Ventilation The Basics'

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Ventilation The Basics.
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Objective

• The student will demonstrate the principles of
  ventilation, the safety precautions to be taken
  when ventilating a structure, and how to use the
  various types of ventilation through classroom
  participation and discussion.

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Enabling Objectives

• Discuss principles of ventilation
• Identify safety precautions that should be taken
  when undertaking ventilation operations
• Discuss different types of ventilation

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Principles of Ventilation
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What is Ventilation?

• The planned, methodical, and systematic removal
  of pressure, heat, smoke, toxic gases, and flame
  from an area through predetermined paths and the
  replacement of these products with cooler fresh
  air

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How does it work?

• Heat and smoke rise
• Path of least resistance
• Smoke moves horizontally and vertically
  mushrooming

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Why do we ventilate?

• Removal of smoke, heat, and fire gases
• Improve visibility
• Reduce potential harm to victims
• Reduce stress on firefighters
• Assist with fire control and extinguishment

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Advantages

• Increased visibility
• See the victim
• Find the seat of the fire
• Increased effectiveness of fire attack
• Reduced possibility of flashover or backdraft
• Aids in property conservation
• Small amount of ventilation damage results in
  larger reduction in overall fire damage

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Results Depend On

• Size and type of occupancy
• Extent and location of fire
• Whether fire is free-burning or smoldering

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Ventilation Concerns

• Fire travel by convection
• May cause exposure fires and additional fires in
  fire structure
• Improper ventilation may increase fire spread

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Safety Precautions
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Safety Precautions

• Always wear full PPE, to include SCBA
• Always vent at highest point possible
• Have hoselines in place to make interior attack
• Work with wind at back or side
• Never flow water into vent hole with personnel
  inside building
• Check roof stability before starting operations

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Safety Precautions

• Restrict number of personnel to minimum needed to
  accomplish task
• Work from roof ladder when cutting hole
• Watch out for overhead power lines
• Have secondary escape routes in place
• Check equipment before going on roof
• Do not cut main structural supports

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Safety Precautions

• Watch out for unsafe or deteriorating conditions
• Note and avoid any existing dead loads or
  obstructions
• Maintain communications
• Remove crew from roof when vent operations
  concluded

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Lightweight Construction

• Notify IC when lightweight truss construction
  found
• Avoid working around areas with roof mounted
  equipment
• Always expect imminent collapse when lightweight
  truss construction is being impinged by fire
• Work off of aerial ladders where possible

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Lightweight Wood Truss

• Engineered with lumber sized smaller than
  traditional dimensional lumber
• Accounts for over 60 of all new construction
• Very short life expectancy when exposed to fire

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Lightweight Wood Truss

• Held together with gusset plates instead of nails

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Backdraft

• Sudden violent reignition of a closed compartment
  fire when a new source of oxygen is introduced

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Backdraft Signs

• Smoke visible, but no flames
• Yellowish colored smoke
• Windows darkened over
• Smoke puffing from openings (breathing building)
• Smoke under pressure

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Rollover

• Smoke and fire gases advancing along a ceiling
  until stopped by walls

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Flashover

• The sudden rapid ignition of all contents of a
  room or area
• Seconds to escape

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Flashover Signs

• Rollover progressing close to floor
• Large amounts of flame and heat with little smoke
• Tunnel Effect

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What Can Go Wrong

• Fatality
• September 14, 2002
• A firefighter died after falling through roof
  while observing another firefighter conducting
  ventilation operations. The deceased firefighter
  was not wearing SCBA.
• Source NIOSH Fatality Assessment and Control
  Evaluation Investigation Report 2002-40

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What Can Go Wrong

• Near Miss
• March 1, 2003
• Firefighters were conducting search operations in
  low attic when one firefighter felt a jerk to his
  helmet. The firefighter immediately dropped to
  the floor and the interior crew exited the
  building. Observation of struck firefighters
  helmet revealed where chainsaw from vent
  operations struck him.
• Source National Firefighter Near Miss Reporting
  System Report 05-0000339

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What Can Go Wrong

• Near Miss
• January 13, 2007
• Firefighters were conducting trench ventilation
  operations on a church made from lightweight
  truss construction. Personnel were operating from
  an aerial ladder when 40 feet of roof collapsed,
  sending a 30 foot fireball into the sky.
• Source National Firefighter Near Miss Reporting
  System Report 07-0000726

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Ventilation Types
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Direction of Travel

• Horizontal
• Vertical

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Horizontal Ventilation

• Uses natural openings in occupancy
• Doors and windows
• Effective in basements and high rise structures

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Horizontal Ventilation

• Technique
• Open leeward side openings first, highest point
  possible
• Open windward side openings next, lowest point
• Coordinate openings used with Command
• Select openings used with future ventilation
  operations in mind

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Horizontal Ventilation

• Advantages
• Quick to deploy
• Minimal effort to conduct
• Relatively Safe

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Horizontal Ventilation

• Disadvantages
• Limited to natural openings
• Access to openings may be hindered
• Does not use natural flow of heat and smoke
• May change dynamics of fire attack
• May cause increase in fire spread
• Can be affected by prevailing weather conditions

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Horizontal Ventilation
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Vertical Ventilation

• Considered most effective avenue to exhaust smoke
  and fire gases
• Openings made above fire
• Highest point closest to fire

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Vertical Ventilation

• Technique
• Utilize existing openings first
• Consider using stairwells and shafts
• When creating opening, make one large opening
  rather than several small openings
• Get off roof when completed

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Vertical Ventilation

• Advantages
• Allows heat and smoke to follow natural movement
  pattern
• Best for reducing potential for backdraft
• Can assist in localizing fire due to ventilation
  hole placement

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Vertical Ventilation

• Disadvantages
• Time Consuming
• Inherently dangerous
• Equipment malfunctions
• Building construction

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Ventilation Methods

• Natural
• Mechanical
• Hydraulic

Be aware there are many methods of conducting
each type of ventilation technique- these will be
reviewed in depth later.
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Mechanical Ventilation

• Negative pressure
• Positive pressure

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Questions???