Question

what is needed to reduce smoke hazards?
a large fan
big air filters
adequate ventilation
holding your breath

Explanation:

A large fan may not effectively remove smoke in all situations. Big air filters can help but are not the most fundamental solution. Holding your breath is a temporary and not practical long - term measure. Adequate ventilation is the key as it allows the smoke to be carried out of the area, reducing its concentration and hazards.

Answer:

adequate ventilation