It’s time for an early public service announcement, well before St. Patrick’s Day celebrations begin this weekend.

The American Chemical Society is out with a video about the inner workings of a breathalyzer — and why you can’t trick it.

“If you think you can beat a breathalyzer, think again; chemistry will land you in cuffs,” the organization said.

In it, an officer from Maryland explains how the sensor in a breathalyzer reacts with alcohol, putting out a reading based on how much alcohol was in the air. These devices are calibrated to the legal limit of .08 as well, which the American Chemical Society said should ensure that it’s measuring breath samples accurately.

“So drink your green beer, have a good time, but remember the bottom line: bring a designated driver who will blow one of these …”

Image source: YouTube

Image source: YouTube

“… so you don’t end up in one of these.”

Image source: YouTube

Image source: YouTube

Watch the video to learn more:

The video went on to explain that once at a police department, an even more sensitive device is often used to measure a suspect’s blood alcohol level.

According to the National Highway Transportation Safety Commission, two out of five deaths in crashes between 2006 and 2010 involved a drunk driver during St. Patrick’s Day celebrations. Of those, 80 percent of St. Patrick’s Day drunk driving deaths in 2010 involved drivers with blood alcohol levels nearly twice the legal limit.