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