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Fire Alarms also need to be inclusive
In the event of an emergency relevant notification is mandatory, and should include options to hearing or visually impaired people. That’s where fire alarm strobe lights or combinations of strobe lights and audible devices, such as sirens, horns, and bells, came in place.
The National Fire Protection Association (NFPA) defines codes for the installation of these equipment. The type of notifications required when a fire alarm system is installed in a building (audible, visible, and voice) is driven by the building code, fire code, or life safety code that is adopted in that jurisdiction.
Visible signaling
Strobes installation should follow NFPA 72 Section18.5 and are based on commonly listed candela ratings based on maximum coverage areas. The higher the candela rating of a strobe device, the larger its coverage area.
Candela is the base measurement for describing luminous intensity. It tells you how bright the light source is which shows how far away from an object you can be and while still being able to see it. A simple comparison is that 1 candela is roughly equivalent to the light from a single candle.
A simple comparison is that 1 candela is roughly equivalent to the light from a single candle.
Strobes typically have candela ratings of 15, 30, 75, 94, 95 and 110 cd. While extended coverage strobes typically have candela ratings of 177 and 185 cd.
Compliant visual notification is provided by synchronized flashing strobes (most commonly at 100 (50Hz version) or 120 times a second (60Hz version), as part of either strobe-only visual devices or combination audible/visual devices.
Audible signaling
Loud sirens are part of the fire alarm system. The sound ensures that visually impaired people and those with limited hearing can still detect the need to evacuate.
The Americans with Disabilities Act (ADA) of 1990 establishes several rules for audible fire alarms such as the maximum noise that can’t exceed 120 A-weighted decibels (dbA) and that audible alarms must exceed the noise level in the room by 15dbA. If this causes the noise level to exceed 120dbA, the alarm may be only 5dbA louder, but it must sound off for at least 60 seconds.
The sound of the alarm must be easy to distinguish to prevent misinterpreting the alarm. The NFPA suggests a continuous set of three loud beeps—beep, beep, beep—meaning smoke or fire.