The alert sitting over metro Denver this afternoon is about ozone, not smoke. CDPHE and the Regional Air Quality Council issued an Ozone Action Day Alert at 4 p.m. Monday, August 17, for the Front Range Urban Corridor from Douglas County north through Larimer and Weld. Nobody is burning firewood in August. But the machinery throwing that alert is the same machinery that starts restricting your fireplace in about ten weeks, and this fortnight NOAA gave Front Range homeowners a reason to watch the calendar.
Today the Action Day is about ozone. On November 1 it starts being about your fireplace.
The current alert, posted on the state's Front Range air quality advisory page, blames "a decreasing threat for showers and thunderstorms along with very warm temperatures" for pushing ozone into the Unhealthy for Sensitive Groups category Monday and Tuesday. Here is the part worth filing away. An Action Day is one mechanism that changes what it restricts depending on the season:
"For example, during the summer open burning is prohibited when an Action Day for ozone and/or fine particulates is in effect. During the winter, residential burning restrictions are in effect when an Action Day for Visibility is in effect." CDPHE Air Pollution Control Division
The winter high pollution season runs November through March. Per CDPHE's indoor burning restrictions page, when an Action Day is called in that window, indoor burning is restricted across seven metro counties: Denver, Boulder, Broomfield, Douglas, Jefferson, and the parts of Adams and Arapahoe west of Kiowa Creek.
What most homeowners get wrong is assuming the restriction is absolute. It is not. Your device is exempt if any one of these is true:
- It is a Phase II EPA-certified stove, an EPA-certified pellet stove, or a Colorado-approved masonry heater.
- It sits above 7,000 feet.
- It is not certified, but indoor burning is your primary heat source and you hold an exemption letter from the state or your local jurisdiction.
An open masonry fireplace is not on that list. Burn in one on a restricted day in those seven counties and you are out of compliance. Sort out where you stand in the two months before November, not on the first cold Saturday. Details are on our Colorado chimney laws and regulations page.
NOAA now puts a historic El Nino at better than two in three
The Climate Prediction Center issued its monthly ENSO Diagnostic Discussion on August 13, and moved the numbers up again. The status is an El Nino Advisory, with a greater than 90 percent chance of a very strong event through fall and winter 2026-27. Then the CPC said something it does not say often:
"During the October-December 2026 season, there is a 69% chance of a historic event that would exceed the strength of previous El Niño events dating back to 1950 (+2.5°C or more for a 3-month RONI value)." NOAA Climate Prediction Center, August 13, 2026
Straight talk about what that does and does not tell you: it does not tell you Denver gets buried. The CPC attaches its own caution, noting that with an event this size the odds of El Nino-consistent impacts are larger "but they are not guaranteed." Colorado sits in an awkward spot for ENSO signals, and anyone selling you a confident Front Range snow total in August is guessing.
What is not a guess is freeze-thaw. Water gets into masonry during the warm part of the day and expands when it refreezes overnight, and our swing from a 55 degree afternoon to a 20 degree night does more damage than raw cold ever does. A wetter winter loads the dice, because moisture is what turns a hairline crown crack into a spalled chimney by March. The points of failure:
- The crown and the cap. These take the water first, and a missing or rusted-out cap sends rain and snowmelt straight down the flue. See chimney cap repair and installation.
- Mortar joints and brick face. Cracks found in September are cheap. Cracks found in February are not.
- Draft. Cold, dense air sitting in an exterior flue makes a chimney hard to start and prone to backpuffing into the room on the first burn.
The next ENSO discussion lands September 10, but do not wait for it. Book a chimney inspection in Denver while the weather is still boring, because the calls we cannot get to fast are the ones that come during the first upslope storm.
Your Xcel bill is changing this month, and the flue you ignore is part of that math
Xcel's electric rate case, Proceeding No. 25AL-0494E, is at the decision point right now. Per the Colorado Public Utilities Commission, Xcel filed on November 21, 2025 seeking a $356 million annual revenue increase, which the PUC pegs at roughly 9.9 percent for the average residential customer, about $9.94 a month, starting late August 2026.
A non-unanimous settlement backed by the company, PUC staff and several intervenors would cut that to $225 million, or about 5.86 percent and $6.13 a month. AARP, the Colorado Office of Utility Consumer Advocate and the City of Boulder oppose it. A final decision is expected in Q3 2026, with rates implemented this month if approved.
So the range on the table is roughly six to ten dollars a month more, arriving right as heating season starts. Not catastrophic, and we will not pretend it is. But it changes the return on efficiency work you were already putting off. Two things move the needle on a hearth:
- A gas insert converts an open fireplace, which is usually a net heat loser, into something that produces usable heat. That is the difference between a fireplace that costs you money to run and one that offsets the furnace. See gas fireplace inserts in Colorado.
- Creosote and a restricted flue make a wood appliance burn cooler and dirtier, so you get less heat per cord. A chimney sweep and cleaning is the cheapest efficiency work available.
Two federal actions on the alarms that are supposed to catch a chimney problem
Your CO alarm is the last line of defense on a blocked flue, a cracked heat exchanger, or a gas appliance venting badly. Two CPSC actions this summer say the cheap ones are not reliably doing that job.
On June 25, 2026, the CPSC announced recall 26-582 on Treatlife combination smoke and CO detectors sold on Amazon from November 2025 through April 2026 for about $40. They can fail to alert to a fire. It is a small recall, about 20 units, no incidents reported.
The bigger one is warning 26-614, issued July 9, 2026, on JNHCD combination smoke and CO detectors sold on Amazon, eBay and Sears. The CPSC says the seller has been unresponsive to requests for a recall, which is why this is a warning and not a recall: no refund is coming. The buying guidance is the line to keep:
"Consumers should only buy smoke alarms and CO detectors that meet the UL 2034 and UL 217 safety standards." U.S. Consumer Product Safety Commission, July 9, 2026
Turn your alarm over and look for those standards on the back. If it is an off-brand marketplace unit, replace it before you light anything this fall. An alarm that does not alarm is worse than no alarm, because you stopped worrying.
What we would do before the next edition
- Check the back of every smoke and CO alarm in the house for UL 217 and UL 2034. Replace anything off-brand or undated.
- Find out whether your wood-burning device is on the exempt list before November 1, especially if you are in the seven metro counties.
- Get eyes on the crown and cap now, while a small crack is still a small bill.
- Book the inspection now. October and November availability goes fast, and faster in a winter people are nervous about.
- If your open fireplace costs you money to run, price an insert while there is still time to install before the first hard freeze.
If you want a straight answer about your chimney rather than a sales pitch, get in touch or call (720) 207-9232. We will tell you if you do not need the work.
The Flue Report is published every two weeks by Adam Chimney Sweep, serving Denver and the Colorado Front Range. Edition 5 lands the week of August 31, 2026.
