What method involves pushing air into a confined space to expel contaminated air?

Positive pressure ventilation is the correct method for pushing air into a confined space to expel contaminated air. This technique involves using fans or blowers to introduce fresh air into the space, which creates a higher pressure inside the confined area compared to the surrounding environment. The increased pressure forces the contaminated air out through any openings, effectively clearing the space of harmful substances.

This method is particularly important in confined space rescue operations, as it helps maintain a safe atmosphere for rescuers and victims by removing hazardous gases or vapors. Positive pressure ventilation is typically used in situations where immediate removal of hazardous air is critical, allowing for safer entry conditions.

In contrast, the other methods focus on different principles. Negative pressure ventilation would create a vacuum effect, pulling air out rather than pushing it in, which is not what is needed for expelling contaminated air. Air exchange ventilation involves replacing the air within the space but does not necessarily focus on positive pressure or forceful expulsion of contaminants. Controlled ventilation encompasses various strategies without specifically aligning with the positive pressure method, making it less direct in addressing the immediate need to expel contaminated air efficiently.