Breathalysers act as important weapons in the hands of the police to administer quick roadside tests in the fight against drink driving.
India has one of the lowest permissible blood alcohol concentration rates in the world and yet driving under the influence of alcohol continues to be a major cause of road collision and fatalities
1. What is the permissible level of blood alcohol concentration in India for driving?
According to the law, individuals found with 30 ml per 100 ml of alcohol in their blood are considered incapable of driving.
2. How does a breathalyser work?
A breathalyser estimates an individual’s blood alcohol levels. When a person breathes into the device, it picks up on the molecular content of alcohol in the breath from the lungs and converts it into the approximate blood alcohol level.
When alcohol enters the bloodstream after being consumed, it is not instantly digested and chemically remains unchanged. This means that when the blood passes through the lungs, some of this alcohol, which is naturally highly volatile, evaporates into the air present there. When expelled, this is picked up by the breathalyser.
3. How accurate is the test?
While not as accurate or reliable as blood tests, the blood alcohol level readings registered by breathalysers generally comes quite close to the actual levels. However, several factors such as the improper calibration of the device, radio frequency interference and physiological differences (weight, body temperature and breathing patterns), can at times increase the margin of error.
4. Can one refuse to take a breathalyser test?
Yes. However, if an individual does refuse they are required to provide a blood sample for a lab test to check blood alcohol levels. Additionally, if the police suspect that the reason for refusal is drunkenness, they can put a person under arrest without a warrant and take them to the closest hospital or police station for a blood test.
5. What are the different types of breathalysers?
In general, three types of blood alcohol testing devices are used—conventional breathalysers, intoxilysers and alcosensors. While conventional breathalysers have a mechanism that uses a chemical reaction to produce a colour change which is then used to determine the level of alcohol in the expelled air, intoxilisers identify and count alcohol molecules in the breathed air by analyzing the vibrations caused by their absorption of infrared light.
Alcosensors on the other hand, rely on the measurement of electric currents caused in a fuel cell due to the oxidation of alcohol when it comes in contact with a platinum electrode. The more the alcohol molecules in a person’s breath, the more oxidation will take place and electric currents will be produced.
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