By Mark van der Feyst
No matter what brand of positive pressure fan your fire department has, it will have the same principle of operation. There will be a motor, either electric or gasoline powered, attached to a frame body, which turns the fan blades. The fan blades will be protected by a metal shroud, which prevents body parts or foreign objects from coming into contact with the blades.
The blades of the fan are made from a plastic material strong enough to withstand the high speed revolutions and air current production. The danger with the blades is that they can break under stress when the fan is running. Normally the fan will be set up in front of the opening, started and then measured to see if the cone of air is being produced around the opening. When it has to be adjusted, the fan will be moved either forwards or backwards to obtain the proper cone.
Moving the fan creates stresses on the shaft of the blades. The sudden jerking of the fan body can cause the shaft to break and throw the fan blades out of control. Even though there is a protective shroud around the blades, it will not guarantee containment. If you have to move the fan, shut it off, then move it.