Common problem · Right now

CO alarm going off?

Treat it as real. Carbon monoxide is invisible and odorless, and a furnace with a cracked heat exchanger is the most common source in a Denver home.

$99 diagnostic, credited to the repair
Same-day across Denver
No overtime fees

Get Help Fast (720) 447-0177

How urgent

Get everyone outside first. Then call from outside.

Call if: The alarm sounds at all
Call if: Anyone has flu-like symptoms that improve outside
Call if: You see soot around the furnace or water heater

(720) 447-0177

What it usually is

The causes, most common first.

1

Cracked heat exchanger

Combustion gases leak into the air stream. The furnace must be replaced.

Replacement; we show you the crack
2

Blocked flue or vent

Snow, a bird nest, or a collapsed liner pushes exhaust back into the house.

Clear the flue, repair the liner
3

Water heater backdrafting

A tight house or a strong exhaust fan pulls flue gas back down.

Fix the draft, test every appliance

Every fix gets a written price before any work. The $99 diagnostic is credited toward it.

Try this first

What to check before you call.

If one of these fixes it, great. If not, you’ve saved us five minutes on the diagnosis.

1
Get everyone, including pets, outside into fresh air.
2
If anyone is dizzy, nauseous, or confused, call 911.
3
Don’t go back in to open windows.
4
Call us from outside. We test every appliance before anyone returns.

Who we are

Hello. We’re Duality.

Duality Heating and Air LLC is a Denver heating and cooling company run by one licensed technician and the people he trusts. We fix furnaces, ACs, heat pumps, and the air in your home, and we do it the way we’d want it done at our own house. Comfort, in perfect balance.

Denver-based

One technician who lives here, not a call center in another state.
Price in writing

You approve the number before we touch a tool. It never changes.
Fix before replace

We repair what can be repaired and show you both numbers when it can’t.

Questions

Carbon Monoxide Alarm, answered.

The alarm stopped. Do I still need a visit?

Yes. CO levels fall when the furnace cycles off. The source is still there.

From Denver neighbors

HVAC service

Cecilia Gomez
Google review

“Professional, knowledgeable, and incredibly helpful. He took the time to explain everything clearly, answered all of my questions, and made the entire process easy and stress-free. I truly appreciated his honesty, responsiveness, and attention to detail.”
AC repair

Jessica Russman
Google review

“Very honest and reliable. He showed up on time and fixed our old AC after we had several companies try to sell us a new one. We would 1000% recommend Duality to anyone who wants to feel confident they’re dealing with the right company.”

Same-day help