How can recirculation be eliminated during smoke ejection?

Completely blocking the opening around the fan is the most effective way to eliminate recirculation during smoke ejection. When the opening is fully sealed around the fan, it ensures that the air being expelled is coming solely from the fire area rather than mixing with smoky air from other areas or re-entering the space. This method enhances the efficiency of smoke removal by preventing the possibility of contaminants being sucked back into the environment that needs to be cleared.

The action of blocking the opening effectively creates a barrier that directs all the flow through the fan, ensuring the optimal performance of the smoke ejection process. This is critical to maintaining a clear and safe environment for both fire responders and potential evacuees, which risk being compromised if recirculation occurs.