DENVER (CBS4)– Colorado State Troopers are teaming up with law enforcement along the Front Range to warn drivers against warming up their cars this winter.

It’s called “puffing,” when drivers start their car and then leave it running either in the drive way, in a parking lot or at a gas pump. And it’s illegal in Colorado.

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“So whether it’s in a drive way on a road or at a gas station, it’s always critical to remember it’s not only your responsibility but it’s the right thing to do to secure a car before getting away from it,” said Colorado State Patrol Col. James Wolfinbarger.

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Police say it’s easy for thieves to spot vulnerable cars because they have the telltale puff of exhaust coming from the car. It can also lead to more crime.

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“When a car is stolen it leads to a lot of other types of crime. Often times cars are stolen and it gets to a point where they are used for other illegal activity like drug trafficking but also selling and reselling for drug money. So we get into a lot of this where it seems like auto theft on the front but these vehicles that are stolen are used to perpetrate other crimes in other parts of the city or other parts of the state,” said Wolfinbarger.