What characteristic makes a box fan vital during smoke removal?

A box fan's ability to circulate air effectively is essential during smoke removal because it helps to displace and push smoke out of an area. Good air circulation facilitates the movement of contaminated air (containing smoke and other harmful particulates) out of the space while bringing in fresh air from outside. This movement is critical in quickly and efficiently clearing out smoke, improving air quality, and making environments safer for anyone remaining in or entering the area.

While other characteristics like being lightweight or adding pressure are beneficial in certain situations, they do not address the primary function needed during smoke removal. A fan that effectively circulates air directly contributes to the overall process of ventilation and smoke mitigation, thus making it a vital tool in such scenarios.