ENGINEERED SMOKE CONTROL SYSTEMS
Introduction. By the very nature of this type of
system; some of the requirements of NFPA 90A will need to be
modified or suspended. If air movement or pressures from the
duct system are necessary to confine or control the flow of
smoke, fans should not be shutdown or dampers closed.
Specific Design Guidance
Suggested for use in large zones.
b) Smoke dampers should meet UL 555S, Standard for
Safety Leakage Rated Dampers for Use in Smoke Control Systems.
These are made in ratings of zero to four. Class 1 is a good
tight damper. Use Class 1 dampers where the return or exhaust
air may meet the outside air to prevent contaminating the supply
air with smoke. Class 2 or Class 3 dampers (with more leakage)
may otherwise be used for smoke zone dampers.
c) Return ducts used for smoke purging should be steel
fabrication. Supply ducts should be insulated for protection
from fire outside the duct.
d) Fans used for smoke exhaust should be rated for 750
degrees F continuous duty. Use an extended shaft and a
commercially available propeller on the shaft to blow air onto
the motor. The air temperature in the fire room may reach 1,400
degrees F, but this may be diluted with 70 degrees F air from
other rooms to permit use of an ordinary fan. Do not put the
motor in the airstream and do not use an aluminum fan wheel. Do
not stop the smoke exhaust fan during a fire.
Specify acceptance testing of the smoke control