There are multiple reasons why accessing the roof in a fire or emergency situation may be critical. More often that not, our main objective is vertical ventilation. A well-executed roof vent will control the fire and smoke and allow firefighters to work in a safer environment below.
This will also potentially lead to more rapid occupant removal and fire extinguishment.
In training firefighters, I frequently remind them to practice continual size-up and safety on the fire ground. Safety should not cripple or slow operations. In fact, acting safely in a well-planned, coordinated attack is often more rapid and at times appears more aggressive.
Roof operations are dangerous by nature. You are often working over the fire load on an elevated surface that is in some cases pitched. That is why firefighters on the roof must operate with full protective clothing and SCBA.
When possible, use an aerial ladder or aerial platform. On a pitched roof, an aerial ladder will often be insufficient; in these cases use a roof ladder. Whenever a crew is operating on the roof, be sure there is a second form of egress.
As is with our typical size-up considerations, incident command will need to assess the roof structure before operating in and around them. Be on the alert for truss-type roofs. These roofs are particularly known for early collapse without warning.
Take note of flat roofs that appear to be heavily loaded. Some will have mechanical systems, water towers, or other structures that, when under a fire load, may increase the likelihood of collapse.
Be aware that if a building has had a substantial renovation, it may now have an inadequate roof structure.
Understanding basic roof structure and framing will not only help you make proper vents, it will help you know the time you have available to operate. It will also give you a good understanding of how to approach the various type roofs and where to make the appropriate cuts without causing or promoting collapse.
Various National Institute for Occupational Safety and Health and National Fire Protection Association reports claim that it is unsafe and unnecessary for firefighters to conducted operations on a roof that has self-vented.
Specifically, the May 4, 2003 NIOSH report says, "It is not safe to assume that the roof is satisfactory as a working platform until definite signs of collapse are evident. The basic assumption should be that the roof is questionable, until valid information to the contrary is determined, either from the pre-fire plan or fire ground observation. . . . While time-to-failure cannot be accurately predicted, the time the structure has been burning must figure in the fire ground commander's thinking. . . . Once the structure itself is involved in the fire, it is deteriorating in an unknown manner and rate."
In that particular fire there were issues sited with the placement of the vent holes. The best possible vent hole is directly over the fire.
This also means the firefighters making the roof vent are in the area most likely to collapse because the framing members are being compromised by a fire load.
While on the roof, use wind direction to help place your crew on the proper side of the vent hole to limit additional exposure to heat and smoke.
Consider the weight of your crew. Firefighters operating on the roof will add to the live load of the roof. Also, the hole size, depth, and location can also lead to premature collapse.
When considering roof operations, roof pitch and weather can also lead to issues. Clay tiles, slate, and metal roofs can be particularly slippery with minimal rain or snow. As the pitch of the roof increases the risk of falls and accidents also increases.
Calculate the risk vs reward component before placing firefighters on the roof. Remember, when operating on the fire ground with roof operations as a component, continual size-up and assessment of the operations is critical. Fire departments should also have standard operating guidelines in place for vertical ventilation procedures.