Carbon Monoxide Detectors: High or Low ?

Wa State CO detector law

The issue of the placement of carbon monoxide detectors is brought up during several home inspections.  Most agents and clients (including 2 firefighters) say that they must be located near the floor as opposed to high up.  All new construction homes have combination smoke/carbon monoxide type detectors that are placed high up at the ceiling.

I contacted Kidde, a major supplier of these detectors. Their response was “In response to your email, carbon monoxide is just slightly lighter in density than air. So it mixes evenly with air. CO detectors can detect CO while located on the ceiling. That is an appropriate location as long as the unit is not in the very corner of a ceiling (in dead air space). Some people think that carbon monoxide is heavier than air, but it is not. Carbon dioxide is heavier than air. Hope this is helpful.”

Nest, another major manufacturer states that “There’s a myth that all carbon monoxide alarms should be installed lower on the wall because carbon monoxide is heavier than air. In fact, carbon monoxide is slightly lighter than air and diffuses evenly throughout the room. According to the carbon monoxide guidelines of the National Fire Protection Association (NFPA 720, 2005 edition), all carbon monoxide alarms “shall be centrally located outside of each separate sleeping area in the immediate vicinity of the bedrooms,” and each alarm “shall be located on the wall, ceiling or other location as specified in the installation instructions that accompany the unit.” Standalone carbon monoxide alarms are often placed low on the wall, but it’s not because they’re more effective at that height. It’s usually because they need to be plugged into an outlet near the floor or have a digital readout that can be easily read. Also keep in mind 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 carbon monoxide detector should not be placed within fifteen feet of heating or cooking appliances or in or near very humid areas such as bathrooms.”

The most common incidents of carbon monoxide poisoning related to cooking inside with charcoal grills and gas fired generators operating in a garage or adjacent to an open window. Another recent type of issue is with keyless ignition systems for cars that can easily be left in the “On” position by accident.  Issaquah CO poisoning

RCW 19.27.530

Carbon monoxide alarms—Requirements—Exemptions—Adoption of rules.

(1) By July 1, 2010, the building code council shall adopt rules requiring that all buildings classified as residential occupancies, as defined in the state building code in chapter 51-54 WAC, but excluding owner-occupied single-family residences legally occupied before July 26, 2009, be equipped with carbon monoxide alarms.
(2)(a) The building code council may phase in the carbon monoxide alarm requirements on a schedule that it determines reasonable, provided that the rules require that by January 1, 2011, all newly constructed buildings classified as residential occupancies will be equipped with carbon monoxide alarms, and all other buildings classified as residential occupancies will be equipped with carbon monoxide alarms by January 1, 2013.
(b) Owner-occupied single-family residences legally occupied before July 26, 2009, are exempt from the requirements of this subsection (2). However, for any owner-occupied single-family residence that is sold on or after July 26, 2009, the seller must equip the residence with carbon monoxide alarms in accordance with the requirements of the state building code before the buyer or any other person may legally occupy the residence following such sale.
(3) The building code council may exempt categories of buildings classified as residential occupancies if it determines that requiring carbon monoxide alarms are unnecessary to protect the health and welfare of the occupants.
(4) The rules adopted by the building code council under this section must (a) consider applicable nationally accepted standards and (b) require that the maintenance of a carbon monoxide alarm in a building where a tenancy exists, including the replacement of batteries, is the responsibility of the tenant, who shall maintain the alarm as specified by the manufacturer.
(5) Real estate brokers licensed under chapter 18.85 RCW shall not be liable in any civil, administrative, or other proceeding for the failure of any seller or other property owner to comply with the requirements of this section or rules adopted by the building code council.