Ventilation Techniques Flashcards
What is ventilation?
Systematic removal of heat, smoke and fire gases from structure and replacing it with cooler clean fresh air
Order for the 4 objectives of ventilation
1 saves lives
2 assists Firefighter access
3 control of horizontal spread of fire
4 reduce the possibility of flashover and backdraft
How does ventilation save lives?
Removes heated smoke and fire gases increases the chances of unconscious occupants
It helps conscious occupants to breathe better by introducing fresh cool air
Makes conditions and visibility better for firefighters to quickly locate trapped or unconscious victims
How does ventilation assist Firefighter access ?
Increase visibility and removal of super heated access for safer and quicker access
Rapid extinguishment reduce damage
Proper extinguishment will also assist in fire extinguishment , rescue,salvage and overhaul operations
How does ventilation aid horizontal spread of fire ?
Proper ventilation will reduce mushrooming which in turn reduce the rate fire can spread an area
What is mushrooming ?
Fire heat smoke and fire gases travel to highest point of building l. When they’re not released at the highest point of structure they begin to bank down and spread laterally
How does ventilation reduce possibility of flashover ?
Proper ventilation helps because the heat is removed from structure before they reach ignition temperature
What is flashover ?
When all contents in room have reached their ignition temperature. The entire room will quickly be involved with flames
How does ventilation reduce possibility of backdraft ?
The release of heat smoke and fire gases
What is backdraft ?
In a confined area of the contents reach their ignition temperature but do not have enough oxygen to support combustion . Once oxygen is introduced explosively change super heated area to an instant inferno
What types of ventilation are there?
Horizontal and vertical
What are two methods of horizontal ventilation?
Can be natural or positive pressure (mechanical)
How does natural horizontal ventilation work ?
Opening doors and windows letting wind ventilate building
How does positive pressure ventilation work?
Forcing clean, fresh air into a structure with blowers. Systematically opening windows and doors to channel the pressurized air
What is vertical ventilation ?
The opening of roof or existing roof openings (skylights, hatch covers ect)
What is the key to safe and effective ventilation ?
They is the knowledge of rafter type and direction
What’s the major difference between conventional and truss construction roofs?
Conventional are made solid pieces of large lumber usually withstand fire for much greater length of time
How do you ventilate a conventional roof ?
If time and saftey permits the roof team WILL cut heat hole directly over the fire
True or false when pertain on lightweight truss roof roof team shall never conduct ventilation operations over the fire?
True
What practice can members employ for lightweight roof ventilation ?
Trading space for time
What is trading space for time ?
Members may complete their roof cutting operations prior to fire impinging on given ventilation hole
Why is rafter type and direction important to know?
We usually cut 1x4 and 1x6 sheathing parallel to rafters
On roofs sheathed with plywood the head cut is perpendicular to rafters
What are two types of ventilation holes?
Heat hole offensive
Strip ventilation defensive
What is a heat hole ?
Hole placed directly over the fire or as close as saftey permits
What is strip ventilation?
Strip ventilation extends the entire width of the building creating a fire break
Shall be done in conjunction with heat hole
What is a Center rafter cut?
Used when cutting plywood sheathing 4 cuts
Provides largest hole possible with minimal amount of cuts aids in sheathing removal (louvering)
Can also be used when doing a strip on 1x4 1x6 sheathing
What is decking ?
The material used to compromise base and exterior covering of the roof
What is diaphragm nailing ?
Plywood the 8s’ crosses rafters the 4s are parallel to rafters so sheets are staggered like a brick or block wall
What is dicing ?
Dice cuts made parallel to rafters
Technique used to cut 1x4 and 1x6 solid spaces or diagonal sheathed roofs
What are H clips ?
Used to hold the butted ends of plywood together commonly used in pitched roofs
What is a head cut?
Cut through the roof decking perpendicular to rafters
What is head cut used for ?
It’s used to locate rafters
What roofs must a head cut be done on?
Plywood and diagonal sheathing
What is j hook?
Bringing pick of axe in smooth forceful motion under and up decking near the rafter to remove decking material
What is a kerf cut ?
Single cut made thru roof decking the same width of chainsaw blade
Can be used as smoke indicator but not as effective
What are laddering principles?
Uninvolved corners of structures
Preferable to wind at your back
Minimum of two ladders thrown to involved structure
What’s a louver?
Louver plywood after 4 cuts push down with rubbish hook near the side closest to ladder and pull on far side
What are nailing blocks?
2x4s usually laid flat between rafters to nailing surface
Usually found every 4 feet
What is a parallel cut?
A cut parallel thru decking parallel to the rafters
What’s a penthouse door?
A door leading from interior stairwell of roof
What is a plug cut ?
A small triangular piece removing of Comp to expose sheathing type and Comp thickness
What is a score cut?
A light cut of roof covering (Comp)
To facilitate removal of multiple layers of Comp
What is a skim cut
A light cut cutting thru roof covering and plywood sheathing skim top of rafters
Used when louvering off purlin
What are skylights made out of ?
Glass or plastic
Where are skylights located on apartment buildings?
Over hallways and stairways
Where are skylights places in commercial buildings?
Placed over manufacturing areas
What’s a smoke indicator hole?
Small triangular hole thru roof decking made with chainsaw or axe
What is smoke indicator hole used for ?
Smoke conditions directly under smoke indicator hole
How should smoke indicator holes be placed ?
Along path of access or egress every few yards
When placed in working area what are smoke indicators good for ?
To see change in conditions which can be vital for safety of roof team
True or false placing smoke indicators on roofs attached to fire buildings can indicate interior exposure
True
Strip ventilation acts as a
Firebreak
Narrow section of roofing material usually performed across the width of the roof from parapet to parapet
How much more effective are turbine ventilators when spinning?
30%
What are bent pipes made out of ?
Abs plastic cast iron and steel pipe
Which way do vent pipes travel in building ?
Vertically
What are growing vent pipes ?
Indicator that roof has dropped or sagged
What is a 45 degree cut ?
Series of two cuts identify rafter direction ONLY
1st 45 degree cut toward or away from exterior wall
Make sure it intersects a structural member hit a rafter stop
2nd cut make perpendicular to exterior wall
What’s a 45 degree inspection cut?
1st cut 45 degree toward or away exterior wall when hit a rafter roll it 6-10 inches
Complete by removing a small triangle over structural member (rafter)
What is 45 degree inspection cut used for ? (4 things)
1 identify rafter type and direction
2 type of sheathing
3 thickness of Comp
4 smoke indicator hole
What are the benefits of dicing?
It’s directional team work back towards ladder
And after chain saw operator makes 3rd cut the puller can start pulling boards and operator can continue cutting
How is the length of dice cut determined ?
The length of pulling took picke head axe vs rubbish hook
True or false When dicing you can span two rafters
False if this happened the material can be difficult to pull
True or false you can dice twice in between rafters?
False material will fall and possible cause injury to interior firefighting crews
Always leave a minimum of _____ pull section between puller and cutter
1
Cut inside purlins _____ to avoid hitting metal hangars
4-6 inches
