In case of a fire or any other emergency, people in the premise should be warned. This warning has to be made both auditorily and visually. Because there is a possibility that handicapped people might be in the building.
HOW SHOULD WE USE AUDIO AND VISUAL FIRE ALARM DEVICES?
When a fire alarm is triggered by a smoke detector or a manual call point, fire alarm panel starts to operate fire scenarios. In almost every scenario, evacuation of people in the premise is a priority so that nobody gets hurt beacuse of the fatal effects of fire.
Evacuation procedure starts with warning of people by audio and visual fire alarm devices like sounders and beacons. Therefore the quality and project design of these devices are very imprtant.
If European Norms are taken as reference, features and performance criteria of sounders and beacons should be in compliance with EN 54-3 and EN 54-23. Audio and visual fire alarm devices should have CPR (Construction Products Regulation) certificate from a European Commission notified body.
Project Notes about audio and visual fire alarm devices
According to EN 54-14 clause A 6.5.2, audio fire alarm devices should have minimum 65 dB (A) of sound level. Or if there is a noise which lasts longer than 30 seconds, audio fire alarm device should make sound 10 dB(A) higher than ambient noise.
If there is a possibility that people might be sleeping in case of fire, audio fire alarm devices should be placed so that sound level at the bedhead is minimum 75 dB (A). Also sound level should not be higher than 120 dB (A).
As stated in EN 54-14, people who are awake should be warned with minimum 65 dB (A) sound level, and people who sleep should be warned with minimum 75 dB (A) sound level. Therefore some calculations should be done in the process of designing fire alarm system projects.
Things to consider:
• Technical specifications written in product datasheet state sound level at 1 meter distance from fire alarm sounder
• When distance from fire alarm sounder doubles, sound level decreases 6 dB(A) logarithmically
• Room doors decrease sound level 20 dB (A)
• Fire doors decrease sound level 30 dB (A)
Alternative option is using base sounders, which are placed under detectors, in fire alarm systems. So that, there will be no need for complex calculations of sound level for each point of the premise. By the way, sound level of base sounder is very important. It should not be less than 75 dB (A) at 1 meter.
What should be the visual alarm level in case of fire?
According to EN 842, visual fire alarm devices should warn people with light intensity which is 10 times stronger than ambient lighting. Also these devices should be used in places where people in the premise can see them easily.
To conclude, audio and visual fire alarm devices are essential elements of fire alarm systems. People in the premise can be warned by these devices in case of fire. Sound and light intensity levels should be considered while choosing these devices and designing fire alarm systems according to standards and regulations.
• Mavili Project Notes
• EN 54-14 Standards
• EN 842