Posi-Ventilation System
(Patent No 7,565,773 B1)

At rear of building, fan #1 on top of vertical duct runs continuously. Fan malfunction alarm turns on fan #2. Air stopped entering front wall lower intake vent and short circuited designed air flow by entering opened back door. Air exits through low level back wall exhaust vent, leaving space unventilated. With Posi-Vent System, air exits building off patented sloped sump trench with doors opened or closed. Elevated Floor grating yet to be installed over patented slope floors and trench. Posi-vent tube goes in next over trench with elevated flooring filling in. Posi-Vent tube runs across the middle of the elevated floor grating of the spill containment sump. Attach a duct to flange on sump wall and exhaust heavier than air fumes.

Haz-safe Buildings’ Posi-Ventilation System in Regard to Codes

a. All Factory Mutual 6049 Standard Approved buildings with Damage Limiting Construction are required to have explosion relief.  Factory Mutual’s instructions to all hazmat building manufacture states, “This building incorporates damage limiting construction (explosion relief) panels. These panels are not fire rated. This may compromise the fire rating on any wall that incorporates such panels…” 

b. UL Listed and FM Approved fire rated dropdown shutters can be installed over the inside of the non-rated explosion relief panel openings which solves the problem of explosion relief panel openings  not being fire rated.

c. Blast shafts also can dramatically reduce the effects of radiant heat and blast emanating from explosion relief openings when applied over the outside of the openings (requires approval by local authority having jurisdiction).

d. BOCA Code Paragraph # 418.3.1.4 says, “…explosion relief shall be provided as specified in Section 417.5.1, or shall be equipped with the equivalent mechanical ventilation …” NFPA 69 Explosion Prevention Systems paragraph 3-1  states, “The technique of combustible concentration reduction can be considered…where the concentration of the combustible can be maintained below the lower flammable limit.” In other words a fume removing systems prevents explosions.

e. NFPA 30 Flammable and Combustible Liquids Code paragraph # 6.4.2.7.1 requires mechanical ventilation have six air changes per hour with vents at 12” off the elevated floor which shall miss the fumes from a few inches above the elevated floor to the bottom of the sump…

Haz-safe combination of sump slope floors down to a slope trench (liquid chemical spills and fumes are gravity pulled down the slopes and to the lower end of the trench), posi-ventilation duct over the trench pulls the fumes off the trench out and up to the fan on the roof. No fumes in the building results in no chance for an explosion. System is failsafe with a back up fan and both fans on automatic standby electric power. The biggest benefit is all the room’s walls without explosion relief remain fire rated. (System requires approval by local authority having jurisdiction). This system is cost effective when compared to explosion relief panels, fire rated dropdown shutters and blast shafts.
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Outside air is drawn into top of box in left photo by internal fan #1 and pushed through Hepa filter and end wall. Photo on right shows duct on inside of same wall. Left photo has floor grating removed exposing tops of two (one for each sump) Posi-Ventilation tubes. Fumes enter holes underneath tubes and then are ducted up and out through wall openings. Outside same wall, fumes are ducted to central duct and exhaust fan. This ventilation system removes all heavier-than-air fumes, eliminating need for explosion relief panels.
Posi-Vent tube just back from the hot dip galvanizer. Typical are 2" diameter evenly spaced holes on bottom of tube and staggered from one side to the other. Prototype hand operated gate was tested and failed (new design works) in adjusting the opening to provide a means for each hole to pass same volume of air. Posi-Vent tube is an integral part of the support steel for the elevated flooring. Tube is a minimum of 2" above the upper edge of the patented sloped trench welded to lower edge of sloped floor (See Arrows).

Posi-Ventilation Cross Sectional Views

Single Ventilation Fans
Posi-ventilation system is best. Most 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 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).