Under the Colorado puffer law, you can’t leave a motor vehicle running and unlocked while it’s unattended. The rule lives in 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 carved out exceptions for remote starters and other security measures, but the exceptions are narrower than most drivers assume.
What the Law Prohibits
The statute targets a specific scenario: leaving an unlocked motor vehicle unattended without stopping the engine, locking the ignition, removing the key, and setting the brake. The “unlocked” qualifier matters. A locked, idling car is already outside the prohibition, though how you got it into that state still matters.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions
The law reaches anyone “driving or in charge of” a vehicle, not just the registered owner. Borrow a friend’s car, warm it up in a parking lot, walk away with the doors unlocked and the key in the ignition, and you’re the one who gets the ticket.
The Fine
Puffing is classified as 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 Claims online that fines “start at $50” are off. The statute sets the range at $15 to $100, with no separate escalation schedule for repeat offenders written into this law.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions
The fine itself is modest. The real financial exposure comes from what tends to follow a puffing violation: a stolen car, a skeptical insurance adjuster, and the aftermath. More on that below.
Legal Ways To Warm Up Your Car
The 2016 amendment (HB16-1122) added two categories of exceptions that allow a vehicle to idle unattended without violating the law: using a remote starter system, or employing 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 have to keep the keyless fob far enough from the vehicle that nobody can put it in gear and drive off.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions The idea is simple: the car can warm up, but a thief who gets inside still can’t move it.
Adequate Security Measures
Without a remote starter, you can still comply by using what the statute calls “adequate security measures.” The law lists three examples, and the list is not exhaustive:
- Using a vehicle that requires a physical key to put it into gear, even if the engine is running.
- Keeping a keyless start fob out of proximity of the vehicle so it cannot be driven.
- Using a steering wheel security device like a club-style lock.
The phrase “includes, but is not limited to” means other reasonable security measures could qualify, though the statute doesn’t spell out what else counts.1Justia. Colorado Code 42-4-1206 – Unattended Motor Vehicle – Definitions
Stay With the Car
The statute only reaches unattended vehicles. If you’re sitting in the car while it warms up, there’s no violation. Scraping the windshield from outside the open driver’s door, with the engine running, is the gray area most drivers lose. If you’ve stepped away from the controls and the doors are unlocked, you’re exposed.
There Is No Cold Weather Exception
This is the misconception that gets the most people in trouble. Colorado winters are brutal, and warming up a car before scraping ice feels like common sense. The puffer law contains no exception for cold weather, defrosting, or any temperature threshold. If your vehicle is unlocked with the key in the ignition and nobody is in it, it doesn’t matter if it’s negative 20 outside. The only legal ways to warm up unattended are the remote start and adequate security routes above.
The Colorado State Patrol has specifically warned drivers about the habit, 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 Puffing Car Gets Stolen
The $15 to $100 fine is almost never the real cost of a puffing violation. The real cost comes if the car is gone when you get back outside.
Your Insurance Claim Gets Harder
Most comprehensive auto policies cover theft, but they also typically require you to take reasonable precautions to protect the vehicle. Leaving a car running and unlocked with the key in the ignition is a textbook example of what an insurer might call a failure to mitigate risk. Whether that leads to a denied claim depends on your policy language and the insurer, but it gives the company an argument it wouldn’t otherwise have. At a minimum, expect more scrutiny and a slower claims process.
You Probably Aren’t Liable for What the Thief Does
A persistent myth says that if someone steals your idling car and causes a crash, you’re on the hook for the damages. Colorado case law points the other way. Courts have treated the actions of a car thief as an independent intervening cause that breaks the chain of liability back to the owner. The thief’s decision to steal and crash the car is generally the legal cause of the resulting harm, not your decision to leave the car running. That principle emerged from cases decided decades ago, and specific facts can shift the analysis, so it’s not a defense worth planning around.
One Boundary Worth Knowing
Colorado does have an idling exemption for emergency and public safety vehicles, but it sits in a separate statute (Section 42-14-105) governing diesel-powered commercial vehicle idling standards, not in the unattended vehicle law.5Justia. Colorado Code 42-14-105 – Idling If you’ve seen claims that police cars and ambulances are exempt from the puffer law itself, the legal basis isn’t what’s commonly described.