FVCC Fire Rescue
Ventilation
Part B
Types of Ventilation
• Horizontal Ventilation: Use of doors and windows to ventilate across the
floor of a building. Especially, when there is not a roof directly above fire
floor.
• Opening doors/windows between advancing firefighting crews and
established ventilation points, reduces intake of fresh air from
opening behind firefighters
Types of Ventilation
• Horizontal
▫ Advantages
 Uses openings
 Uses natural air currents
▫ Disadvantages
 Depends on natural air currents
 Routing may expose other parts of the building
 Same routes used by ventilation may be used by occupants
escaping.
 Danger of released gases igniting higher portions of the
building.
Types of Ventilation
• Horizontal Ventilation: Open leeward side windows first
at top. If windward side is opened first, may pressurize
building upsetting the normal thermal layering.
• Open windward side windows next at bottom.
• Keep ventilation openings clear from obstructions.
• Performed on floor(s) above fire floor.
• Used mostly on multi-storied buildings.
• When would you use horizontal vent on a ranch house?
• Hint: (house has a basement)
•Horizontal
–Open building on leeward side
–Remove any obstructions
–Open building on windward side
–Remove any obstructions
Types of Ventilation
• Vertical Ventilation: Opening made above the fire
to relieve heat and gases due to mushrooming
Mushrooming: when heat, smoke & other gases accumulate
To the state in which they bank down & begin to spread laterally
To involve other parts of the structure. Caused by convection!!!
Types of Ventilation
• Vertical Ventilation: Ventilation opening should
be made directly over the fire and at the highest
point.
Types of Ventilation
• Vertical Ventilation: Utilize any natural openings
already in place, such as: skylights, scuttle holes, exhaust
fans, etc. These openings are faster to open than cutting
a hole .
When attempting ventilation through a roof monitor, if the monitor is
Not removable, 2 sides should be opened to create required draft.
Types of Ventilation
▫ Note the existence of obstructions or excessive
weight on the roof.
Types of Ventilation
• Vertical Ventilation: Ventilation openings should be
large enough
• (minimum of 4’ x 4’ ).
*Kerf cuts are small cuts (normally the
4 ft
4 ft
width of the saw blade) sometimes
Used to determine fire direction.
*Inspection hole is done by cutting a
Small triangle in the roof.
*Louvered cuts are made in between the
Rafters rather than beside the rafters
Causing the panels to be hinged.
Square openings help facilitate roof repairs (Customer Service)
Types of Ventilation
• Vertical Ventilation: Openings cut on pitched roofs
should be on the leeward side and as high as possible.
Wind
Observe wind direction in relation to exposure.
Work with wind at your back or side.
Types of Ventilation
• Vertical Ventilation: Make sure opening is clear from any
material or obstruction.
• Guard the opening to prevent personnel from falling into the
building.
Last step in roof ventilation is to open up the ceiling below the
Ventilation hole, with a pike pole or plaster hook.
Be aware that excessive glass breakage including skylights,
Explosions, additional openings between attack team & upper
Opening, improper use of forced ventilation, & burn through roof
Can destroy effectiveness of vertical ventilation.
Types of Ventilation
• Trench Ventilation (strip ventilation): Used in buildings
with large attic areas to stop horizontal spread of fire.
• Identify escape routes.
• Consider location, duration & extent of fire.
Good for venting small strip malls
Types of Ventilation
• Trench or strip
▫ Advantages
 Aids in stopping the horizontal spread of fire
▫ Disadvantages
 Must be cut well ahead of the advancing fire
 Must be a minimum of four foot wide and is timemanpower consuming
Types of Ventilation
• Trench Ventilation: 4’ wide opening cut in
roof from outside wall to outside wall.
Type of Ventilation
• Trench Ventilation: Opening must be far
enough away from fire to allow it to be
completed before fire reaches there.
Type of Ventilation
• Trench Ventilation: Tactic used to save rest of
structure by cutting fire break in roof.
Type
of Ventilation
• Hydraulic
Ventilation: Use of interior fog stream
to move smoke and gases through window or door.
Pressurized ventilation
Type of Ventilation
• Hydraulic
▫ Advantages
 May be used in situations other types are not
 Takes advantage of the air drawn into the fog stream.
▫ Disadvantages




May increase the amount of water damage inside the structure
Drain on the available water supply
Increase in the ice problem during freezing weather
Firefighters operating the nozzle must remain in the heated,
contaminated area
 Remain aware of conditions around you; can intensify fire in
surrounding area
 Operation may be interrupted when crew goes for fresh SCBA
bottles
Type of Ventilation
• Hydraulic
Ventilation:
Wide fog
pattern utilized
approximately
2 ‘ from the
opening.
2 ft.
Hydraulic
Ventilatio
n: Fog
pattern
must cover
85%-90%
opening for
maximum
effect.
Type of Ventilation
• Mechanical Ventilation
▫ Forced
 Prevents smoke from churning in the opening.
 Avoid blockage of the intake side of the ejector.
• Mechanical (forced)
▫ Advantages






Ensures positive control
Supplements natural ventilation
Speeds the removal of contaminants
Facilitates a more rapid rescue under safer conditions
Reduces smoke damage
Promotes good public relations
▫ Disadvantages
 Introduction of air can cause the fire to intensify and spread
 Dependent upon a power source
 Requires special equipment
Type of Ventilation
Negative Pressure: (Use
of smoke ejectors)
• Placement of ejector for
maximum effect (highest
point in the opening and on
leeward side of building if
possible).
• Place to exhaust is in same
direction as the natural
wind.
• Keep airflow in as straight a
line as possible
PROCEDURES
• Mechanical/mechanical pressurization (forced
ventilation)
▫ Negative pressure
 Place ejector in opening to exhaust in the same way
as the wind direction
 Cover the area around the ejector to prevent
churning
 Establish and maintain desired draft path
 Remove all obstacles
 Avoid blockage of the intake side of the ejector
PROCEDURES
▫ Negative pressure
 Place ejector in opening to exhaust in the same way
as the wind direction.
 Cover the area around the ejector to prevent
churning
 Establish and maintain desired draft path
 Remove all obstacles
 Avoid blockage of the intake side of the ejector
Type of Ventilation
• Reduce “churning” (cover area
around the fan with a salvage
cover)
• Remove items such as: drapes,
blinds, screens, etc. which
might block air flow.
• Provide and maintain
unobstructed replacement air
opening.
• Supplements natural
ventilation
• Speeds up removal of
contaminants, assisting in
creating a safer environment
• Promotes good public relations
Type of Ventilation
• Mechanical
Ventilation:
Caution: Improper
application of positive
pressure ventilation may
• Positive Pressure: (PPV Fans) increase fire spread and the
safety hazards.
• Placement of PPV fan for
maximum effect (outside –
ground level on windward side
of building). Placed a few feet
outside the door.
• Produce a cone of air to
completely cover door opening.
Have exit area same size as
opening.
• More efficient removal of
smoke & heat.

Type of Ventilation
• Mechanical Ventilation:
• Positive Pressure: (PPV Fans)
• Eject smoke from opening on opposite side of building (leeward
side).
• May pressurize one room at a time by closing interior doors.
• Speed up process by reducing size of area being ventilated by
systematically opening/closing doors.
• A window screen could reduce effectiveness by as much as 50%.
• Multiple story buildings point of entry is at the lowest point, point
of exit is at highest point.
• Do not block openings.
• For greatest efficiency, exhaust opening should be 75% to 150%
intake opening.
• Equally effective with Vertical or Horizontal Ventilation.
• Set without firefighters entering a smoke filled environment.
PROCEDURES
▫ Positive Pressure
 Place blower several feet outside the point of entry
 Check to make sure air cone completely covers the
opening
 Open the exit opening (75% to 150% of the entrance
opening)
 Systematically open and close doors within the
structure to exhaust the products of combustion.
Type of Ventilation
• Mechanical pressurization (positive pressure)
 Cleaning and maintenance of blowers usually reduced.
 System applicable to all types of structures.
 Heat and smoke may be directed away from unburned areas or
paths of exit
▫ Disadvantages
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May intensify and spread hidden fire.
Gas power may increase CO2 levels in building.
Noise affects communications.
Control of openings and pressure leaks.
Caution: Prior to using PPV, firefighters must be property trained and aware that if used
improperly, it can intensify and spread fire conditions. Refer to the PPV
fan manufacturer;s training program.