What does VENTILATION do?
Facilitates rapid rescue, eliminates dangerous backdraft conditions, prevents flashover, curtails fire extension, and generally mitigates adverse fire conditions for the protection of both occupants and firefighters.
Introduction of oxygen to a confined space that is pressurized with heat, flammable gases that are deficient in oxygen, thereby resulting in an explosive force.
The simultaneous combustion of the combustible substances in a room heated to their ignition points.
Define VENTILATION? (As applied to Fire Service)
The systematic clearing from a structure, vessel, or other area of objectionable smoke, heat, or noxious gases through controlled channels, followed by the replacement of cooler air, which facilitates other fire fighting priorities.
Carbon Monoxide Explosive Rangeand Ignition Temp?
12.5% - 74% by volume.
Characteristics that indicate a BACKDRAFT CONDITION?
Smoke under pressure.
Black smoke becoming dense and grey-yellow.
Confinement and excessive heat.
Little or no visible flame.
Smoke leaving building in puffs or at intervals.
Sudden rapid movement of air inward when an opening is made.
(Inside) heavy swirling volume of smoke with whistling sound of air being drawn in.
(Outside) Very hot windows/ doors with puffing smoke.
Ventilating For BACKDRAFT?
Charged line ready at vent hole.
Indirect attack before entry. (Over pressurize room with steam to force products of combustion out of vent opening)
Difference between FLASHOVER & BACKDRAFT?
Amount of O2 present.
1. Size, extent, and location of building and the fire.
2. Life hazard.
3. Kind of material burning.
4. Susceptibility of the material to smoke, heat, and water damage.
OFFENSIVE Ventilation? Vent for?
Venting for FIRE. Ventilating CLOSE to the fire in order to:
have direct effect on fire itself
limit fire spread
make conditions safer for firefighters
DEFENSIVE Ventilation? Vent for?
Venting for LIFE. Ventilating AWAY from the fire or AFTER the fire is out to:
have effect on hot gases and smoke
improve access and escape routes
control smoke movement away from areas of building that are not involved.
Rule of Thumb for venting? (Life vs. Fire)
If venting for LIFE, vent as quickly as possible.
If venting for FIRE, wait until attack crew is ready with charged line.
Building type and design are 2 major factors to consider in determining ventilation. Other factors include?
1. Location and size of doors, windows, or other openings in walls.
2. Building size, height, number of stories, staircases, elevators, ducts, and roof openings.
3. Use and occupancy of building.
4. Basements and windowless buildings.
5. Involvement of exterior fire escapes and other exposures.
6. Presence of HVAC.
VERTICAL Ventilation (Opening roof) Safety Precautions?
Provide secondary means of egress.
Charged line in place.
DO NOT walk on spongy or springy roof.
CAUTION working around electric wires.
Stand to WINDWARD side of cut.
Watch for personnel within range of swing of axe.
Factors the can DESTROY the effectiveness of ventilation are?
Improper use of forced ventilation.
Breakage of glass.
Improperly directed fire streams.
Breakage of skylights.
Burn through that creates additional openings.
HORIZONTAL Extension occurs as a result of?
Direct flame contact.
Radiated heat or air convection.
Conduction of heat.
Define NATURAL Ventilation?
The techniques of VERTICAL and HORIZONTAL Ventilation when they are NOT assisted by MECHANICAL means.
Define FORCED (Mechanical) Ventilation?
Ventilation is accomplished by mechanical blowers or fans.
Advantages of FORCED Ventilation?
Ensures more positive control.
Supplements natural ventilation.
Speeds removal of contaminants.
Allows rapid rescue onder safer conditions.
Makes horizontal ventilation more effective.
Reduces need for vertical vent.
Less affected by erratic wind.
Reduces smoke damage.
Promotes good public relations.
Disadvantages of FORCED Ventilation?
Requires use of mechanical device, power source, and additional FF's.
Can increase intensity of fire.
Requires a large fan or number of smaller fans.
Provides limited air flow in defensive ventilation.
2 Techniques of FORCED Ventilation?
1. Positive Pressure
2. Negative Pressure
Critical requirements BEFORE implementing PPV?
Establish an exhaust opening 3/4 to 1 3/4 the size of intake.
Establish a clear channel from point of entry to exhaust.
Determine location of fire.
Position attack lines including exposure protection at exhaust opening.
Notify IC and any interior crews.
PPV should NOT be initiated when?
Signs of backdraft are apparent.
Dust or powders may be disturbed.
Fire location has NOT been established.
Fire is known to be spreading beyond origin.
A common attic exists in multiple occupancy building.
RAMFAN (gas) Output?
12000 ft3/ min
HIGH Alarm >= 50 ppm Source Identified
Evacuate and vent
HIGH Alarm >= 50 ppm Source UNIdentified
Evacuate and contact HazTech
LOW Alarm 25-50 ppm
Consider evac, identify source and vent.
Vent and identify source.
>= 12 ppm
Evac small children, pregnant women, seniors, and anyone with reps. problems. Identify source.
3 drawbacks to Forced Ventilation using a FOG STREAM?
Increase in amount of water damage.
Drain on available water supply.
More ice in freezing temps.