Winds in excess of how much cannot be reversed with positive-pressure ventilation (PPV) fans?

Positive-pressure ventilation (PPV) is an effective firefighting technique used to clear smoke and heat from a structure, facilitating search and rescue operations and improving conditions for firefighters. However, its effectiveness is significantly influenced by external wind conditions.

For winds exceeding 25 mph, using PPV fans becomes increasingly problematic. At these wind speeds, the force of the wind can counteract the airflow created by the PPV fans, preventing proper ventilation and potentially reversing airflow within the structure. This reversal can introduce smoke and toxic gases back into the area rather than expelling them.

Understanding this limit is crucial for personnel on the scene. It underscores the importance of assessing weather conditions prior to deploying PPV tactics. By recognizing that winds above this threshold may render PPV ineffective, firefighters can make informed decisions to use alternative ventilation methods that are more suitable under high-wind conditions.

This knowledge ultimately aids in maintaining safety for both the firefighting crew and any occupants trapped within the structure.