23 March 2015

Test Your Breath- Science and Law behind Breathalyzers

Authored by Sumeir Ahuja

Everybody fears the breathalyzer. Whether you are driving home after a few drinks or returning to campus after enjoying Haryana’s low liquor tax. So what exactly is a Breathalyzer and what are the laws and limitations with regards to its use?
A breathalyzer is a device for estimating blood alcohol content (BAC) from a breath sample. The Indian Law in relation to the use of the breathalyzer is found in Section 185 of the  Motor Vehicles Act, 1988, which states:

'Driving by a drunken person or by a person under the influence of drugs is prohibited. It prescribes a maximum permissible BAC of 30 mg %, "in a teast by a breathalyzer", while driving in India.'

Who can ask you to take a Breath Test? 
Only a police officer in uniform or an officer of the Motor Vehicles Department who has reasonable cause to suspect you for being drunk can ask you for specimens of breath for a breath test, when you are driving or attempting to drive a vehicle. In case you are involved in an accident the officer can ask you for one or more specimens of breath for breath test at the hospital (in case he is hospitalized) or otherwise on the spot or at the nearest Police Station.

What is the science behind it all?
Breathalyzers do not directly measure blood alcohol content or concentration, which requires analysis of a blood sample. Instead, they estimate the BAC indirectly by measuring the alcohol in one's breath. For medico legal purposes, breath alcohol content is measured from an end expiratory volume. Measurements by this method necessarily underestimate the alveolar breath alcohol content, and thereby, underestimate the blood alcohol content.”

When a person drinks an alcoholic beverage, about 20 percent of the alcohol is absorbed in the stomach and about 80 percent is absorbed in the small intestine. After absorption, the alcohol enters the bloodstream and dissolves in the water of the blood. The blood carries the alcohol throughout the body. The alcohol from the blood then enters and dissolves in the water inside each tissue of the body. Once inside the tissues, alcohol exerts its effects on the body. The observed effects depend directly on the Blood Alcohol Concentration (BAC), which is related to the amount of alcohol consumed. The BAC can rise significantly within 20 minutes after having a drink.

The BAC increases when the body absorbs alcohol faster than it can eliminate it. Alcohol intoxication is legally defined in terms of the level of BAC. If a person's BAC measures 0.03, it means that there are 0.03 grams (i.e., 30 mg) of alcohol per 100 ml of blood. This is the limit in India. However, there is no BAC calculator that is 100% accurate, because of the number of factors that come in to play regarding the consumption, absorption and reduction (burn off rates) of different people. These factors include sex of the drinker, rates of metabolism, health issues, medications, drinking frequencies, amount of food in stomach, when eaten, mints or mouthwash, also affect the breath alcohol readings." Studies have shown that for every 1° change in temperature, the estimated BAC increases by 6.5%. Change in the temperature of the alveolar air from the alveoli to the mouth is of the order of 4°C (31 - 35°C). Therefore the BAC would be shown to be higher by 26% than the actual.

Breathalyzer myths
A 2003 episode of the popular science television show tested a number of methods that supposedly allow a person to fool a breathalyzer test. The methods tested included breath mints, onions, denture cream, mouthwash, pennies and batteries; all of these methods proved ineffective. The show noted that using these items to cover the smell of alcohol may fool a person, but, since they will not actually reduce a person's BAC, there will be no effect on a breathalyzer test.



1. http://medind.nic.in/jal/t09/i3/jalt09i3p291.pdf
2. http://www.chandigarhtrafficpolice.org/drunken.htm
3. http://en.wikipedia.org/wiki/Breathalyzer#Breath_analyzer_myths

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