There’s a myth that 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.” Why CO alarms are often installed near the floor Standalone carbon monoxide alarms are often placed low on the wall because they need to be plugged into an outlet that’s near the floor. CO alarms can also have a screen that
shows the CO level and needs to be at a height where it’s easy to read. Why you shouldn’t install a CO alarm near heating or cooking appliances 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. For more information about carbon monoxide safety, visit the National Fire Protection Association. Was this helpful? How can we improve it?
► What should the mounting height of the sensors be?
The sensor mounting height depends the type of application and on the density of the target gas relative to air. Heavier than air gases should typically be detected 6 inches from the floor, lighter than air gas sensors should typically be placed on or near the ceiling, and gases which have a density close to that of air should have sensors installed in the "breathing zone" 4 - 6 ft (1.2 - 1.8 m) from the floor. The breathing zone refers to the area 4 - 6 ft (1.2 - 1.8m) from the floor, where most human breathing takes place. This is a good default location for sensors, as many gases often disperse well in air.
Sensors should be placed near the source of the gas if possible. For example, near the compressor or piping.
Sensors should not be placed near ventilation fans or openings to outside. They should be placed in areas where there is good air circulation, but not in the path of rapidly moving air. Pay particular attention to "dead air spots" where there is little or no air movement.
Consideration should be given to accessibility for calibration when locating sensors. For example, a sensor mounted 30 feet (9 m) off the floor will be difficult or even hazardous to service.
Some applications may require the sensor to be mounted at a different height than indicated below. If you have any questions, please ask your Regional Sales Manager or our Technical Service Department.
Gas detectors should be mounted upright on a vertical surface like a wall, column or beam - do not mount upside down, sideways or flat on the floor.
Typical Mounting Heights for Common Gases
On or Near the Ceiling:
• Ammonia (NH3)
• Hydrogen
(H2)
• Methane (CH4)
Breathing Zone (4 - 6 ft / 1.2 - 1.8 m above floor):
• Acetylene (C2H2)
• Carbon Dioxide (CO2)
• Carbon Monoxide (CO)
• Ethylene (C2H4)
• Formaldehyde (CH2O)
• Oxygen (O2)
• Nitric Oxide
(NO)
• Nitrogen Dioxide (NO2)
• Phosphine (PH3)
• Silane (SiH4)
• Hydrogen Sulphide (H2S) (3 ft above floor)
Near the Floor (6 in / 15 cm above floor):
• Acetone (C3H6O)
• Alcohols
• Benzene (C6H6)
•
Butane (C4H10)
• Chlorine (Cl2)
• Diesel Fuel
• Ethanol or Dimethyl Ether (C2H6O)
• Fluorine (F2)
• Gasoline
• Hydrogen Fluoride (HF)
• Hexane (C6H14)
• Isobutane (C4H10)
• Isobutylene
(C4H8)
• Isopropyl alcohol (C3H8O)
• Jet Fuel
• Methanol (CH4O)
• Ozone (O3)
• Propane (C3H8)
• Pentane (C5H12)
• Propylene / Propene (C3H6)
• Sulphur Dioxide
(SO2)
• Toluene (C7H8)
• TVOC (target gas dependant)
• Xylene (C8H10)
Near the Floor (12 in / 30 cm above floor):
• Hydrogen Chloride (HCl)
• Hydrogen Cyanide (HCN)
• Refrigerants
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