Free-Flow Guards on Ventry PPV Fans

Above, firefighters discuss
training while the Ventry PPV Fan
idles quietly next to them.

All Ventry® Fans have heavily reinforced, fail-safe, free-flowing guards or cages instead of solid shrouds because they increase CFM while decreasing noise.

Free-flow guards are safe and they allow the propeller to pull air in from behind and beside the propeller—not just from behind!


  • First, in order to push a lot of air, a propeller has to have a lot of air reach it. Supplying more air to the propeller simply results in more air pushed by the propeller.
  • Second, most of the propeller’s air supply reaches it directly from the sides, straight through the open-flow guard. Efficient propellers on Ventry Fans pull air from beside, behind, and even a bit from in front of the guard before shooting it out the front of the fan (but most is from the sides).
  • Third, the outer quarter of a propeller does roughly three quarters of its work. In other words, the tips/ends of the propeller move the air, not its center. In one revolution, think how much farther the outer end of a propeller travels than the center. Therefore, the majority of the air needs to be directed to the propeller’s outer ends, not its center.

It follows that a solid shroud would block a lot of the air from reaching the outer ends of the Ventry Safety Propeller and essentially starve it of air and dramatically increase noise. This is demonstrated in this short video:

Ventry Fan guards are heavily reinforced for safety and durability. Modern models have twice the number of outer structural components and every intersection is MIG-welded.

PPV fan users are often surprised to find that the painful racket of many fans is caused by the lack of air getting to the propellers, not the motors. Ventry Fans are known for being much quieter than common fans.

TRUE STORY: Years ago, a competitor wanted to use Ventry Safety Propellers on their fans. Shortly after sending a propeller to them for testing, they called us and were mad, saying our props didn’t work at all!

James wondered, did they have it on backwards? Instead, he learned they had a solid shroud around the propeller on their fan so he asked them to try our prop again, this time without the solid shroud. Soon after, the Safety Propeller was returned to us with a note saying essentially “Thanks, but no thanks.”

James called to find out what happened. When the solid shroud was removed and more air was able to reach the Ventry Safety Propeller, their fan fell over backwards! Rather than re-engineer their whole fan to handle the thrust produced by our propellers, they decided to stick with what they had.

High air volume and low noise are among many benefits that are due to the highly efficient design of Ventry Fans. Their unique combination of Safety Propellers, patented All-Terrain Legs, and Open-Flow Guards solve the problems firefighters face during ventilation. They are simply lighter, quieter, less bulky, and more effective than comparable fans.