless of which one you intend to buy, you should take into consideration the equipment’s reliability. After all, Contran determines that the equipment must be approved by INMETRO, meeting the agency’s requirements for precision and quality.

Thinking about the breathalyzer models, we can have it of two most common types: disposable or by fuel cell:

  • Disposable: These are single-use devices, where the air is inflated in bags intended for this purpose which, after being filled, are placed in a test tube with reagent. When the air is emptied, placing the tube in the bag outlet, the reagent changes colour, indicating the presence of alcohol.
  • By fuel cell: It is the most used by the Brazilian police. The breath containing ethyl alcohol generates a chemical reaction with the compound existing inside the equipment. The result is an electrical discharge and water in the form of steam. The equipment has sensors to measure the intensity of the discharge, which is presented in g/L of alveolar air.

What can be accused in the breathalyzer?

Not only alcoholic beverages have ethylic alcohol in their composition. Some medicines, especially herbal medicines, also contain it, as well as mouthwashes.

The truth is that certain foods, soon after ingested, undergo fermentation in the stomach, also releasing a small quantity of alcohol.

And since the Dry Law determines zero tolerance, you may not even go to jail for the low level, since the Law determines jail starting from 0.33 mg/L, but you will suffer the penalty of almost £3,000.

Science explains that in these cases the alcohol will disappear in minutes, not being something to worry about. But if you drink and drive, and are stopped in a police blitz, try to explain the situation and wait a few minutes before the test.

Or else – and the most recommended – go to a laboratory (or emergency care) and ask for a blood test to verify the alcohol content.

Imagem de um laboratório, com diversos tubos de ensaio e vidraria. No centro há uma moça de costas, realizando testes.

If you do not agree with the result of the breathalyzer, you can take a blood test yourself. It overrides the result of the equipment. (Source: jarmoluk / Pixabay)

A blood test taken up to a few hours later, overrides the breathalyzer test, and you can use it as counterevidence to avoid being fined. Nor have the right to drive suspended.

After all, the objective is to know if you have alcohol in your blood, and not on your breath. The breathalyzer is here to simplify this.

Is there a tolerance for the breathalyzer?

Legally speaking, there is. The metrological legislation (equipment calibration) admits a margin of error called “maximum admissible error”.

Provided for in Contran Resolution 432/13, it states that only results equal to or greater than 0.05 mg/L are considered to establish an infraction.

How much does it cost?

Breathalyzers are really cheap to acquire. And much more affordable still when you compare their price with the amount of the fine you could get.

It is important to take into consideration, however, that a home breathalyser may not be as accurate as a police one. Pocket-sized options can be found for as little as £50. Some even have those rings for placing on the keychain.

If you want something that really works, get ready to spend a few hundred reais. Without mentioning the periodic calibrations that the manual will inform you.

Purchase criteria: What to observe when purchasing a breathalyser

By now, you can consider yourself a connoisseur of the subject. However, if you are actually thinking about purchasing the equipment, you should pay attention to a few features. When researching about the breathalyzer, focus on:

  • Calibration
  • Display
  • Portability
  • Type

Understand each of these factors below to make the best choice.


This is, without doubt, the most essential part of the equipment. Give preference to acquiring breathalyzers approved by INMETRO (they come with a seal). This condition guarantees an equipment tested in calibration and quality.

It is important to remember that the calibration of any measuring equipment should be periodic, as informed in its manual.

There are many options in the market without the INMETRO homologation, but that also have been calibrated by other agencies. Generally cheaper, they end up being the most common acquisition.

In this case, the advice is to perform the test several times in a long time interval, ensuring that the 0.00 is really 0.00.


Extremely useful for measurement, there are several devices on the market with the option of an LCD screen. There are also those whose equipment comes with three distinct lights, and those that simply change colour.

Defining which way is interesting for you that the equipment works, is a priority, because you will need to understand and deal with the measurement.

Although those with an LCD display are more practical, the equipment with colour change through chemical reaction tends to be more accurate, because if there is alcohol there will be a reaction.

Imagem de um policial segurando uma prancheta e um bafômetro.

The breathalyzer with colour change through chemical reaction tends to be more precise. (Source: Olena Kachmar / 123RF)


If you intend to purchase a breathalyzer, you must take into account its dimensions, and the accessories needed for its operation.

Some models require the use of breathalyzers or straws, which must be carried together. Others require a refill after use.

Define the level of portability you want to have, and work from there. Breathalyzers are most commonly found on drivers’ key chains.


Something we’ve already covered in the article, it’s also important that you define the type of breathalyser you intend to purchase.

Do you want something for single use due to a specific event or situation? Or a refillable device for a few uses? Or, a breathalyzer for several uses, because you intend to go out asking your friends for their breath to buy alcoholic graduation?

For the most diverse uses, define well the reasons for your acquisition, and from there look for the most adequate models.

(Fonte da imagem destacada: John Roman / 123RF)