My home was constructed in 2003 and has a natural gas furnace. Do I need to install carbon monoxide detectors to be up to code? It seems confusing since the first code IRC 315.1 is only for new construction, but the second code IRC 315.3 loops back on .1 for "Existing dwellings" with fuel-burning appliances.

International Residential Code for One- and Two-Family Dwellings 2012

Chapter 3 Building Planning

Section R315 Carbon Monoxide Alarms

R315.1 Carbon monoxide alarms.
For new construction, an approved carbon monoxide alarm shall be installed outside of each separate sleeping area in the immediate vicinity of the bedrooms in dwelling units within which fuel-fired appliances are installed and in dwelling units that have attached garages.

R315.3 Where required in existing dwellings.
Where work requiring a permit occurs in existing dwellings that have attached garages or in existing dwellings within which fuel-fired appliances exist, carbon monoxide alarms shall be provided in accordance with Section R315.1.

  • 1
    If your house was built so recently I assume everything was done to code at the time. Typically you aren't required to add anything later unless you do major wok. Are you asking if the house would be up to code if it were built today? Or do you have a reason to be suspicious of the original builder? Regardless, I agree that you absolutely should have one.
    – Hank
    Jun 6, 2014 at 16:17

2 Answers 2


You should install a carbon monoxide detector regardless of what the code says!


Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect.

The initial symptoms of acute carbon monoxide poisoning include headache, nausea, malaise, and fatigue. These symptoms are often mistaken for a virus such as influenza or other illnesses such as food poisoning or gastroenteritis. ... Increasing exposure produces cardiac abnormalities including fast heart rate, low blood pressure, and cardiac arrhythmia; central nervous system symptoms include delirium, hallucinations, dizziness, unsteady gait, confusion, seizures, central nervous system depression, unconsciousness, respiratory arrest, and death.

Detectors are cheap ($15-$60) and readily available. They come as battery-operated, plug-in, and as combination smoke/CO detectors. I recently replaced the smoke detectors in my house (which were 10 years old and thus at end-of-life) with these combo hardwired units: they are linked, so if one goes off, they all do, and announce "Fire" or "Carbon monoxide".

Bottom line: If you have a fuel-burning appliance (furnace, stove, etc), fireplace, or attached garage, you should have at least one CO detector.

As far as current compliance, the IRC and local building codes typically only apply to new construction or renovation. For example, if you are doing an addition to your house or other type of permit-requiring renovation, you'll have to comply with the building codes for at least that portion. This may vary by jurisdiction, and there may be other specific laws or regulations that require retroactively complying with the codes. I am just a random person on the internet; you should consult with your local permit office and/or building inspector to know for sure.

Your insurance or mortgage company may also have other requirements, on top of local building codes and law.

Law in US

Since July 1, 2009, Colorado requires CO detectors in all new homes and any re-sold homes.

Since Feb 22, 2010, New York state requires at least one CO detector on the lowest story having a sleeping area. Homes built after Jan 1, 2008 must have a hardwired CO alarm.

Since Jan 1, 2011, California requires CO alarms for new homes, and since July 1, 2011 for existing homes.

Law in Canada

In Ontario, homes built after Aug 6, 2011 must have hardwired CO detectors installed. Legislation was passed in Nov 2013 to require CO detectors in all homes with fuel-burning appliances.

  • Doesn't answer my question. What I should do and what is code-compliant are different. I need an interpretation of this code to see if I'm compliant.
    – JMD
    Jun 6, 2014 at 12:54
  • ...August 67th? Jun 9, 2014 at 15:13
  • @ThePopMachine What, you don't have that date where you live? (thanks, fixed)
    – gregmac
    Jun 9, 2014 at 19:59
  • @JMD Updated with a note on applicability. Sorry, I was approaching it thinking of the question as "can I get away without installing a CO detector?" and not "Am I doing everything required to comply with codes?" which I think is what your intention actually was.
    – gregmac
    Jun 9, 2014 at 20:01
  • To be honest I have no intentions. The buyer for my house was asking me about the codes and pointed out these sections, and we couldn't make heads or tails of it. My question was exactly that, a question. I asked it plainly enough.
    – JMD
    Jun 9, 2014 at 20:13

I called the City Inspector and he was able to answer my question:

Number 1 is only for New Construction. This I knew. Number 2 is phrased poorly, but he was able to back up his interpretation to me with legal commentary that happened after the IRC was put into place. He said that all of number 2 ONLY APPLIES if there was work requiring a permit was done.

The code should really be rewritten to be made clear like so:

R315.3 Where required in existing dwellings.
Where work requiring a permit occurs either 
(A) In existing dwellings that have attached garages or 
(B) in existing dwellings within which fuel-fired appliances exist, 
carbon monoxide alarms shall be provided in accordance with Section R315.1.
  • So the question begs, WHY are you asking??? If you are living in the house and have a C of O you need to do nothing. Are you having work done? Did you pull a permit for something new? Jun 9, 2014 at 20:05
  • No, it was just a question.
    – JMD
    Jun 9, 2014 at 20:13
  • 1
    So then the answer is no, you don't need to do anything. Codes are not retroactive to existing structures. But Greg's answer is spot on. Jun 9, 2014 at 20:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.