Strip (trench) Ventilation – Part 2

TACTICS
Safe and efficient roof ventilation operations are dependent on Standard Operational Procedures (SOP’s) designed to provide a basic knowledge that can result in effective and safe operations, regardless of the conditions that are encountered. SOP’s are the result of training, experience, and pre-fire planning. Prior to strip ventilation operations, the following considerations should be evaluated:

LADDER AND APPROACH THE INVOLVED AREA FROM THE UNINVOLVED AREA
A minimum of two ladders should be raised away or opposite the location of a fire. This allows personnel to start and return to the strongest portion of the building and their means of egress.

LADDER THE STRONG AREAS OF THE BUILDING-ROOF
Normally, the corners of a building offer personnel the ability to ladder the strongest portion of a building, and not place ladders over horizontal openings (i.e., windows, doors, etc). Other areas that offer strength are hips, valleys, ridges, etc.

RAISE THE FLY OF AN EXTENSION LADDER-AERIAL DEVICE ABOVE A PARAPET OR ROOF TO BE EASILY SEEN
If a ladder is a primary means of egress from a roof, make it easy to locate. Therefore, do not limit the extension of a ladder above a roof-parapet to 3 or 4 feet.

PERSONNEL-EQUIPMENT
Roof ventilation operations are simplified and safety is increased (accountability) when a minimum of two firefighters are utilized. The following equipment should be considered as the basic minimum necessary to accomplish roof ventilation operations:

SCBA
Communication capability
Pick-head axe (used for prying, and as a back-up for power saws)
Pike pole, trash hook, or other suitable tools for removing cut sections of roof decking
Power saw. Historically, the rotary saw has been widely utilized as a viable roof ventilation tool, although size, weight, and the “gyroscopic” effect of the blade often detract from its effectiveness. In applications other than metal-deck roofs, the modern chain saw has proven to be a superior roof ventilation tool due to its effectiveness and ease of use-which often translates into firefighter safety.

General features that adapt a chain saw into an effective roof ventilation tool are as follows:

– Minimum engine size of 4 cubic inches (adequate power for multiple layers of roofing material
– Sprocket tip guide bar between 16 and 20 inches in length (cooler running chain and reach)
– Large air cleaner (increased time in smokey conditions)
– Muffler guard (normally a piece of aluminum on front of the muffler which minimizes maintenance and clean-up operations)
– Carbide-tipped chain (superior to standard chains)

READ THE ROOF

Before leaving a ladder and walking across a roof, personnel must take the time to observe the roof and any visual conditions. A few considerations are:

– What is the location of fire and is fire showing through the roof?
– Is a portion of the roof sagging, are there heat blisters?
– Does the roof have ventilators, vent pipes, skylights, and are they issuing smoke?
– Communicate with interior fire attack crews on interior-attic conditions, and/or the location of fire.

DETERMINE THE TYPE OF ROOF
This can be easily accomplished by pre-fire planning (a prior knowledge of a building-roof) or quickly removing a small piece of composition (or other material) from the roof covering only. This is easily accomplished with an axe or power saw and will reveal the type of roof decking below the roof covering. As an example:

Corrugated metal indicates a metal-deck built-up roof with open web bar joists
1X6-inch sheathing indicates a conventionally constructed roof
Plywood, particle board, OSB, etc. on a newer building is an excellent indicator of lightweight construction

DETERMINE THE LOCATION AND EXTENSION OF FIRE
Prior to any roof ventilation, the location and/or extension of fire must be determined. In conjunction with knowledge of the type of roof, the feasibility of a strip ventilation operation can be quickly determined before leaving the route of egress (ladder). The location-extension of fire can be determined by:

Visual size-up. What areas of the roof are issuing fire or smoke?
Small inspection-indicator openings (kerf cut, etc) can be cut with an axe or power saw in the roof decking and utilized to determine the location-extension of fire. Consider the following four conditions showing from an inspection opening:

– Fire
– Black, hot, pressurized smoke
– White, lazy smoke
– Nothing

Additionally, always remember to consider pressure, color, and temperature of smoke.

DETERMINE VENTILATION FEASIBILITY
If you have a basic idea of the type of roof you are standing on (fireground time) and know where you are in relation to the fire (area of strength or weakness), there should be no reason for you to be standing over a fire area (particularly lightweight construction) attempting to cut a ventilation opening in a roof!

SOUND THE PATH OF TRAVEL
Sounding with an axe, pike pole, trash hook, or other suitable tool in front of the intended path of travel will verify a roof’s safety. Remember, if you sound with your feet, they are connected to your body.

WORK FROM THE STRONG AREA AND/OR TOWARD THE LADDER-MEANS OF EGRESS
Ventilation cuts should be designed to start in the weakest portion of a roof (toward the fire) and finish in the strongest portion of a roof (away from the fire).

KEEP THE WIND AT YOUR BACK
When possible, ventilation cuts should be planned to keep the wind at the back of personnel.

IMPLEMENT THE CONCEPT OF “TIMING” TO STRIP VENTILATION OPERATIONS
As strip ventilation operations can be a time and resource intensive operation and an opening can accelerate the travel of fire to its location, conduct strip operations as two distinct operations. The first operation is to cut the strip. The second operation is to open the strip opening.