Yes, the Architect is correct. The Engineer designing the HVAC & Alarm / Detection system may not be aware that there are a class of detectors called 'multi-criteria detectors'. They typically have more that one detection technology within them and are set-up so they have to get a signal from both parts of the detector before it issues an alarm signal to the fire alarm system.
You may also want to request that some QUIET exhaust fans be installed over the stage that can be manually switched on when you are using heavy atmospheric effects. The drawback to this is that depending upon the effect you are looking-for it may shift the air flow and redirect your effect.
Whenever you are planning on using atmospheric effects you should do several run-throughs with the intend equipment with a representative from the fire department present so they can disable the alarm system if it shows signs of tripping.
You have to know your effect: hazers, 'juice' foggers, nitrogen foggers, CO2 (dri-ice) foggers, and the many variations all create effects that can rise or fall depending upon the air flow patterns you have and/or the elevation of the fog source relative to the return air intakes. Tech Rehearsals must be representative of the actual effect you want to use in the show. Don't 'hold-back' to get the test done then later decide you want to have twice as much fog. Also, don't change your fog juice or the fog machine after you have done the test. No two technologies can be considered equivalent. If you change the method by which you are producing or distributing your atmospheric effects, then you need to re-test the system.
It is important that atmospheric effects are not drawn out into the seating area or into the orchestra pit, if any. The general airflow design should be to draw the air towards the upstage wall. This means placing Return Air grilles (R/A) in the orchestra pit or along the front face of the stage apron are generally NOT a good idea.
The alarm system and the smoke / fire detectors must all be very closely coordinated to work in harmony with Smoke Vents, In-Duct sensors, Duct Shutters, Automatic Fire Door releases, and the Fire Curtain release. Out of sequence operations can reduce the effectiveness of the overall fire and smoke containment function, and in some circumstances cause the Fire Curtain to bind while closing and prevent it from closing fully in the amount of time allocated.
Another issue you need to discuss with your administration and the design team is the acceptable noise levels on the Stage and in the Audience seating areas (and sound control booth if it is not directly in the seating area). The Noise Criteria (NC), or Preferred Noise Criteria (PNC) must be defined before the HVAC system is designed, and it must be checked to assure compliance with the defined level if there are any variations from the design by the contractor, and it must be checked to see if it meets the design noise level once the building is complete. The owner (your school district) MUST put provisions in the contract that will hold the Architect, Engineer, and Contractor's feet to the fire to meet the pre-agreed upon NC or PNC levels. If they miss the mark there must be a huge penalty to pay. Without consequences, they will usually NOT get this right, and once it is wrong, you can't (reasonably afford to) fix it. You get exactly one chance to get it right. If they get it wrong, it will be noisy forever.
Why is this important? The NC or PNC level determines the noise floor for the performance space. If the HVAC is too noisy, then microphones will pick-up the sound and it will be present on all recordings. Most good recording microphones have a self-noise (e.i.n. - Equivalent Input Noise) of around 20 dB(A), so any noise in the room above that level is probably going to be audible in the recordings. It is (unfortunately) necessary to remind all the parties involved in the project that 'Auditorium' means 'Place to hear'. If you don't get this right, it nullifies the whole point of the project. Noise from the HVAC system is predictable and can be scientifically estimated before any construction is done, so there is no excuse for not designing the system to be quiet. Aside from the recording aspect, noise masks the subtle nuances of musical instruments and small voices, The parents and grandparents that come to the shows want to hear their child's voice. To build a noisy room defies that simple basic requirement. Don't just 'take their word for it' - have them produce the sound level prediction documentation so the school district knows this has been done properly. Microphones and speaker systems cannot fix this, so don't let them tell you that 'it will be OK because they are installing a sound system'.
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Erich Friend
Theatre Consultant
Teqniqal Systems
Original Message:
Sent: 11-01-2016 12:41
From: Elisabeth Ledwell
Subject: smoke alarms in duct work
Hello everyone,
We are currently renovating our theatre, and we have run into a difficulty. Our architects tell us that to meet codes, there must be smoke detectors in the HVAC duct work. We are afraid that these will detect fog and atmospheric effects. What solutions have you used to avoid having to 1)turn them off? and 2)pay for a firefighter to watch when they are off? All suggestions welcome!
Thanks!
Liz Ledwell
Falmouth Academy