Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
32 Cards in this Set
- Front
- Back
|
Ventilation |
The planned, methodical and systematic removal of pressure, heat, smoke, toxic gases and flame from an area and the replacement of these products with cooler, fresh air |
|
|
Outside Fire |
-Heat and fire gases escape -Fuel is limiting factor |
|
|
Compartment Fire |
-Radiated heat absorbed by other materials -Smoke & hot air rise & transmit heat -Smoke also provides a fuel mixture -Oxygen is limiting factor |
|
|
Stages of a Compartment Fire |
-Incipient -Growth (flashover occurs just before fully development) -Fully Developed -Decay |
|
|
How does ventilation work? |
-Heat & smoke rise & create pressure. Path of least resistance. -Opening releases pressure, pulls heat, smoke and fire to opening.
Double edge sword- will eventually make fire worse. Must be coordinated with fire attack Poorly placed ventilation openings will pull fire toward them.
|
|
|
Reasons for Ventilation |
-Removal of smoke, heat & fire gases -Improved visibility, locate fire quicker -Reduced potential harm to victims -Reduced stress of firefighters -Assist with fire control & extinguishment -Localize fire -Removes trapped heat & smoke which help perpetuate the fire -Delays extreme fire behavior -Aids in property conservation |
|
|
Types of Ventilation |
-Self ventilation -Vertical ventilation -Horizontal ventilation Natural Forced - positive, negative, hydraulic
-Built-in ventilation systems
|
|
|
Self Ventilation |
-Fire has burned through the roof decking -Compromised roof structure, not safe to be on or under -This is cause to think about a transition to a defensive attack |
|
|
Vertical Ventilation |
-Most effective avenue to exhaust smoke & fire gases -Natural convection currents utilized -Allows exhaust prior to entry of oxygens -Localizes fire -Opening roof at highest point above the fire |
|
|
Rules to Ventilate by |
-2 Escape routes at strong points of roof -Full PPE including on air - Hose line to the roof - Read roof as you approach -Sound roof on and off -Travel on strongest parts of roof -Coordinated with attack team -1 Large hole better than multiple small holes 4x4' min for residential 8x8' min for commercial -Cut with wind to your back -Work toward your ladder |
|
|
Vertical Ventilation Technique (4 Holes) |
-Heat hole -Directional hole -Inspection hole -Trench cut (strip ventilation) |
|
|
Trench Cut |
-Defensive operation -Writing off a portion of the building -Hoselines need to be in place to defend this trench -Nobody inside the fire side of the trench |
|
|
Horizontal Ventilation |
-Venting through windows and doors Used when -Smaller fires that don't require vertical vent -Buildings that cannot be vertically ventilated easily such as high-rise, two story building with fire on 1st floor only and basement fires. -Compromised roof strucutre |
|
|
Horizontal Ventilation Types |
Natural Ventilation -Using wind to ventilate structure
Forced (Mechanical) Ventilation -Using fans, smoke ejectors or other means to push or pull smoke out of structure |
|
|
Natural Horizontal Ventilation Advantages |
-Quick to deploy -Minimal effort to conduct -Relatively safe |
|
|
Natural Horizontal Ventilation Disadvantages |
-Limited natural openings -May hinder access to openings -Does not fully use the natural flow of convection currents -May cause increase in fire spread -Can be affected by prevailing weather conditions |
|
|
Natural Horizontal Ventilation Technique |
-Open leeward side first at highest point -Open windward side next at lowest point
Remove screens if possible -Reduce airflow by 50% |
|
|
Forced Horizontal Ventilation Advantages |
-More positive control over fire -Supplements natural ventilation -Speeds removal of contaminants -Reduces smoke damage which increases good PR |
|
|
Forced Horizontal Ventilation Disadvantages |
-Introduces air in large volumes -Dependent on power source -Requires special equipment |
|
|
3 Types of Forced Horizontal Ventilation |
Hydraulic ventilation - nozzle needs to be 2ft away from opening & 85-90% of fog covers opening
Negative pressure ventilation Positive pressure ventilation |
|
|
Hydraulic Ventilation |
Type of Forced Horizontal Ventilation -Nozzle flowing 95gpm moves 5000 CFM -Used to clear a room of smoke, heat, steam and gases after fire control -Uses air movement of a fog stream to draw out products of combustion -Very effective quick technique for clearing fire room |
|
|
Hydraulic Ventilation Disadvantages |
-Increased water damage -Drain on available water supply -Firefighters must be exposed to environment -Operation interrupted when air supply for firefighters runs out |
|
|
Negative Pressure Ventilation |
-Uses smoke ejectors to create negative pressure in a building & pulls smoke out -Place fan so they exhaust with wind not against -Keep flow as straight as possible, every corner causes turbulence -Seal opening around ejector to avoid churning |
|
|
Negative Pressure Ventilation Disadvantages |
-Personnel subjected to atmosphere while setting up -Contaminates drawn through ejector -Doorways/windows obstructed -Rarely used -1/2 as effective as Positive Pressure Ventilation |
|
|
Positive Pressure Ventilation |
-Use high volume fan to create higher pressure in building -Equally effective with horizontal or vertical -Pressurizing small areas one at a time, controlled by opening or closing doors & windows. -Cone of air must cover open entirely -Can use two or more fans parallel or in series -Maintain one exit point at a time -Exit should be same size or smaller than entry point to maintain positive pressure effect |
|
|
Positive Pressure Ventilation Advantages over Negative Pressure Ventilation |
-Firefighters not exposed to environment -Fans not directly blocking ingress or egress -Twice as effective as NPV -Contaminates not drawn through ejector |
|
|
Built-in Ventilation Systems |
-System may automatically shut down when smoke or heat is detected in the air ducts or firefighters may have to shut down the system -Heating, ventilating and air-conditioning (HVAC) systems may draw in smoke and heat and spread fire -System may be equipped with dampers or smoke detectors which shut system down if smoke is present -FFs should not attempt to operate smoke control systems during fire conditions -Building engineers should be called to operate smoke control systems at direction of fire personnel |
|
|
Ventilation Problems - High-Rise Buildings |
High-Rise Buildings -stack effect may spread smoke to multiple floors -4 to 6 times as much staffing as residential -Ventilate utilizing a stairwell with roof access hatch -Make sure roof access blocked open or removed -All doors unlocked or stop-locked -Not simultaneous with evacuation in same stairwell |
|
|
Ventilation Problems - Basements |
-Access to a basement is extremely difficult without effective ventilation -Must descend through the heat & gases -Limited openings with which to ventilate -Hard to access & possibly deep seated fires due to use as storage |
|
|
Ventilating Basement Fires |
-Must be coordinated with attack crews -Utilize exterior basement windows opposite the attack -If no exterior windows or doors, consider vent hole in 1st floor near a window |
|
|
Why is ventilation more important now than ever? |
Construction -Increased synthetics -Increased air tightness -Increased fire load
Equipment -Better turnouts -Better airpacks |
|
|
Properly done ventilation can..? |
-Decreases fire spread & increases visibility for fire attack -Aids in life safety -Speeds fire attack -Aids in fire spread control -Reduces flashover & backdraft potential -Helps with property conservation |
