FAN FAQ TOPICS:

Best seller Fan ID - serial numbers Carbon Monoxide / CO Levels Electric fans and GFCI Exhaust extensions Honda GC versus GX motors Negative pressure ventilation (versus PPV) Fan lifespan and durability Fan stability and walking Safety Light option Noise levels

Propeller composition and blades Wood versus metal propellers Wheels - Pneumatic, Solid Fan placement Horsepower and size Confined space ventilation Shrouds Troubleshooting Thrust Warning

How should the fan (or fans) be positioned/placed for optimum PPV?

- Also on this page: Positioning of Multiple Fans
- Also on this page: Positive Pressure Protection

See also: Third party test results showing how well VENTRY Fans do compared to the leading box fans at different distances from the door.

WHERE TO PUT A VENTRY FAN: A good rule of thumb is to set the fan back 1.5 times the height of the opening you are ventilating through (illustration). For balloonists, this is farther back than most are used to. For firefighters on residential fires, it is generally 10 to 15 feet from the entry point, allowing fire fighters to access the door without delay and without tripping over the fan. With VENTRY Fans, it is better to be too far away than too close because volume drops off much slower if you are too far than it does if you are too close. When a PPV Fan blows air in and smoke pours back out the top of the door, the fan is too close to the entry point. It is the tight air cone of VENTRY Fans that allows them to be placed far back from the target.

Click illustration above for larger view of PPV Fan placement

The tripod frames also help allow VENTRY fans to be set further back, because they elevate the air stream over the stairs instead of needing to be tipped. (Legs also prevent the pickup/ejection of debris, allow greater air supply to the prop, and stand on uneven ground and over obstacles like hose…) Ground-hugging fans must be propped up with additional items, or must be aimed upwards which often activates the engine oil alert features and shuts them down, just when they are most needed. By aiming horizontally/directly into the structure from a ways back, VENTRY Fans also provide minimal disturbance to the thermal balance – they don’t bounce the air off the ceiling but instead push fresh air directly into the lower portion of the structure.

Further, the quality of the air stream on a PPV Fan is very important. If you hold a handkerchief in front of any multiple-blade fan and move it around within the air stream, you will find that the strength of flow varies greatly within the circular plane. The strongest points are often at the outer edges of the circle and hit the outside of the door when properly sealed, thereby leaving the weakest points in the center to enter the structure. With VENTRY Fans, the air cone is very focused and uniform across the entire stream. You won’t lose the strongest part of the air stream on the edges of the door – instead, the air is directed into the structure.

The elevated position of a VENTRY Fan allows the geometry of aiming squarely at the entrance so a door seal is much easier to establish. Also, air stream momentum is preserved so fresh air drives deep into the structure instead of bouncing off the ceiling.

We did a lot of engineering and design work on the prop to create a uniform tight air stream. Put our fan in the rose garden and let your firefighters use the sidewalk for advancing their hose line.

How should multiple fans be placed for ventilation?
(Mall ventilation test in Seattle)

When multiple fans are required, placement side-by-side generally yields more volume while placement one-behind-the-other yields more pressure. This is a simplistic rule, so please call us regarding your specific placement questions. If you have a large fan and a small fan, again, side-by-side is probably best. If this is not possible, we recommend placing the larger fan in front (closer to the entry point) and putting the smaller fan behind it to seal the doorway.

Multiple propane-powered VENTRY Fans are shown above being used to ventilate millions of cubic feet of air at a shopping mall. Click the image to enlarge.

In the photo shown above (which was pulled from a video so the quality is lacking), multiple VENTRY PPV Fans are positioned side by side to ventilate a huge shopping mall in the Seattle area. We conducted this experiment in Seattle, using six VENTRY fans to remove the smoke from this huge commercial structure.

In the picture above, far in the background where you can see a dot of light, two more VENTRY Fans are at another entryway. The final configuration utilized three fans each at two different entryways, with the smoke exiting a third. In this way, the mall was successfully and thoroughly cleared of smoke in 8 minutes. This dynamic combination pressurized a portion of the mall where smoke had not yet gone and ventilated the other. During ventilation, we stood at intersecting hallways in the mall and watched the smoke literally turn the corner and go toward the exit! This combination did a terrific job of clearing all smoke in a short time and absolutely no smoke remained in the rafters or side shops.

A new mobile ventilation unit was also demonstrated that day. In contrast to the huge truck-mounted fan, the six VENTRY Fans used...

• cost around $12,000 instead of $250,000
• were positioned and in-action in less time
• were able to pressurize and ventilate from multiple points simultaneously, prevent ing smoke from being blown into unaffected areas
• allowed for precise control of the smoke and moved it along a planned, predictable path
• required far less space, maintenance, and training
• pushed 29,500 cfm each for much greater overall air volume

After witnessing the performance of these moderately sized VENTRY Fans in relation to the mobile ventilation unit, the mall developer was able to avoid purchasing a built-in smoke removal system or a large, expensive, truck-mounted blower. Instead, six VENTRY Fans were purchased and are currently kept on-site for smoke removal and positive pressure ventilation.

Positive Pressure Protection

Multiple fans are also useful in a method known as Positive pressure protection or PPP, also known to some fire fighters as a positive pressure sandwich. Fans can be used to greatly delay the spread of fire through pressurization of adjacent areas in multiple-room structures. For instance, if a fire is burning in one shop of a strip mall, pressurizing adjacent stores with multiple fans can prevent the fire from spreading into them. As in the case of the mall above, fans were used at two locations, one of which pressurized unaffected areas of the mall and controlled the flow of smoke, channeling it toward the exit instead of into all the shops in the mall.

Please give us a call if you would like more details on the amazing mall experiment or further instruction on PPP.

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