What type of motion should be used when applying dry chemical to a fire?

When applying dry chemical to a fire, utilizing a side to side motion is effective because it ensures an even distribution of the extinguishing agent across the flames. This sweeping action helps to cover a larger area, ensuring that the chemical is applied thoroughly and forms a barrier between the fuel and the fire, which is essential for extinguishing the flames. The goal is to smother the fire and interrupt the combustion process, and a side to side motion aids in achieving this by maximizing the contact of the dry chemical with the fire's source.

The other motions, while possibly valid in different contexts, do not provide the same level of effectiveness for this specific firefighting technique. For example, a circular motion may not cover the entirety of the fire, and an up and down motion might concentrate the chemical in a limited area rather than dispersing it evenly. Similarly, a zigzag motion could lead to uneven application and increase the risk of the fire not being effectively controlled. Therefore, the side to side approach is best for optimal fire suppression with dry chemicals.