http://apfmag.mdmpublishing.com/posi...of-engagement/ (The source sentence is at the foot of the page; 2nd paragraph under the heading Firefighter Safety).
From what I have read, ventilation of a fire scene using fans seems to be a vital activity while performing Positive Pressure Attack. The ventilation improves visibility by clearing thick toxic smoke away from fire crews. This means that firefighters will not stumble over, or fall through, hidden obstacles such as flowerbeds which would otherwise be masked by the thick smoke.
Shortly after the sentence in question the writer states, "We can see where we are going and never go beyond an area that the fan can clear.".
Student or Learner