We hear a case of drunk and drive in news somewhere every day. To avoid this kind of incident breath analyzers play their role in a good manner. Most probably you have seen this device in the hand of a policeman to determine the amount of alcohol in the system of persons suspected of being intoxicated. In the breath analyzer, a precise amount of the suspected person’s breath is passed and this analyzer displays the amount of alcohol that person. It is very helpful to identify the amount of the consumed alcohol in that person. Before going to dig the internal units of the breath analyzer, let’s have little information about the breath analyzer or breathalyzer.

What is Breathalyzer?

A breathalyzer is a gadget that measures alcohol levels in the system of a suspected person by analyzing the precise amount of alcohol in the breath. This gadget is being frequently used to secure peoples in the transportation system.

Breathalyzer for testing alcohol level

Analyzing alcohol level by using Breathalyzer

When someone drinks the alcohol it gets absorbed from the throat, stomach, mouth, and intestines into the bloodstream. Here we need to know one more point that is “Alcohol is not digested upon absorption, nor chemically changed in the bloodstream”. As of result, the blood goes through the lungs, some of the alcohol moves across the membranes of the lung’s air glands (also known as alveoli) into breathe, because alcohol will evaporate from the solution. The concentration of alcohol in the breath is related to the blood. As the alcohol is present in exhaled air, it can be detected by the testing of this air.

Units in Breathalyzers:

Now, look at the breathalyzer internal units that are present in this device.

  1. Gas sensor module
  2. Control board
  3. Power supply

Gas sensor module:

The gas sensor module contains a sensor that contains compounds like SnO2 (tin oxide), whose conductivity is low in clean air.

Gas sensor for breathalyzer

Gas sensor for breathalyzer

The conductivity of this compound increases with the concentration of the alcohol gas. A good quality gas sensor has a high sensitivity to alcohol and good resistance to disturbance due to vapor, smoke, and aerosol also. Most of the sensors are having a direct interface with the control board. A typical alcohol sensor is having high sensitivity with a fast response time. Many gas sensors have an onboard potentiometer that can be used to set the maximum gas concentration beyond which output gets triggered. This sensor module requires a 3 to 5 volts DC power supply to operate.

Control board:

The Control board is a logical unit of the breathalyzer. It is mainly responsible to make decisions, on the basis of gas sensor output. Many alcohol or gas sensors output is in digital form so it can directly interface with the control board. We can choose various circuit boards as a control board based on our requirements. There are mainly two kinds of logical units being used – Microcontroller-based Arduino-Uno and Raspberry-Pi.

Arduino in breathalyzer

Arduino in breathalyzer

The Control board comes with a pre-programmed microcontroller or memory. It uses small software to represent alcohol levels on the display unit. In modern breathalyzer, LCD display is being used whereas some of the old modeled analyzers are having LED indicators to represent the alcohol level. You can also program your analyzer circuit but you need to know to program in java or assembly languages. At present time sophisticated breathalyzers that are using Raspberry-Pi or Arduino-Uno can perform multiple functions also with detecting the alcohol level.

Power supply:

Portable breathe analyzers are having a rechargeable 5 volts battery. As we know most rechargeable batteries are based on lithium-ion. The power supply unit provides power to every electronic unit like gas sensor, control board, and some LEDs also.

Working process:

When a person consumed alcohol and exhale air into the breathalyzer then the gas sensor plays its role. The conductivity of the gas sensor compound will be changed on the basis of alcohol concentration. And this sensor generates output that is being processed by the control board. The control board will work as a brain that makes decisions and send the data to the display unit to show the alcohol level.


Modern breathalyzers are fairly accurate, but they are not perfect. Its accuracy mainly depends on the gas sensor whereas the control board comes second in this. The analyzers are having a margin of error, as any device can, and can be off as much as .01%.


Breathalyzers are the most preferred gadget to check the blood alcohol level, as they provide fairly accurate and quick results. Unlike other methods where blood or urine samples are collected, which takes much time and effort to inspect. I hope this article helps to understand Breathalyzers.

Thanks for reading. See you soon with another exploration!

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