Flashcards in Ventilation Deck (30):
4 main objective of ventilation
Assist with access
Control horizontal spread of Fire
Reduce possibility of flashover and backdraft
2 types of ventilation holes
Heat hole (offense)
Strip Ventilation (defensive)
What is ventilation
Systematic removal of heat,smoke, and gases from structure, and replacing with cooler, clean, fresh air.
Hazards of improper ventilation
Pull fire to vent hole
Create new flow path
Must have communication with engine crew
Best ladder location for roof access
Not over window/doors
Near fire but not in danger of fire damage - in black
Near load bearing walls
Commercial 8’ in - stay on structural members
2 types of ventilation
Offensive cut- directly over fire or as close to fire as safely allows. Dangerous over light weight and Not Reccommended.
Placed well ahead of fire, should extend length of building. Must be done in conjunction with a heat hole. Heat hole first to slow horizontal spread of fire.
Sounding Roof / Traveling
Sound roof before stepping off. Stay in single file. Look for sagging. Look for signs, melted tar, sagging spots, spongy roof. Smoke production.
Center Rafter Cut
Used when cutting plywood sheathing (4 cuts)
Used to cut 1”x4” or 1” 6” sheathed roofs. Diced cuts made between rafters. Ex in middle of the rafter bay parallel to rafters with no concern of locating rafters.
Made through roof decking perpendicular to rafters. Used to locate rafters. Involves rolling rafters. Must be done on roofs covered with plywood and diagonal sheathing.
Placed over or near fire.
A single cut made through the roof decking, some width as chain saw blade. Not as effective but can be used as an alternative to smoke indicator hole.
Made from 2”x4” laid flat between rafters to provide nailing surface for edge of plywood sheathing.. Since plywood normally used is 4’ x 8’ in size a nailing block will usually be found every 4’.
A small triangular piece of roof covering (comp) which is removed from roof to expose the roof sheathing. Used to determine sheathing type and roof comp thickness.
Size and type
Typically 4’ x 8’
Plywood, chip board, and OSB
Light cut of roof covering, usually comp only. Used to facilitate the removal of multiple layers of roofing material (comp).
Light cut made with chain saw, cutting through the roof covering and plywood sheathing.. Saw is not inserted deep enough to cut through rafters. You “skim) over the top of the rafter. Used on penalized roof when performing cutting technique as louder off a purloin.
Smoke Indicator Hole
Small triangular hole cut through the roof decking made with chainsaw or axe. Used to indicate smoke and fire conditions. Should be placed along path of access or egress every few yards. Should be continually monitored . Can indicate changing conditions.
Placed on roofs to ventilate attics and building interiors. IF working correctly leave alone. 30% more effective when turbine is spinning. Let them do their job.
Plumbing pipes that extend from inside of structure through roofline. Vent pipes can BE CONSTRUCTED FROM ABS Plastic, cast iron, or steel pipe. IF appear to be growing out of roof should be indication that roof has sagged or dropped. Condition as “growing vent pipes”
45 degree Inspection Cut
If rafter type and rafter direction are unknown a 45 degree inspection cut will tell you rafter type and rafter direction, the sheathing type, thickness of roof comp and when complete, it can act as a smoke indicator hole. Accomplished by cutting through the roof decking at a 45 degree angle toward or away from any exterior wall. The 45 degree cut will ensure saw will intersect a structural member. Roll rafter and continue for 6-10 inches. Complete cut by removing triangle decking over structural member.
Two cutting methods for vertical roof ventilation operations
Center Rafter and dicing
Fold Back Method
Vent technique primarily used on flat light weight panelized construction commercial roofs. Considered a Defensive operation designed to stop horizontal spread of fire in overhead. Often referred to as a strip or trench operation.
Locate the fire
Identify and control flow path
Cool heated space
Explain Center Rafter Louver Cut
-minimum hole size
-proper sequence of cuts
-how to punch through
-48” across 48” down
-use rubbish hook or handle through hole.