By Mark van der Feyst
The positive-pressure fan works best when the fire conditions are not going to be a contributing factor. The fan can easily spread fire from one location to another and make conditions worse. The conditions of the fire need to be checked to ensure that flashover is not impending or achieved. If the fire is at that stage, the introduction of the fan will only speed up the development of flashover.
Having no exit opening will result in the conditions becoming worse and can push the fire around the structure. If there are firefighters inside at that time, they will be exposed to a dangerous situation and become trapped by fire. A positive-pressure fan cannot be used when there are flashover conditions, when the fire is in the basement, or when the structure is fully involved. Before using the positive pressure fan, check the conditions to make sure it is safe to use.