Positive pressure fans are effective against winds of what maximum speed?

Positive pressure fans are designed to create an artificial pressure differential within a structure to aid in smoke control and to improve visibility and air quality during fire operations. They work effectively by pushing clean air into a structure, thereby pushing smoke out through openings.

The effectiveness of positive pressure fans diminishes with increasing wind speeds, as strong winds can disrupt the airflow created by the fans and introduce unwanted air currents. Maximum wind speeds of up to 25 mph have been identified as an acceptable limit for successful operation of these fans. Beyond this speed, wind can significantly impact the ability of the fans to manage smoke and maintain the intended pressure relationships within the space.

This understanding is critical for fire service personnel when assessing the viability of using positive pressure ventilation under various weather conditions during incident management.