Smoke Detectors Req'd Below Theater Balcony?

12/2/2020

We have an auditorium project with a walkway that is constructed beside the seating area at the first and second levels. The second level has been provided with beam-type smoke detectors.

There is a suspended ceiling below the walkway which is approximately 6-feet (2 m) from the wall. Do we need smoke detectors below this suspended ceiling?

The design currently has smoke detectors only inside ceiling void spaces below the walkway - is this in compliance with NFPA 72?

The fire alarm contractor is arguing that if a fire originates at the floor level below this walkway, it will be easily detected by the beam detector at the second level due to the smoke buoyancy.

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3 Comments

Franck

12/2/2020 11:01:39 am

If there is a possibility that the smoke get trapped for a long time below the balcony (for example, if you have edges at the bottom of the balcony), it could be advisable to provide smoke detection system below them.

In all cases, if you have doubts, you can still make a fire detection ecceptance test.
In Europe, it is a common practice to test the efficiency of smoke detection systems with an approved testing system representative of actual conditions, such as British Standard 6266 for electrical hazards (standard PVC cable burn-out test or Rosco type non-toxic smoke machine).

An example of the “heated wire test” procedure is also provided on Annex B-2 of NFPA standard 76 (Standard for the Fire Protection of Telecommunications facilities).

There are some specified testing procedures, corresponding to the type of smoke expected in the area.
The princi^ple is to generate smoke at the ground level and check whether the installed detection system react rapidly.

We highly recommend them whenever there is a serious doubt on the efficiency and reliability of the system, such as:
• When there is a high level of ventilation in the area (which could prevent the smoke to reach the detector’s position), such as for electrical or computer rooms. In that case, the acceptance test is to be performed under normal operating conditions (i.e. with the ventilation in service).
• When there are doubts on the position or number of smoke detection devices.
• When the distance between the floor and the ceiling is important. The higher the ceiling, the more chance to have air movement preventing the smoke to reach the detection device. In general, it start to be problematic with height over 9 m (30 ft).

This is a performance test, not a simple functional test of the smoke detection device (by using aerosols directly applied at the device),

NATARAJAN A.S.

12/4/2020 11:05:40 am

Thanks for the detailed response

Franck

12/2/2020 11:03:35 am

If anybody reading this post has additional information about recognized samples used for this type of acceptance smoke test in the US (in addition to the reference in NFPA 76), it would be very helpful.

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