As a big storm rolled into the state this week, law enforcement warned about the risks of leaving a vehicle “puffing,” or idling unattended, as it warms up. This practice is illegal in many parts of the country and can put drivers at-risk of auto theft, as well as contribute to pollution.

On cold and snowy days in metro areas, auto thieves will often travel pairs allowing them to steal vehicles within seconds, relatively unnoticeable to the inattentive passerby. See what this looks like below.

Don’t leave your car puffing outside! It’s generally illegal and puts you at risk to theft. Like the Denver Police Department says, “The cold is miserable, but so is having your car stolen.”

An early report on Monday mentioned that 3 puffing cars had already been stolen in Denver. This didn’t account for the second day of the storm, which hit Denver harder.

Allowing your car to “puff” in Colorado is a Class B Traffic Infraction with a $60 fine.