Requirements for Fire Smoke Dampers

[mshields]

Does anybody know where the requirements for smoke and fire smoke dampers are?

i.e. the rule that says you have to have a fire alarm Control Module that holds it open, Fire Alarm Monitor Modules to tell the FACP the position of the louver, etc.

Most of my work is in MA but I'm guessing this is found in NFPA 1 (like many states, our Fire Code is based on that standard albeit with MA ammendments).

Thanks,

Mike

 

[luckylerado]

I think you want NFPA 92. I don't believe either of those two rules are in there though unless it is a recent code cycle revision. Maybe a local/state thing.

 

[gadfly56]

I think you want NFPA 92. I don't believe either of those two rules are in there though unless it is a recent code cycle revision. Maybe a local/state thing.

Yes, NFPA 72 doesn't have anything substantive on fire and fire/smoke dampers. It just acknowledges their existence and points you to NFPA 92 and NFPA 105.

 

[MNWildcat]

Building codes and Mech codes usually have text on how to control them and how they are to function (smoke detector vs duct detector vs total area coverage.
Also note that smoke dampers have to close when the HVAC unit is turned off. Most smoke/duct detectors are only rated down to 100f/m air velocity.

 

[gadfly56]

Building codes and Mech codes usually have text on how to control them and how they are to function (smoke detector vs duct detector vs total area coverage.
Also note that smoke dampers have to close when the HVAC unit is turned off. Most smoke/duct detectors are only rated down to 100f/m air velocity.

The requirement for duct detection kicks in at 2,000 ft³/min. To be down at the lower limit, you'd need a duct with a cross section of 20 ft². That's a square larger than 4ft X 4ft, or slightly less than 5ft X 5ft. You couldn't make a connection of that duct size to a 2,000 cfm unit. Even residential ducts run over 100 ft/min.

Air Duct Velocities

Typical air duct velocities in applications like ventilation systems or compressed air systems.

www.engineeringtoolbox.com

 

[topgone]

The requirement for duct detection kicks in at 2,000 ft³/min. To be down at the lower limit, you'd need a duct with a cross section of 20 ft². That's a square larger than 4ft X 4ft, or slightly less than 5ft X 5ft. You couldn't make a connection of that duct size to a 2,000 cfm unit. Even residential ducts run over 100 ft/min.

Air Duct Velocities

Typical air duct velocities in applications like ventilation systems or compressed air systems.

www.engineeringtoolbox.com

Isn't there a typo?
Ex. Q = 2,000 CFM.
Recommended air velocity thru the duct = 1,000 FPM.
Then, the area of the duct will be = 2 sq. feet? ( A = Q/V)

 

[MNWildcat]

Unit shutdown is a different issue from damper control. My comment was related to air velocity (ft/min), not air volume rate (cfm) for damper control.

For smoke damper control, EVERY smoke damper or fire/smoke damper requires one of the methods I noted above to shut the smoke damper down upon detection of smoke, regardless of the duct size or cfm. My point was that when the unit is shut down, the air velocity drops to zero, and no smoke will go through a duct detector or even a regular smoke detector. Therefore the hvac system has to send a signal out to close all the smoke dampers so in the event of smoke spread it will not sneak through a smoke damper.

For unit shutdown:
The size of the duct is based on air velocity. But in most systems a 2000cfm unit is not all that big. Actually, the code states 2000cfm SYSTEM, so if you have two or more 1500cfm units feeding the same space (e.g. multiple RTUs for a big box store), it needs unit shutdown from the FA for all the RTUs. When the unit shuts down, it doesn't matter if air can go thru the duct detector since the unit is shutdown, and it's not a rated smoke wall/barrier.

 

[topgone]

Unit shutdown is a different issue from damper control. My comment was related to air velocity (ft/min), not air volume rate (cfm) for damper control.

For smoke damper control, EVERY smoke damper or fire/smoke damper requires one of the methods I noted above to shut the smoke damper down upon detection of smoke, regardless of the duct size or cfm. My point was that when the unit is shut down, the air velocity drops to zero, and no smoke will go through a duct detector or even a regular smoke detector. Therefore the hvac system has to send a signal out to close all the smoke dampers so in the event of smoke spread it will not sneak through a smoke damper.

For unit shutdown:
The size of the duct is based on air velocity. But in most systems a 2000cfm unit is not all that big. Actually, the code states 2000cfm SYSTEM, so if you have two or more 1500cfm units feeding the same space (e.g. multiple RTUs for a big box store), it needs unit shutdown from the FA for all the RTUs. When the unit shuts down, it doesn't matter if air can go thru the duct detector since the unit is shutdown, and it's not a rated smoke wall/barrier.

The unit shutdown is required by code if the system allows air to stoke the incipient fire or transport smoke to other points rooms, as in the case of VRF HVAC, precision air conditioners--> the >2000 CFM regulation. On centralized units (AHU) smoke detectors are there to activate the closing of dampers in the event of fires. The rationale is that HVAC systems dampers even when not receiving outside air can allow smoke to enter rooms passively if dampers are open. Most people die of smoke inhalation than getting burned, you know?