SALT LAKE CITY (KTVX) — On Friday, Feb. 4, Salt Lake City reached an air quality index score (AQI) of 154, which the state calls “unhealthy.” But what does that score really mean?

According to an online calculator, it means the air pollution you breathed in over a 24-hour period Friday was the same as smoking over three cigarettes.

The online calculator, created by a Github user known as jasminedevv, allows you to plug in the day’s AQI score and multiply it by how many hours you were exposed to it. By using a little math, along with some research from Berkley University, jasminedevv’s tool allows you to get a real-world equivalent of the damage air pollution is doing to your lungs.

## Yeah, but what’s an AQI?

An AQI basically starts by measuring the concentration of air pollution particles floating around in the air. Specifically, they’re measuring for particles smaller than 2.5 microns in size, a measure known as the PM2.5. Once you factor in wind speeds and the temperature outside, you get the AQI (you can get a more detailed explanation from AirNow.gov, if you really want to get into the math).

The AQI runs from 0 to 500, though anything above 300 is considered “hazardous” and would require people to stay inside. The AQI scale can offer insight into who might be most affected by the air pollutants that day.

You can also use the color-coded chart below to see how bad your daily AQI actually is.

## OK, but how does that translate to cigarettes?

The online calculator created by jasminedevv builds on ideas presented by Berkley researchers Richard A. Miller and Elizabeth A. Muller released in 2015. In their study, Miller and Muller calculated the amount of air pollution it takes to equal one cigarette’s worth of smoke.

Now, you should keep in mind — and jasminedevv also warns us — that obviously, different kinds of air pollution have different kinds of effects on different people. Also, various cigarettes have various strengths. The number jasminedevv’s calculator gives is only a guesstimate, so you should take it with a grain of salt.

Still, the calculator can give you at least some real-world examples of what air pollution is doing to our lungs.

## Could you just break that down for me?

According to jasminedevv’s online calculator, an AQI of 64 can translate to one cigarette, an AQI of 108 can equate to two cigarettes, and so on. All figures shown below are for a 24-hour period.

You can view the AQI-to-cigarettes calculator here, and find Berkley’s research here.