The legs on VENTRY Fans allow for MAXIMUM AIR VOLUME. The higher the air volume the better for effective ventilation! VENTRY Safety Propellers pull in air from many directions -- above, behind, and even below. When raised, the fan is no longer trying to pull air out of the dirt! As more air is able to reach and supply the propeller, CFM increases (see graph below).
Extending the legs on a VENTRY Fan will also increase scene safety and make your high performance Safety Propeller last a very, very long time by preventing debris pick-up.
At a minimum, extend the legs 6 inches every time you run your VENTRY Fan.
With VENTRY Fans, it is better to err on the side of being too far away rather than too close! In general, air volume is best when the fan is about 8 feet from the door. It then drops off slowly as the fan is set farther away, but drops off very quickly as the fan is placed closer and closer to the door (as shown in graph at right).
Placing the fan far away from the target also keeps the access clear and the fan well out of the way. A ppv fan should never be an obstacle to firefighting crew and victims!
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, narrow air cone produced by the VENTRY Safety Propellers that allows VENTRY Fans to be placed far back from the target and entrain air through the entrance (as shown in the illustration at the top of this page). For more on this topic, see the page on fan placement.
Our recommendations come from more than 20 years of direct firefighting experience, customer feedback, and third party testing. They will vary with conditions and they are specific to VENTRY Fans.
All customers should experiment with their fans to determine best practices for their own department and the conditions in which they operate. Click here for a simple experiment anyone can do to test a ventilation fan.
Please feel free to call us with questions. We have experts on staff to help and who are happy to discuss and share ideas.