Gas, CO and Flame Are Other Valuable Types of Detectors
Gas detectors detect toxic gases resulting from combustion (like carbon monoxide) and flammable gases capable of combustion (like propane and butane). These detectors are designed to detect the presence of gases before they reach fatal or explosive levels. Depending on the application, gas detectors may sound a local alarm, activate a general alarm, shutdown the gas source, or turn on ventilation equipment.
Carbon monoxide (CO) is a colorless, odorless and tasteless gas that can be fatal with extended exposure. CO depletes the amount of oxygen in the air, and when inhaled, it binds to blood cells and prevents them from carrying oxygen throughout the body. CO detectors are becoming very popular in residential applications, and are even being required by some local codes. Fireplaces, wood stoves, gas heating appliances and automobiles can produce carbon monoxide. CO detectors are typically wall mounted at 5 feet above the floor.
Cooking and heating gases (methane, propane, etc.) present an explosion concern if they reach sufficient levels. Combustible gas detectors are designed to detect these gases in concentrations well below their lower explosive limits. The mounting height of the detector depends on the type of gas being detected. Lighter-than-air gases (such as methane) require the detector to be mounted close to the ceiling. Heavier-than-air gases (such as propane) require the detector to be mounted close to the floor.
Flame detectors respond to visible or invisible light produced by a fire. Flame detectors are extremely sensitive (they can see glowing embers) and are extremely fast responding. Due to their high sensitivity and rapid response, they are typically used in hazardous areas like fuel areas, jet hangers and any other places a small flame or ember could quickly result in an explosion or rapid fire. Flame detectors are available in infrared (IR), ultraviolet (UV) and combination IR/UV. The actual detector type used depends on the environment and the type of flame or ember to be detected.
Follow Code to Ensure the Highest Level of Life Safety From Fires
Spacing of automatic detectors is covered in NFPA 72, Chapter 5. Many factors can affect the permitted spacing of automatic detectors, such as the ceiling height and ceiling support structure, which are critical. A high ceiling allows heat and smoke to cool and stratify before it reaches the ceiling, which could result in a significant detection delay during a fire.
Ceiling support structures such as beams and joists can also delay automatic detectors’ detection of a fire. If heat or smoke must fill up and overflow several troughs created by beams and joists before reaching the detector, detection may be delayed. If the air cools or the smoke dissipates, or if stratification occurs, detection may not even occur at all until it is too late.
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