Which detector is most apt to give a false fire alarm when monitoring an area where arc welding is taking place?

Which detector is most apt to give a false fire alarm when monitoring an area where arc welding is taking place?

• A. Photoelectric
• B. Ultraviolet
• C. Ionization
• D. Rate of Rise

Answer: (B)

Ultraviolet detectors are designed to sense the UV radiation emitted by flames. Arc welding produces a very intense UV light, so a UV detector can mistake that welding arc for a flame and trigger a false fire alarm—even if there isn’t a real fire. Other detectors respond to different signals and aren’t as easily fooled by welding. Photoelectric detectors rely on smoke particles scattering light, which isn’t the primary signal from a welding arc. Ionization detectors react to ionized combustion gases, which aren’t produced in the same way by welding. Rate-of-rise detectors look for a rapid temperature increase, which welding can cause locally but doesn’t always create the kind of broad, sustained rise these detectors require. So, the UV detector is the most likely to produce a false alarm in an area with arc welding.

Ultraviolet detectors are designed to sense the UV radiation emitted by flames. Arc welding produces a very intense UV light, so a UV detector can mistake that welding arc for a flame and trigger a false fire alarm—even if there isn’t a real fire.

Other detectors respond to different signals and aren’t as easily fooled by welding. Photoelectric detectors rely on smoke particles scattering light, which isn’t the primary signal from a welding arc. Ionization detectors react to ionized combustion gases, which aren’t produced in the same way by welding. Rate-of-rise detectors look for a rapid temperature increase, which welding can cause locally but doesn’t always create the kind of broad, sustained rise these detectors require.

So, the UV detector is the most likely to produce a false alarm in an area with arc welding.