Indoor burning frequently requested information

Burning restrictions apply November-March.

Stoves that are exempt from burning restrictions

  • Environmental Protection Agency (EPA)-certified Phase III stoves or inserts.
  • Colorado-approved pellet stoves or inserts.
  • Colorado-approved masonry heaters.
For a list of approved devices, see the approved indoor burning devices page.

Where burning restrictions apply

  • Pollution Action Day restrictions generally apply to seven counties in metro Denver:
    • Denver.
    • Boulder.
    • Broomfield.
    • Douglas.
    • Jefferson.
    • Adams and Arapahoe counties west of Kiowa Creek.
Homes above 7,000 feet in elevation are exempt from the restrictions.

Fuel type doesn’t matter

All wood burning appliances (even if certified) may only burn clean, dry, untreated wood. Materials that shall not be burned include: whole tree stumps (must be chipped), tires, chemicals, plastic, construction debris, and trash.

All wood-burning appliances (e.g. stoves, fireplaces, masonry heaters, fire pits, furnaces, boilers) are subject to 20% opacity requirements if fuel is not clean, dry wood or if the use is for commercial purposes

Uncertified stoves, heaters or conventional fireplaces, regardless of the type of fuel, must not be operated on air quality Action Days in the restricted area.

Approved pellet stoves are exempt

Check the list of approved pellet stoves to see if yours is exempt:

If your stove is your sole source of heat

If you rely on a wood stove as your only source of heat, you should contact your local health department or building department about an exemption from burning restrictions. Most municipalities in the seven-county metro Denver area have their own ordinances and regulations that include provisions for exemptions.

No exemptions for individual stoves

Individual stoves can’t be tested for emissions. The EPA-approved testing must be conducted at an appropriate laboratory. It’s done for an entire model line and is quite expensive.

Reporting violations

Call the 24-hour indoor burning hotline:
If the state has jurisdiction, we’ll contact the suspected violator. If a local municipality has jurisdiction, we’ll pass along the information you report and the local government will follow up on the complaint.


Most local municipalities in the restricted area enforce indoor burning bans on air quality Action Days through local ordinances. The Air Pollution Control Division has enforcement jurisdiction only in areas without local ordinances.

For areas under state regulation:

  • After an alleged violation is reported, the division contacts the party involved to inform them of the regulations, limitations, and requirements to encourage compliance.
  • If the party allegedly responsible does not voluntarily comply, the division begins an investigation.
  • If investigators find a violation of state regulations, the division may pursue formal enforcement initiated with a notification of the violation and an enforcement conference between the responsible party and state regulators
  • Formal enforcement is typically resolved with one of three settlement options: 
    1. If it is determined that no violation occurred, then the case is closed out with a no-further action letter
    2. If it is determined that a violation occurred, then the division calculates a civil penalty and offers to resolve the case with a Compliance Order on Consent to ensure future compliance
    3. If the alleged violation cannot be resolved through the typical settlement process, then the division may issue a Compliance Order with compliance requirements and a penalty
  • State statute allows the division to assess civil penalties up to $15,000 per day per violation

New installations in metro Denver

Any indoor burning device you buy or install in the seven-county metro Denver area must meet current emissions standards. The 7,000-foot elevation exemption applies only to the use of indoor burning devices, not their sale or installation.

“Clean” burning non-EPA Phase III stoves

If it can be demonstrated by valid manufacturer testing data that your non-EPA Phase III stove is "cleaner" than EPA Phase III standards, then you can install and use it on Action Days.

EPA Phase III standards

The previous usage of the term "Phase II" regarding wood stoves in Colorado has now been superseded by the term "Phase III".

Regulation No. 4 defines an EPA Phase III Certified wood-burning stove as that which meets the emission standards set forth in Section II.A.  

Part 3 of that section states  "(State Only) On or after May 15, 2020, no person shall advertise to sell, offer to sell, sell, or install a new wood-burning stove in Colorado unless it meets the emission standards set forth in 40 CFR Part 60, Section 60.532(b) or (c) (2015)."

Therefore, the current requirements of Reg. 4 for wood burning stoves is in direct accordance with current EPA Phase III guidelines.

Stoves on the "exempt from certification list"

Contact your local municipality to get an exemption letter or to report a violation.

Selling a used, uncertified wood stove

You’re not allowed to sell a used, uncertified stove in the seven-county metro Denver area, but you can sell it elsewhere in Colorado.

Conventional masonry fireplaces

You can use a conventional masonry fireplace on Action Days only if it's equipped with gas logs, an EPA Phase III insert, an approved pellet insert or an electric device, and if state or local ordinances don’t prohibit it.

Approved pellet stoves

Although many pellet stoves burn "cleanly," we approve only those whose manufacturers have performed the required testing and submitted the appropriate paperwork to us certifying that the pellet stove emits less than 4.1 grams per hour of particulates.

How to tell if it’s an Action Day

To determine if it is an air quality Action Day and for more information, please visit our air quality website.

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Wood-fired boilers

Smoke from outdoor wood-fired boilers can be a serious health issue and can violate state regulations. Learn more about Choosing the Right Hydronic Heater from the EPA. Wood-fired boilers are located outside in small shed-like structures. The hot water produced by the fire is circulated indoors and used in heating.