What is effect on detection at greater distances?
Since both sensitivity and range are related to fire size, if the detector is placed further away from (or closer to) the fire source, the detectable fire size will vary according to the inverse square law*. So, doubling the detection distance results in only 25% of the radiant energy reaching the detector; or conversely, for the same response time, the surface area of the fire then needs to be 4 times larger! For example, if a standard UV/IR detector, capable of detecting a 1 ft2 (0.1m2) fire at 50 ft (15m), is located at 100 ft (30m) detection distance, the minimum fire then needs to be 4 ft2 (0.4m2). Conversely, at a 15 ft (5m) range, a fire of only 0.1 ft2 (0.01m2) would operate the alarm. *This calculation cannot be used indefinitely. As distance increases, factors such as water vapor, cold CO2 and flame flicker have more impact.
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