Over the last 20 years we have seen the use of Positive Pressure Ventilation (PPV) in offensive structural firefighting evolve. This concept got it’s start in the United States back in the early 1980’s on the west coast. It was originally utilized to assist the attack crew with a high flow of air behind the attack crew to assist them in making the push to the seat of the fire.
It was used with a fair amount of success when it was conducted in coordination and proper timing with ventilation opposite the attack crew entry. Over the years as this tactic has evolved across the country, it has morphed into what I believe is a dangerous tactic of uncoordinated use of high flow fresh air into structures without the proper vent opposite the attack crew before they make their entry.
This practice has resulted in rapid fire growth and “blow back” of that growth on many attack crews. There are several videos available online to demonstrate this predictable fire behavior. Here is one example. It is in German but it speaks volumes.
How do we use PPV properly?
First , I am not an avid fan of the use of this tactic in the initial stages of attack. This is primarily due to the fact that after functioning in the fire service for many years, I have come to the conclusion that we (the fire service) are not very good at being coordinated in our attack 100% of the time. In utilizing PPV we must be 100% coordinated between the attack crew and vent crew 100% of the time. The end result of an uncoordinated use of PPV could be fatal and has been proven to be dangerous.
So, how does PPV work as a tactic in the initial stage of attack? We must first have a very good idea where the fire is located. We must have a charged, bled and adequate sized and staffed attack line at the entry point ready to go. Then we must create or ensure that an adequate outlet (vent point) at least 2/3 the size of our inlet (vent point) is open opposite our attack position. Then and only then can we put our fan in service behind the attack crew’s entry point so that the airflow covers the doorway completely (to check this principle, no smoke should be exiting the doorway). Be prepared for rapid fire growth, as it will occur.
If smoke is exiting at the doorway (inlet) then two things are possible. The fan air curtain is not covering the entire opening or worse the outlet vent point is inadequate to handle the heat and byproducts due to fire growth. If the latter is the case, do not put your attack crew on a path to destruction. Shut the fan off and make more or larger openings opposite their advance.
PPV is a great tool, you just have to know, and meet, all the criteria for use! Some other excellent uses of PPV are for smoke removal, maintaining clear and positively charged stairwells in occupancies, and as a means to move/push gases (HazMat) in a direction away from occupants.
In conclusion, if you cannot meet the parameters for using PPV in attack mode then don’t. Use the tried and true method of manual means of Tactical Ventilation. If you train, use and critique PPV on fires you will find it to have many benefits, just remember the drawbacks are painful! Until next time, be safe stay low and keep learning your life depends on it!!