Carbon Monoxide Detector Placement

By
Home Inspector with Jay Markanich Real Estate Inspections, LLC 3380-000723

Carbon monoxide detector placement.

That title surrounds a question I get a lot during home inspections.  And this one -

Is carbon monoxide lighter or heavier than air?

Of course, any time you have gas appliances or a wood-burning fireplace, you should have at least one carbon monoxide (CO) detector in the home.

CO is odorless, tasteless and DOES NOT GIVE WARNING that it is being produced or building up.

And, is it lighter or heavier than air?  Which means, does it rise or fall when produced?

Since the molecular weights of gases differ, what makes them move is convection.  If a gas is released because of combustion, it would tend to rise due to its heat.

CARBON MONOXIDE HAS NEARLY THE DENSITY OF AIR.  CO is slightly lighter.   You can figure this out.  For example:

O=16   C=12   N=14   H=2

You would add things to get the pure density of gasses.

H2 = 1+1 = 2 (very light)
O2 = 16+16 = 32 (slightly heavy)
N2 = 14+14 = 28 (about neutral)
CO2 = 12+16+16 = 44 (heavy)
CO = 12+16 = 28 (about neutral)
H2O = 1+1+16 = 18 (light) - as in humidity or steam

So what is the density of air?  The air we breathe is composed of 80% Nitrogen, 19% Oxygen, .6% inert gases and .4% Carbon Dioxide.

N2 + O2 + CO2 = ?
.8(28) + .196(32) + .004(44) = 28.9 (by definition air is neutral)

So how does CO compare with air?  It is 3% lighter.  So it distributes very easily through a house.

But when CO is produced, it immediately begins mixing, and therefore diluting, with the air around it.  Therefore, it mixes with nitrogen, which doesn't burn, oxygen, which is burned creating the CO, H2O (humidity) and CO2 which are in the air.  So the CO produced is not in pure form in the air.  It is very diluted.  And as CO is produced, it is warmer than the air around it.

So what is the most advantageous place to put a CO detector?  CO moves with the air, so where the air is flowing it will go also.  It is very unpredictable where the air, and therefore CO, will move at any given time.  That is why the instructions with the unit you buy do not say to place it high or low on the wall.

Understanding all that, the National Fire Protection Association (NFPA) suggests in 720, 2-1.1.2* 1998 -

"A carbon monoxide alarm or detector should be centrally located outside of each separated sleeping area in the immediate vicinity of the bedrooms. Where bedrooms are separated and the audibility of the alarm or detector to occupants within the bedroom area could be seriously impaired, more than one unit could be needed. Each alarm or detector should be located on the wall, ceiling, or other location as specified in the installation instructions that accompany the unit."

The suggestion is one that is plugged in and preferably with a battery back up.  These detectors use electrochemical technology to detect CO gas.  Like smoke detectors, they are effective for 10 years.

A local Fire Marshall, my neighbor, told me that the plug-in detectors seem to have a better record for fewer false positives than do the battery-only detectors.  But that is his experience!

My recommendation:  buy a good plug-in detector!  If you want, get one with a battery back up.  Put it near any potential CO source and another near your bedroom(s).  Be sure everyone will hear it.

And you will be safe and feel safe.

Posted by

Jay Markanich Real Estate Inspections, LLC

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560

www.jaymarinspect.com

Greg Large
ERA Real Solutions - Grove City, OH

Thanks for the informative and detailed and timely post on the subject. Think I will add these as Christmas gifts for my kids this year.

Oct 09, 2018 08:14 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Anytime Greg.   And that's a good idea too!

Oct 10, 2018 12:44 AM
Kat Palmiotti
eXp Commercial, Referral Divison - Kalispell, MT
Helping your Montana dreams take root

This is great information to share. I like Greg Large 's suggestion to buy these as gifts!

Oct 10, 2018 03:11 AM
Sham Reddy CRS
Howard Hanna RE Services, Dayton, OH - Dayton, OH
CRS

Thanks for sharing!!!

"A carbon monoxide alarm or detector should be centrally located outside of each separated sleeping area in the immediate vicinity of the bedrooms. Where bedrooms are separated and the audibility of the alarm or detector to occupants within the bedroom area could be seriously impaired, more than one unit could be needed. Each alarm or detector should be located on the wall, ceiling, or other location as specified in the installation instructions that accompany the unit."

Oct 10, 2018 03:40 AM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Kat - they're selling like pancakes!

Thanks Sham.

Oct 10, 2018 07:45 AM
Joe Pryor
The Virtual Real Estate Team - Oklahoma City, OK
REALTOR® - Oklahoma Investment Properties

This is a post worth sharing for all of us. The builders I work with install them in every home.

Oct 10, 2018 03:51 PM
Mike Cooper, Broker VA,WV
Cornerstone Business Group Inc - Winchester, VA
Your Neighborhood Real Estate Sales Pro

Jay, that's a whole lot of valuable information in one post. Thanks for sharing.

Oct 10, 2018 04:49 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

That would be a solid practice, Joe.  And thanks!

Oct 10, 2018 04:50 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Thanks Mike.  And I showed my work, professor!

Oct 10, 2018 04:51 PM
Sajy Mathew
Coldwell Banker Residential Brokerage - Lancaster, PA
Making your real estate dreams become a reality!

Congrats on the feature arcticle and thanks for sharing such important information.  Hoping this helps motivate people to include this item in their home safety features.

Oct 11, 2018 07:08 AM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Thanks Sajy.  Every home with combustible appliances should have CO detectors.

Oct 11, 2018 10:04 AM
Michael Jacobs

Hello Jay --- it's good to know what an expert thinks.  Good information.

Oct 12, 2018 08:45 AM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Thank you, Michael, for that very nice compliment.

Oct 12, 2018 01:29 PM
Kevin Mackessy
Blue Olive Properties, LLC - Highlands Ranch, CO
Dedicated. Qualified. Local.

We usually always do hardwired CO units that last 10 years.  This ensures you don't have the CO detector find its way to a drawer the second it won't stop beeping.

Oct 17, 2018 01:23 PM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Kevin - a lot of those are the combo smoke and CO detectors which aren't recommended because so many of them have been recalled.  The individual CO detectors are fine.

Oct 17, 2018 01:35 PM
Chris Ann Cleland
Long and Foster Real Estate - Gainesville, VA
Associate Broker, Bristow, VA

That reminds me, I have a new one that I bought to plug into the wall with a battery back up, but it's not doing much good still in the packaging on my junk counter.  Better get to unwrapping and plugging that in today.

Oct 30, 2018 07:32 AM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

A lot of work to be sure, Chris Ann, but you can do it!

Oct 30, 2018 12:36 PM
Sally K. & David L. Hanson
EXP Realty 414-525-0563 - Brookfield, WI
WI Real Estate Agents - Luxury - Divorce

Carbon monoxide detectors are now often combined in one device with smoke detectors and legally required on every floor in Wisconsin.

Dec 28, 2018 01:40 AM
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

S&D - you have to be real careful with the combo detectors.  Since 2005 there have been 20 recalls of various brands, for various reasons.  Having proper smoke detectors and separate CO detectors is still very good protection.

Dec 28, 2018 03:05 AM
Paul S. Henderson, REALTOR®, CRS
Fathom Realty Washington LLC - Tacoma, WA
South Puget Sound Washington Agent/Broker!

I can't tell you how many CO detectors I have destroyed and false alarms I have had i through placing it in the wrong position. Thank you for sharing your insight Jay Markanich

Feb 25, 2021 08:47 AM