VENTILATION

The systematic removal of heated air, smoke, and gases from a structure and replacement

with cooler, cleaner air

TS 10–1

TYPES OF VENTILATION

• Vertical – Trench (strip)– Basement

• Horizontal – Natural– Forced

• Mechanical positive-pressure• Mechanical negative-pressure• Hydraulic

TS 10–2

WHY VENTILATE?

• Aids in saving lives

• Aids in suppressing fire

• Aids in reducing property damage

TS 10–3

TODAY’S INCREASING NEED FOR VENTILATION

• Increased fuel load in all occupancies due to increased use of plastics and other synthetic materials

• More products of combustion

• More dangerous products of combustion

• “Tighter” homes making heat retention greater– Increased insulation– Energy-saving glass– Vapor barriers

TS 10–4

ADVANTAGES OF VENTILATION TO RESCUE OPERATIONS

• Improves visibility

• Allows for faster location of unconscious victims

• Simplifies and expedites rescue

• Makes conditions safer for firefighter and victims

TS 10–5

ADVANTAGES OF VENTILATION TO FIRE ATTACK & EXTINGUISHMENT

• Removes smoke, gases, and heat from building

• Facilitates entry of firefighters

• Reduces obstacles that hinder firefighters

• Increases visibility for quicker location of seat of fire

TS 10–6

ADVANTAGES OF VENTILATION TO FIRE CONTROL

• Reduces mushrooming

• Reduces flashover potential

• Reduces backdraft potential

• Controls fire spread

TS 10–7

ADVANTAGES OF VENTILATION TO PROPERTY CONSERVATION

• Permits rapid extinguishment

• Reduces water, heat, and smoke damage

• Confines fire to an area

• Allows salvage operations and fire control to take place concurrently

TS 10–8

BACKDRAFT INDICATIONSVS 10-2

PuffingSmoke

Black SmokeBecoming Dense

Yellow-Gray

Walls TooHot to Touch

Dull Orange Glowof Visible Fire

PressurizedSmoke Coming

From SmallCracks

Darkened Windows

Rattling Windows

Hot UnbrokenGlass

BACKDRAFT PREVENTION

Top (vertical) ventilation is the primary method

of preventing backdraft.

TS 10–9

LIFE SAFETY HAZARDS IN UNVENTILATED BUILDINGS• Obscurity caused by dense smoke

• Presence of toxic gases

• Lack of oxygen

• Presence of flammable gases

• Danger of backdraft

• Danger of flashover and rollover

TS 10–11

FACTORS DETERMINING HORIZONTAL OR VERTICAL

VENTILATION • Building type and design

• Number and size of wall openings

• Number of stories

• Number of staircases, shafts, dumbwaiters, ducts, roof openings

• Availability of exterior fire escapes

• Exposure involvement

TS 10–12

VENTILATION PROBLEMS: BASEMENTS

VS 10-4

• Need to Descendthrough Heat andSmoke

• Blocked or Secured Outside Entrances

• Difficulty of UsingNatural Ventilation

VENTILATION PROBLEMS: WINDOWLESS BUILDINGS

VS 10-5

• Late Detection DelayingVentilation and Creating Backdraft Conditions

• Horizontal VentilationDifficult or Impractical

• Usually Require Mechanical Ventilation

VERTICAL FIRE EXTENSION

Opening for ventilation purposes before the fire is located may spread the fire to areas

that otherwise would not have been affected.

TS 10–13

VENTILATION OPENING LOCATION & SIZE FACTORS

• Availability of natural openings

• Fire location

• Building construction

• Wind direction

• Fire phase

• Building condition

• Building contents

TS 10–15

• Roof type and condition

• Effects on fire

• Effects on exposures

• Attack crew’s readiness

• Ability to protect exposures

• Size

VERTICAL VENTILATIONVS 10-6

Roof Opening(At least 4’ x 4’[1.2 m x 1.2 m])

VERTICAL VENTILATION

Opening the roof or existing roof openings to allow heated gases and smoke to escape

to the atmosphere

TS 10–16

PRE-VENTILATION SAFETY PRECAUTIONS

• Consider type of building involved.

• Consider location, duration, and extent of fire.

• Observe safety precautions.

• Identify escape routes.

• Select place to ventilate.

• Move personnel and tools safely to roof.

TS 10–17

ROOF TYPESVS 10-7

FlatMansard

Shed

ButterflyHip

Gable

Lantern GambrelArch

BASEMENT FIRES

• First extension commonly into the attic

• May be ventilated in a variety of ways:– Horizontal ventilation through ground-level

or below-ground windows – Through interior vertical shafts (stairwells,

hoistway shafts, etc.)– Mechanical ventilation through a hole in the

floor near a ground-level door or window

TS 10–29

ELEVATED STREAMS

• Can force air and gases back into building if not used properly

• If projected just above the horizontal plane, are effective in subduing sparks and flying brands rising from ventilation opening and in reducing heat of thermal column

• Should never be projected through the ventilation hole while firefighters are still inside building

TS 10–30

VENTILATIONVS 10-13

Correct Application

Incorrect Application

FACTORS THAT CAN DESTROY VERTICAL VENTILATION

EFFECTIVENESS• Improper use of

forced ventilation

• Excess glass breakage

• Fire streams directed into ventilation holes

• Skylight breakage

TS 10–31

• Explosions

• Burn-through of the roof, floor, or wall

• Additional openings between attack team and upper opening

HORIZONTAL VENTILATIONVS 10-14

Windward

Wind Direction

Leeward

Fresh Air

HORIZONTAL VENTILATION

Venting of heat, smoke, and gases through wall openings such as windows and doors

TS 10–32

HOW HORIZONTAL FIRE EXTENSION OCCURS

• Through wall openings by direct flame contact or by convected air

• Through corridors, halls, or passageways by convected air currents, radiation, and flame contact

• Through open space by radiated heat or convected air currents

TS 10–34

• In all directions by explosion or flash burning of fire gases, flammable vapors, or dust

• Through walls and interior partitions by direct flame contact

• Through walls by heat conduction through beams, pipes, or other objects that extend through walls

HORIZONTAL EXTENSION KEY POINTS

• Wind is helpful but too much wind can be detrimental.– Windward — Side of building the wind is striking– Leeward — Opposite side of building

• Horizontal ventilation may block escape of occupants.

• There is an ignition hazard to higher portions of the fire building posed by rising heated gases.

TS 10–35a

HORIZONTAL EXTENSION KEY POINTS (cont.)

• Do not open building until charged lines are in place at attack entrance point, where fire might be expected to spread, and in positions to protect exposures.

• Take precautions against upsetting horizontal ventilation.– First open a door on leeward side to create a normal

process of thermal layering.– Know that opening doors between fire fighting crews

and exit point reduces intake of fresh air.

TS 10–35b

UPSETTING HORIZONTAL VENTILATION

VS 10-15

FORCED VENTILATION

Ventilation accomplished mechanically (with fans) or hydraulically

(with fog streams)

TS 10–36

PORTABLE FAN SAFETY MEASURES

• Shut down before moving.

• Carry by handles.

• Clear personnel from area before starting.

• Do not place where clothing, draperies, or curtains can be drawn into fan.

• Avoid the discharge stream: heat and particles may be projected by venting equipment.

TS 10–37

ADVANTAGES OF FORCED VENTILATION

• Ensures more positive control of fire

• Supplements natural ventilation

• Speeds removal of contaminants

• Reduces smoke damage

• Promotes good public relations

TS 10–38

DISADVANTAGES OF FORCED VENTILATION

• May cause fire to intensify and spread

• Depends upon a power source

• Requires special equipment

TS 10–39

TYPES OF FORCED VENTILATION

VS 10-16

Positive Pressure Horizontal Mechanical Hydraulic

FORCED VENTILATION MECHANICAL NEGATIVE PRESSURE

VS 10-17

Wind DirectionIntake

Opening(Optional

In-BlowingEjector)

Draft Path

Pressure Inside BuildingLower Than Outside Building

Smoke Ejector

(Exhaust)

Salvage CoverOr Tarp

BlockingOpening

Around Ejector

Closed Doors

FORCED VENTILATION MECHANICAL POSITIVE PRESSURE

VS 10-18

ClosedDoors

High Power

Fan

ExitOpening

(Same Size AsEntry Opening)

Draft Path

Pressure Inside BuildingHigher Than

Outside Building

Cone CoveringEntire Door

Opening

ADVANTAGES OF MECHANICAL POSITIVE-PRESSURE

VENTILATION• No need to enter smoke-filled environment

• Effectively supplements both horizontal and vertical ventilation

• Allows for efficient removal of smoke and heat

• Does not effect building contents or smoldering debris

• Is faster than negative-pressure ventilation

TS 10–40a

ADVANTAGES OF MECHANICAL POSITIVE-PRESSURE VENTILATION (cont.)

• Does not interfere with ingress or egress

• Is easier to clean and maintain positive-pressure than negative-pressure fans

• Is applicable for all types of structures

• Allows for directing heat and smoke away from unburned areas or paths of exit

TS 10–40b

DISADVANTAGES OF MECHANICAL POSITIVE-PRESSURE VENTILATION

• Requires an intact structure

• May increase interior levels of carbon monoxide

• May extend hidden fires

TS 10–41

GUIDELINES FOR EFFECTIVE POSITIVE-PRESSURE VENTILATION

• Take advantage of existing wind conditions.

• Make certain that cone of air from fan covers the entire entry opening.

• Systematically open and close doors or increase the number of fans to reduce size of area being pressurized.

• Keep size of exit opening in proportion to the entry opening.

TS 10–42

FORCED VENTILATION HYDRAULIC

VS 10-19

Fog Stream(Covering 85% 90% of Opening

Nozzle Tip(At least 2 ft. [0.6m]Back from Opening)

HYDRAULIC VENTILATION• Typically used to clear a structure of heat, smoke,

steam, and gases following the initial knockdown of fire

• Takes advantage of air that is drawn into the fog stream to help push the products of combustion out of structure

• Fog pattern should be wide enough to cover 85 to 90 percent of the window or door opening through which the smoke will be pushed

• Nozzle tip should be no closer than 2 feet (0.6 m) from ventilation opening

TS 10–43

DISADVANTAGES OF HYDRAULIC VENTILATION

• May increase amount of water damage

• Will put a drain on available water supply

• In freezing temperatures, will increase ice in area surrounding building

• Requires nozzle firefighters to remain in heated, contaminated atmosphere throughout operation

• Operation may be interrupted if nozzle team has to leave the area

TS 10–44