When using solid streams to protect exposures, what should be avoided?

When protecting exposures using solid streams, it is essential to avoid directing elevated streams into natural ventilation openings for several reasons. Fire behaves differently in structures with ventilation systems, and directing water into these openings can unintentionally push the fire’s energy back into the building. This can increase the intensity of the fire and create dangerous conditions for both firefighters and civilians. It can also lead to undue smoke and fire spread, hindering containment efforts.

In contrast, other practices mentioned—such as spraying water at high velocities or aiming at structures rather than the fire—could result in issues like water spray losing effectiveness or spreading the fire more widely, but they do not inherently pose the same risk of exacerbating the fire's behavior. Similarly, using foam instead of water may be a tactical consideration but is not inherently dangerous regarding exposure protection with solid streams. Therefore, the most critical point here is the risk associated with directing water into ventilation openings, making it necessary to choose and direct streams carefully to keep fire dynamics in check.