Where should the electric fan for negative pressure ventilation be placed?

The electric fan for negative pressure ventilation should be placed at a high point in a door or window on the leeward side. This positioning is crucial because it allows the fan to effectively exhaust smoke, heat, and other harmful gases from the structure. By placing the fan high, it capitalizes on the principle that hot air rises, enabling the removal of the warmer, more buoyant smoke that tends to accumulate near the ceiling.

Additionally, positioning the fan on the leeward side ensures that it draws fresh air in from the windward side, enhancing the flow of air and creating a more efficient ventilation process. This setup not only helps in clearing smoke and improving visibility but also aids in maintaining a safe environment for firefighters and any occupants who may still be inside.

The other options do not optimize the effectiveness of the ventilation process in the same way. Ground-level placement, for example, would not efficiently address the smoke and heat that accumulates higher in a space. Central placement might not provide the desired airflow dynamics, and placing the fan in the attic can be problematic as it may not effectively ventilate the lower levels where the smoke is typically concentrated.