If you're the type to leave your car running when it's cold out -- take note.On Monday night, the Denver City Council passed an amendment to the idling ordinance which makes it illegal to leave your car running for longer than five minutes at a time, even if youre sitting in it."It's really unnecessary to leave your car running any longer than five minutes at a time," said Janet Burgesser, an environmental health analyst for the Denver Department of Health.There is one primary exemption. If the temperature drops below 20 degrees, then the ordinance is not enforced.Cab driver Gamel Massanou sees the ordinance as a potential problem."If it's cold, I keep the car on so it'll stay warm. Customers do not want to get into a cold cab," said Massanou.The ordinance is actually an amendment to an ordinance that was already on the books."It was illegal to idle a vehicle for longer than 10 minutes in any one hour time period. We've reduced that to five minutes," said Burgesser.That's news to Sarah Hargrave."I was not aware of that," said Hargrave.She just moved here from North Dakota, where she said everyone leaves their car running."You go to the grocery store, and probably half the cars in the parking lot are running while people are in getting groceries."Emergency vehicles are exempt from the ordinance."Where's the crackdown necessary?" asked 7NEWS reporter Russell Haythorn. "Mainly in areas where there are a lot of deliveries, like downtown," said Burgesser.FedEx driver Dan Williamson said his company already has a no idling policy."If you're not in the seat, your truck's not supposed to be running," said Williamson. Massanou wonders if it's really necessary."(Leaving your car running) is normal for everybody," he said.Enforcement will be complaint-driven. Warnings will likely be issued on a first offense. Fines after that can reach $2,000 per violation.This ordinance is different than the puffing ordinance. Puffing applies when the car is running and no one is inside. Its main objective is to reduce auto theft.This idling ordinance applies even if you're sitting in your car. Its main objective is to reduce pollution and improve public health.