Are you a puffer? It's not hard to be a puffer. All you have to do is leave your car running while you are in the house or when you run into a store.

Police say the danger of puffing, especially at a convenience store, could be lurking around the corner as a thief will wait for you to do it and that’s when they jump in your car and take off.

Colorado state law requires vehicles to be turned off if left unattended for any period of time. Police are teaming up again with the Colorado Auto Theft Investigators group in trying to educate the public that leaving a vehicle on and unattended is a good way to get it stolen. A special crackdown will start on Dec. 14 as police in many cities and counties will be looking for violators during Puffer Week 2009.

Colorado doesn't track puffer thefts, but it’s estimated that almost half of all auto thefts occur because the keys are left in the vehicle. Aurora police say that on average nearly two dozen puffer vehicles a month are stolen in the cold-weather months of December, January and February.

The fine for puffing varies from city to city. The fine in Denver is $25. The fine in Aurora starts at $75.