What action should be avoided when performing horizontal natural ventilation?

When performing horizontal natural ventilation, it is essential to open the upwind windows first, as this allows for the controlled flow of air into the structure. By ensuring that the upwind openings are addressed before the downwind openings, it helps to establish a proper airflow pattern that can effectively remove smoke, heat, and toxic gases from inside the building.

Opening downwind windows first could lead to a situation where smoke and heat are not effectively vented from the building. This practice compromises the safety of the firefighters and any occupants within, as it may inadvertently push the smoke back into the structure rather than facilitating a proper outflow.

Using exhaust fans and creating cross ventilation can be beneficial tactics when employed correctly. However, they must be utilized with consideration for the wind direction and overall fire dynamics, which makes the order of opening windows critical for safety and effectiveness.