How can recirculation be eliminated during smoke ejection?

When it comes to smoke ejection, the goal is to effectively remove smoke from an area to improve visibility and safety for both firefighters and potential victims. Recirculation occurs when smoke that has been pushed out begins to flow back into the space due to pressure changes or improper fan placement.

completely blocking the opening around the fan prevents the re-entry of smoke into the structure. This creates a solid seal and maximizes the efficiency of the fan by ensuring that the air being pushed out is not allowed to flow back in. In scenarios where gaps exist around the fan, the negative pressure created by the fan can draw smoke back into the area, defeating the purpose of ejection.

Other methods like adjusting the fan position or keystoning, while they may help in certain contexts, do not provide the same level of assurance when it comes to maintaining the integrity of airflow and preventing recirculation as completely blocking the opening does.