What is an Éthylotest and How Does It Work?

An éthylotest (commonly referred to in English as a breathalyzer) is a device used to screen for alcohol in a person's system by measuring the concentration of ethanol in their exhaled breath. In the context of French road safety and the Code de la Route, these devices are categorized into two primary types:

• Chemical Éthylotests (Disposable Balloons): These single-use kits consist of a plastic balloon and a glass tube containing chemical reagents (specifically potassium dichromate). When a driver blows into the balloon and forces the air through the tube, any alcohol in their breath undergoes an oxidation-reduction reaction. This chemical reaction causes the yellow/orange crystals inside the tube to turn green. If the green coloration crosses the printed limit line, the driver is over the legal limit.
• Electronic Éthylotests: These reusable digital devices utilize electronic sensors to analyze breath samples. They display the estimated blood alcohol concentration directly on a screen, usually measured in milligrams per liter of exhaled air (mg/L) or grams per liter of blood (g/L).

Both types of éthylotests are highly sensitive to environmental factors. For example, chemical tests must be stored at temperatures between -10°C and +40°C. Leaving them in a vehicle's glove compartment during a hot summer or a freezing winter can degrade the chemical compounds, rendering the test highly inaccurate.

Éthylotest vs. Éthylomètre: Understanding the Key Difference

One of the most frequent traps on the French driving theory exam is confusing the éthylotest with the éthylomètre. For the exam and real-world legal situations, you must understand their distinct legal roles:

1. The Éthylotest (Screening / Dépistage): This device is used only for preliminary screening. It indicates whether alcohol is present above or below the legal threshold. It does not provide a legally binding measurement. If a driver tests positive on a roadside éthylotest administered by law enforcement, the officers cannot issue a fine or points deduction based on this result alone.
2. The Éthylomètre (Verification / Vérification): This is a highly precise, calibrated, and officially certified machine located in police stations or specialized mobile vehicles. It measures the exact concentration of alcohol in the breath down to the decimal point. Only the measurement recorded by an approved éthylomètre (or a subsequent medical blood test) holds legal validity for issuing traffic citations, license suspensions, or court summonses.

Legal Alcohol Limits and Thresholds in France

When preparing for the theory exam, you must memorize the exact blood alcohol concentration (BAC) thresholds used in France. These limits correspond directly to how an éthylotest is calibrated:

• Standard Drivers: The legal limit is 0.5 grams of alcohol per liter of blood (0.5 g/L), which corresponds to 0.25 milligrams of alcohol per liter of exhaled air (0.25 mg/L). If an éthylotest registers at or above this level, the driver is in violation of the law.
• Novice and Probationary Drivers (Jeunes Conducteurs): Novice drivers (those within their 3-year probationary period, or 2 years if they completed accompanied driving) are subject to a much stricter threshold of 0.2 grams of alcohol per liter of blood (0.2 g/L), which corresponds to 0.10 milligrams of alcohol per liter of exhaled air (0.10 mg/L). Because even a single standard alcoholic beverage can push a person over this limit, this rule functions effectively as a zero-tolerance policy.

Is Carrying an Éthylotest Mandatory in France?

The legislation surrounding the carrying of breathalyzers inside vehicles in France has evolved significantly over the past decade.

In 2012, a decree was passed requiring all motor vehicle drivers (except mopeds) to carry an unused, unexpired éthylotest in their vehicle. However, due to supply chain shortages and ongoing debates over device reliability, the penalty fine for failing to carry one was repeatedly postponed and eventually abolished.

Ultimately, on May 22, 2020, the French government officially abolished the requirement to carry an éthylotest in vehicles entirely. Today, you will not receive a fine or point penalty for not having one in your car. Despite this, road safety organizations and driving instructors strongly recommend keeping self-test kits in your vehicle to promote responsible self-evaluation before driving.

Common Code de la Route Exam Pitfalls

Theory exam questions often try to trick candidates regarding the administrative and physical aspects of breathalyzers. Keep these core facts in mind:

• Expiration Dates: Chemical breathalyzers have a limited shelf life (usually around two years). An expired test is legally and practically useless. For a self-test to be reliable, the packaging must bear the official French "NF" certification mark and be within its validity date.
• Right to a Second Test: If you undergo a verification test with an éthylomètre following a positive screening, you have the legal right to request a second measurement immediately. The police are required to inform you of this right, and the lowest of the two recorded values will be used for any legal proceedings.
• Refusal to Test: Refusing to submit to an éthylotest screening or a subsequent verification is treated as a major criminal offense in France. It carries the exact same severe penalties as driving with a high blood alcohol concentration (including automatic license suspension, heavy fines, and potential imprisonment).