Dual
Ventilation Fan System
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At rear of
building, fan #1 over fan #2. |
Fans #1 and
#2 side-by-side on separate ducts, which lead down to inside separate
low level air exhaust vents. |
Continuously
run fan on right with emergency air flow switch to turn on second
fan and sound trouble alarm. Fans mounted on outside duct. |
Dual fans system
in combination with posi-vent
system over sloped trench, eliminates need for explosion relief
panels. |
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| Dual low level ventilation
draws air across the floor to exhaust vents through outside wall
and up duct chase to fans on roof. Fan #1 runs continuously until
malfunction alarm turns on fan #2. |
Lower & Upper Level Ventilation System Comparison
| GOOD |
BETTER |
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| Air
intake mixing with heavier than air vapors and exhausting at low
level same as vent opening. Gasses are directed up outside duct
chase and discharged at roof line. Even better, the fan could be
above the roof to meet N.F.P.A.91 para. 2-4.5.1 as shown in graphic
"D" on right. Dual ventilation systems have fan #1 running
continuously with sensor turning on fan #2 and sounding malfunction
alarm. |
Same
as graphic "C" plus the incoming air is forced down past
elevated floor by an inside duct or hood where it mixes with heavier
than air vapors and is drawn out of the sump through a duct up to
the exhaust opening in the wall. Hood (#1) shields opening from
small objects turned into projectiles during explosions and (#2)
keeps stored liquids from freezing in incoming cold air. Hot air
at ceiling is removed by a thermostat opening motorized dampers
at vent openings located near ceiling. System works best when energizing
fan #2 for the upper level ventilation system. |
BEST |
| The
previous Graphics "C" through "D" show ventilation
systems attempting to remove heavier-than-air vapors or fumes from
the total volume of air in the building. Explosive fumes can begin
anywhere in the building as they come off a leaked or spilled chemical
liquid. Gravity will eventually pull all heavier-than-air fumes
down into the sump floor area. When the sump floor is sloped (U.S.
Patent #6,305,131) downward toward a sloped trench (same patent),
the liquid can be collected into a smaller exposed surface area
reducing the amount of vapor coming off the liquid chemical. By
placing a posi-ventilation tube (becomes part of the elevated floor
supports) inches over the sloped trench, these fumes can be removed
from the building. Graphic "E" (y-axis) shows the posi-vent
tube (patent pending) with strategically placed holes on its bottom
surface where air and fumes are picked up and directed out of the
building wall, up a duct to a continuously running exhaust fan #1
on the roof. Graphic "F" (x-axis) shows a cross section
view of same floor of building and Click
Here to provide a close-up detail of posi-tube over the sloped
trench. If fan #1 malfunctions, a flow sensor sounds an alarm and
turns on fan #2. Both fans could be on an emergency generator or
standby circuit. A posi-ventilation dual exhaust fan system eliminates
costly non-fire rated explosion relief panels, fire rated drop down
shutters and blast shafts (U.S. Patent #6,223,473B1). |
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