The Colorado puffer law makes it illegal to leave a vehicle running and unlocked while it sits unattended, even on a freezing morning while you finish getting ready inside. The rule lives at Colorado Revised Statutes Section 42-4-1206, and breaking it is a class B traffic infraction with a fine between $15 and $100.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions A 2016 amendment added exceptions for remote starters and other security measures, so warming up your car legally is possible. You just have to do it in one of a few specific ways.
What the Law Actually Prohibits
The statute targets a narrow scenario: leaving an unlocked motor vehicle unattended without stopping the engine, locking the ignition, removing the key, and setting the brake. The word “unlocked” is doing most of the work. A locked, idling car sits outside the prohibition, though how you got it locked and idling matters, and that’s where the exceptions come in.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions
The rule applies to anyone “driving or in charge of” a vehicle, not just the registered owner. Borrow a friend’s car, leave it running with the doors unlocked while you run into a store, and you’re the one who gets the ticket.
The Fine
A puffer law violation is a class B traffic infraction. Under Colorado’s penalty schedule, that carries a minimum fine of $15 and a maximum of $100, plus a small surcharge.2FindLaw. Colorado Code 42-4-1701 There is no separate escalation for repeat offenders written into the puffer statute itself.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions
The fine is modest. The stolen car that often follows is not, which is the real reason to pay attention.
How To Warm Up Your Car Legally
The 2016 amendment (HB16-1122) created two categories of legal ways to leave your car idling: use a remote starter system, or use “adequate security measures.”3Colorado General Assembly. HB16-1122 Remote Starter Systems
Remote Starter Systems
A remote starter is a device installed in the vehicle that lets you start the engine by remote or radio control. If you use one, you comply with the law, but you still need to keep the keyless start fob far enough from the vehicle that no one inside could put it in gear and drive off.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions The car warms up; a thief who breaks in still can’t move it.
Adequate Security Measures
Even without a remote starter, you can comply by using an adequate security measure. The statute lists three examples, and says the list is not exhaustive:
- Using a vehicle that requires a physical key to put it in gear, even with the engine already running.
- Keeping a keyless start fob out of proximity of the vehicle so it can’t be driven.
- Using a steering wheel lock like a club-style device.
The “includes, but is not limited to” language means other reasonable measures could qualify, though the statute doesn’t say what else would count.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions
Stay With the Car
The law only reaches unattended vehicles. If you’re sitting in the driver’s seat while it warms up, there’s no violation. Scraping the windshield next to the running car is a grayer area, but the further you get from the vehicle, the closer you are to the statute’s target.
There Is No Cold Weather Exception
This is where drivers get caught. Colorado winters are harsh, and warming up an unlocked car in the driveway feels like ordinary morning routine. The puffer law contains no exception for cold weather, defrosting, or any temperature threshold. Negative 20 outside is legally the same as 60. The only ways to warm up your car unattended are the remote start and adequate security options above.
The Colorado State Patrol has warned drivers directly about this, noting that puffing is illegal and that cold-weather vehicle theft is a persistent problem across the state.4Colorado State Patrol. Cold Weather Habits May Leave You at Risk for Motor Vehicle Theft
What Happens If Your Idling Car Gets Stolen
The ticket is the smallest part of the risk. If someone drives off with your running car, two questions come next.
Your Insurance Claim
Most comprehensive auto policies cover theft, but they also typically require the policyholder to take reasonable precautions. Leaving a car running and unlocked with the key in the ignition is the kind of fact pattern an insurer can point to as a failure to mitigate risk. Whether that leads to a denied claim depends on the specific policy language and the insurer. At a minimum, expect more scrutiny and a slower process.
Liability If the Thief Crashes the Car
A common worry is that if the thief causes an accident, the owner of the idling car is on the hook for the damages. Colorado case law generally points the other way. Colorado courts have treated the actions of a car thief as an independent intervening cause that breaks the chain of liability back to the vehicle owner, meaning the thief’s decision to steal and crash the car is treated as the legal cause of the harm. That principle comes from older cases, and specific facts can always shift the analysis, so it isn’t a defense to plan around. It does mean the nightmare scenario people imagine is not the default legal outcome.