If a heat detector has a listed spacing of 50 feet, what is its maximum allowable spacing when mounted on an 18′ high ceiling?

In fire alarm system installations, the spacing of heat detectors is crucial for ensuring adequate coverage and response times. The listed spacing of a heat detector typically indicates the distance between detectors under standard conditions, commonly for 10-foot high ceilings. When installing detectors in buildings with higher ceilings, adjustments to the spacing requirements must be made to ensure that the sensitivity and effectiveness of the detectors are not compromised.

For a heat detector with a listed spacing of 50 feet at a standard ceiling height, the general rule of thumb is to reduce the maximum spacing based on the height of the ceiling. In this case, as the ceiling height increases to 18 feet, the maximum allowable spacing for the heat detectors must be calculated.

When applying NFPA (National Fire Protection Association) guidelines or manufacturer's recommendations for spacing adjustments based on ceiling height, an approximate method is to use a factor or a specific formula that considers the height of the ceiling relative to the listed spacing. The spacing is typically reduced by taking into account the specific ceiling height above the standard.

For an 18-foot high ceiling, the maximum allowable spacing often adjusts to approximately 0.7 to 0.8 times the listed spacing. Thus, calculating this using a 50-foot listed spacing gives an approximate maximum spacing