Location - Carbon Monoxide Detector

[LSaupe]

I am installing a Carbon Monoxide Detector and have heard differing views on where to mount this. Some tell me to mount it near the floor (as CO sinks), others say with a wood stove mount it high as the CO will travel with the bouyant air.

What makes the best sense here?

Larry S.

 

[BrotherBart]

Either way. CO is so near air in density and mixes so well with it that it makes no difference.

Now I will sit back with a Friday night adult beverage and watch those that disagree go at it, or me. :coolgrin:

 

[RPK1]

I am installing a Carbon Monoxide Detector and have heard differing views on where to mount this. Some tell me to mount it near the floor (as CO sinks), others say with a wood stove mount it high as the CO will travel with the bouyant air.

What makes the best sense here?

Larry S.

It doesn't really matter. Make sure you have at least one in the vicinity of the bedroom(s). Also know that all CO and smoke detectors should be replaced every five years or so.

RPK1

 

[WidowMaker]

from the First Alert web site...

Carbon Monoxide Detectors - UL Standard

"According to UL Standard 2034, home carbon monoxide detectors must sound a warning before carbon monoxide levels reach 100 parts per million over 90 minutes, 200 parts per million over 35 minutes or 400 parts per million over 15 minutes. The standard requires the alarm must sound before an average, heathy adult begins to experience symptoms of carbon monoxide poisoning. The warning provides time to evacuate the premises."

PLACEMENT OF CARBON MONOXIDE DETECTORS IMPORTANT

Proper placement of a carbon monoxide detector is important. If you are installing only one carbon monoxide detector, the Consumer Product Safety Commission (CPSC) recommends it be located near the sleeping area, where it can wake you if you are asleep. Additional detectors on every level and in every bedroom of a home provides extra protection.

Homeowners should remember not to install carbon monoxide detectors directly above or beside fuel-burning appliances, as appliances may emit a small amount of carbon monoxide upon start-up. A detector should not be placed within fifteen feet of heating or cooking appliances or in or near very humid areas such as bathrooms.

When considering where to place a carbon monoxide detector, keep in mind that although carbon monoxide is roughly the same weight as air (carbon monoxide's specific gravity is 0.9657, as stated by the EPA; the National Resource Council lists the specific gravity of air as one), it may be contained in warm air coming from combustion appliances such as home heating equipment. If this is the case, carbon monoxide will rise with the warmer air.

For this reason, the makers of First Alert (R), the leading brand in carbon monoxide detector technology, suggests mounting the detector on the ceiling. This also puts the detector out of the way of potential interference, such as pets or curious children

 

[Detector$]

Ultimately NFPA 720 - 'Standard for the Installation of Carbon Monxide (CO) Warning Equipment in Dwelling Units' code takes precedence.

 

[fossil]

Ultimately NFPA 720 - 'Standard for the Installation of Carbon Monxide (CO) Warning Equipment in Dwelling Units' code takes precedence.

OK. And it sez...what, exactly? Rick

 

[Detector$]

Sorry for the delay... I just read a great report from the NFPA research foundation, the University of Maryland, and some prominent consulting engineers.
In short, the CO will generally rise or follow the air path. The best places to locate the detectors are at the highest unobstructed point on the ceiling above the fuel burning appliance or on the ceiling a few feet from your return air register. Your HVAC system will distribute the CO to other parts of the house.

From the NFPA report:

"CO detectors should be sited proximate to the combustion device with the detector located high in the space containing the combustion device. Pre-stratification effects of heat sources high in the space or by heated roof decks should be considered. Where such effects could prevent operation of the CO detector, placement of the CO detector at around nose height or at the height of openings to other spaces may be indicated. For substantial CO sources, detectors placed at or near the floor may result in detection delays of concern with respect to potential prealarm CO exposures. CO detectors should be sited throughout the occupied portions of a building. These detectors should be located in relatively open areas. Where HVAC systems are in continuous use, the ventilation rates will stir the HVAC zone to create fairly uniform CO concentrations. In these circumstances, location of one CO detector per HVAC zone is indicated. However, some buildings do not use HVAC systems or the operation of HVAC systems is limited to seasons and times when heating or cooling is called for by a thermostat. Buoyancy and other secondary flow mechanisms are generally effective in mixing openly connected rooms on a single floor. Closed doors are effective in limiting CO dispersion such that placement of a CO
detector behind a closed door will not provide effective protection. Flow of CO to floors below the floor of origin cannot be relied upon to operate CO detectors. However, upward flow of CO to a second floor is relatively effective when the two levels are openly connected. Based upon these findings, CO detectors should be located on every floor and detectors should be provided in each area of a floor defined by normally closed doors. Where an HVAC system is present, at least one CO detector per HVAC zone should be provided. Where HVAC operation is continuous, relaxation of CO detector siting requirements with respect to floor and area defined by closed doors can be allowed."

Fireplaces and stoves are notably efficient producers of CO and produce the following amounts of CO based on normal operating conditions:
Residential Fireplaces: 126.3 g/kg of fuels (wood)
Residential Wood Stoves: 26-161 g/kg of fuels (wood)
(Wood burning appliances typically produce CO at a rate of 1.4 to 8.7 mg/s per kW of nominal (heat energy) input and generally produce CO at rates up to 100 mg/s)

and...

"While wood burning appliances are also serious CO sources, the emissions are less likely to be insidious due to other irritating and
odorous constituents of the combustion products."

 

[LSaupe]

Great stuff. Thanks for posting.

 

[firefighterjake]

I am installing a Carbon Monoxide Detector and have heard differing views on where to mount this. Some tell me to mount it near the floor (as CO sinks), others say with a wood stove mount it high as the CO will travel with the bouyant air.

What makes the best sense here?

Larry S.

It doesn't really matter. Make sure you have at least one in the vicinity of the bedroom(s). Also know that all CO and smoke detectors should be replaced every five years or so.

RPK1

RPK1 -- Not bad advice . . . but a bit of an over-kill in regard to the smoke detectors. Presently, CO detectors should be replaced every 5 years and smoke detectors should be replaced every 10 years -- of course changing them out earlier rather than later certainly isn't a bad thing.

In reference to the original question . . . I've always gone with the "doesn't matter too much" philosophy in regards to height placement. As mentioned CO will rise on warmer air so placing it higher on a ceiling or wall relatively close to the most likely source of CO would in theory give a faster alarm rate. That said, unlike a fire where the smoke produced in a fire can kill a person very quickly, most CO poisonings are typically caused over a much longer term (with some notable exceptions -- i.e. person running a generator inside their basement, running a car inside an enclosed garage, etc.) which for me means the commonsense factor must come into play -- namely being if I was to only have one CO detector I would either place it in the hall outside the bedrooms (since for 6-8 hours most folks are asleep) or in an area close (but not too close) to the most likely CO source(s).

In my own case I have a cheap AC powered CO detector (so with no outlets on the ceiling I don't have a lot of choice on height placement) . . . I have opted to place it in the kitchen (propane stove) which is next to my Utility Room (propane hot water, oil boiler).

As for the rest of folks' advice . . . all very good and very valid.