13 Verical Ventilation Flashcards
The preferred location for vertical venting is directly over seat of fire, but only if
It is judged to be a safe place
Before stepping onto any roof firefighters should first
Read the roof- the condition of it
Sound the roof- test its condition
And continue to do so as you move along it
If smoke or darkness makes roof reading difficult, what can be used to aid
Thermal imager
Every roof should be sounded with a hand tool except
A slate roof
Firefighters should leave the roof when
Vent is complete or conditions become unstable or dangerous
Primary hazard with vertical vent
On high steep surfaces with slip and fall hazard
Voltage of roof top solar panels
Up to 600 volts and 8 amps
When firefighters are on a roof the building should be laddered on how many sides
At least two, but on all sides if resources permit.
If ladders cannot reach the roof what methods should be used to gain access
Interior sitar ways,
exterior fire escapes
Adjoining buildings
To read a roof means
To observe the conditions of it, construction features and other indicators to unsafe conditions.
Roof conditions can be read from a position of safety such as
A parapet wall or aerial device
Things to be read of the roof before stepping onto it are
Age
Type of roof structure
Location and orientation of roof support members
Type and condition of roof coverings
Heavy tanks, machinery, solar, other loads
Visible smoke or fire
Skylights and vents can offer insight to the location of rafters or joists because
They are positioned between them.
Weathering of roof surface over time can reveal what
The rafter locations and how they are oriented
Thermal imagers can be used to identify what on the roof
Hot spots and rafters
Specific roof hazards to look for on a roof before stepping on, that indicate possible stability issues
Sagging roof surface
Roof vents are unusually tall (indicates sagging roof)
Large puddles of water
Smoke from roof vents
Heavy dead loads
Drop offs from light wells or varying roof elevations
Solar panels
If a roof is unstable vertical vent efforts may have to be done while working off of a
Aerial device
Sounding of a roof should be done with
The blunt end of a pike pole, rubbish hook, or axe head
In poor visibility, probing a roof surface can also reveal
Solar panels, vegetation, features, holes
A roof will sound
Hollow between rafters and solid over them, bounce in void space, and less so over rafters.
Roofs that have what, may not provide clear indications when sounded
Several layers of shingles or roof coverings
Roofs covered with slate or tile cannot be sounded, they must be
Have sections removed to reveal and inspect the surface
Ladders for roof access should be placed away from
Windows and wires, windows may vent fire and damage ladders or cut off escape
While on the ladde, one hand should sound with a tool while the other
Holds onto the ladder
Firefighters should walk only over that while on roofs
Structural members.
Poles on a roof should be made from what area to the other
Uninvolved toward involved
In relation the the hole and egress, firefighters should work or position themselves where
Firefighters should be between involved area and egress
If walking the ridge of a peaked roof, firefighters should walk how
With one foot on either end of the ridge pole
The strongest points of any roof are where
The roof meets the exterior walls
Directly over roof supports
At ridges or valleys
The weakest part of a roof is where
Between supports
Firefighters should never jump onto a roof because
They may fall through a weakened surface from weight on a single point or shock load cause structural failure
Roof ladders should not be used on weakened roofs, there are only used for
More secure footing on pitched roofs
Ideally, roof operations are done with the wind in what direction
At the firefighters backs
If the seat of the fire is on the windward side it may push fire and smoke toward roof crews, in this case what may be needed
A charged hose line on the roof.
Pertinent safety info for using a hose line on a roof
Wind direction and intensity Size of roof Type of roof covering. Time needed to vent Time needed to deploy hose Additional ffs needed for the hose
A hose line may not be needed on a single family home because the operation can be done and exited form quickly, however it may be needed on
An industrial or commercial roof, large area building
A hose line on a roof can be used for extinguishing
Spot fires on combustible roof surfaces
If a hose stream is needed to direct a thermal column from a vent opening on a roof the stream should be positioned how
Horizontally across it or at a slight upward angle but never directly into it.
While firefighters first test a roof surface by bouncing on it or sounding with a tool they should maintain
Contact with the ladder
While operations or moving along a roof firefighters should sound continuously and also stop occasionally to
Bounce on it and see if feeling has changed
The location for ventilation exit openings will generally be determined by several factors like
Layout of building Coordination with interior crews Initial size up of situation Smoke coming from existing openings Smoke or fire coming from roof coverings Blisters in covering Sagging roof
Casters are usually spaced
12-24 inches apart on center, spanning shortest distance form bearing walls
If direction or location of rafters is unknown and unable to be determined, what method wil find them
Make a diagonal 45* cut toward any exterior wall until a rafter is hit. After about three feet it is likely to hit one. If stiff unknown make a cut parallel with exterior wall for 2-3 ft. If no rafter is it it is presumed the fosters move parallel with the second cut.
Following precautions to be considered when venting a roof
Know the location of emergency exit points
Use existing openings if appropriate to minimize damage
Keep safe distance form cutting tools in use
Do not make holes between ff and escapes
Don’t cut rafters
Begin vent on leeward side moving back toward the wind
Remove ceiling below if possible
Get off once done
A distance of what is recommended from anyone using a cutting tool on a roof
10 ft in all directions, unless being used as a guide or back up.
Most common cutting tools for vent
Rotary, chain saw, pick head axe
Shuffle step
Method of keeping both feet on the roof of all times
Before and during the actual opening of the roof, the following items must be considered
Verify attack lines are charged and rdy
Evaluating roof construction type and condition
Providing secondary means of egress to roof
Observing weather, temp, humidity, wind speed and direction
Note any obstructions or dead loads on roof
Locate seat of fire
Reading the roof continually
Use existing openings when appropriate
Cut one large hole instead of several small
Enlarge opening instead of making more
Tracking time of incident
Because of its versatility and safety when used by a well trained operator, what is the preferred cutting tool in roof ops
Chain saw
Before using the chain saw, what must be checked to be working
Chain oiler
Citing a roof with a chainsaw, the bar is used how
The bottom of the bar cuts, just the tip of the bar, not the heel like for large members
Cutting off the roof surface with a pick head should be done as close to the rafters as possible to prevent
Deflection of the roof surface (bounce)
Another use for a pick head on the roof is
Scraping away roofing materials and pea gravel
The axe should be used with short cutting strokes to the side of the ff feet, not
Not between the feet
With roofs covered in shakes or shingles, it is more efficient for firefighters to cut the roof with an axe if
The shingles are scraped off first
When stripping decking off s roof after being cut, it is done by
Using a hook or pick head and inserting it into the leeward cross cut and pulling back toward the ff, while standing on the side of the hole
A sledge hammer or flat head axe can be used on what type of roof
Slate or tile roof
Pitch of a roof is expressed in
Inches of fall per horizontal foot, 12” out from roof at 90, how many inches down 12/12 is a 45 pitch
Most common roof pitch in milder climates
5-12
Stick built pitched roofs in residential construction are typically made of rafters at what size
2x6
2x4 trusses
Spaced 16-24” on center
Mono pitch trusses
Truss with lonely one angle, one support web in the middle. More prone to failure than conventional truss. Used for a shed style roof
Bridge truss
Mansard shaped. Diagonal wooden web members in one direction with vertical metal tie rods joining the webs. Trusses are often 2x12, joists usually 2x6-8. Spaced 16-20 feet
Likelihood of collapse is dependent on
Dimensions of material used
Unsupported distance
Live and dead loads
Duration of fire exposure
Pitched roofs can be a hazard even when dry because of
Gravel texture of asphalt shingles, loose tiles or shingles,
On metal decked roofs it may be possible to remove an entire panel by
Prying at the edges or removing screws and nails
To allow drainage, flat roofs often have what type of pitch
2-12 front to back for drainage
Space between a flat roof covering and ceiling below is called
Attic
Cockloft
Crawl space
Interstitial space
Inverted roof
Structural members below the top roof surface, ceiling attached to that, framed space above them to roof surface.
Roofs sheathed with planks are easier to strip but harder to
Louver or trench cut
Because lightweight concrete roofs are hard to breach they are often provided with
Knockout or removable panels for access
Generally the fastest and most practical way of venting a concrete roof is
Using existing openings like bulk heads, skylights, scuttles, ventilators
Poured gypsum roof
Gypsum is poured over gypsum board, with wire mesh re enforcement up to 2.5 inches thick
Modern mansard roofs are typically supported by what type of structural member
Bridge trusses
Wooden or metal access ladders built into the side of a building leading to the roof should not be used because
Age and weathering may have made them unstable and unsafe
Modern mansard roofs
Steep side walls to the roof facing out, almost vertically with shingles on it, flat or depressed top to the roof, sometimes depression is several feet down like a 360 parapet
Security measures found on flat roofs
Razor wire or razor ribbon, guard dogs
Parapet walls can help firefighting safety by
Preventing accidental walk off, hinder fire spread to exposure
Currently existing openings should be used with discretion because
They may not be placed directly over the fire, causing fire to be drawn, sprinklers activate and hinder venting,
Vent holes in flat roofs should be cut in reference to the rafters by
Being parallel to rafters and perpendicular to outside walls
First cut in a vent hole should be made on what side
Leeward side, subsequent cuts being made back to the windward side
Louder vent openings are cut over
One rafter to hinge off. Aka center rafter cut
Smoke venting under pressure from a turbine vent indicates the vent should be
Left alone, more efficient venting with rotary vane in place.
Roof monitored should have what removed to increase their vent efficiency
At least two sides
Skylights should be removed rather than
Broken
If a skylight needs to be broken it should be done how
Break a single pane first, and pause for interior crews to move out of the way.
Bowstring arch vs truss
Arch uses steel tie rods instead of bottom chords. Located from outside by wall plate or star.
Truss less arch roof
Massive arches of steel concrete or wood, buttressed at the ground at their ends. Purlins connect the arches and run perpendicular.
The single biggest hazard of arched roof is
Danger of sudden and total collapse
Hip sections of a arched roof may push out and collapse if
The roof fails or collapses
Panelized roofs
Laminated beams of various sized, but typically 6x36” span entire length or width supported at the end by pilasters, wooden or steel posts, or saddles in the wall
Pilasters
Rectangular masonry column built into a wall
Bridging effect of parallel chord trusses causes the top and Bottom chords to be under what type of force
Top under compression- supported by wall
Bottom under tension- unsupported
Gang nails or gusset plates typically only penetrate the wood how deep
3/8” deep
Wooden / metal bar joists have wooden top and bottom chords with 1” tubular rolled steel as the webs. They are normally spaced how far apart
2’
Steel trusses are aka
Bar joists.
In pitched wood framed roofs with truss construction, spans up to what are possible using 2x4 trusses
Up to 55’
Most common spacing for wooden pitched roof trusses is
2-4’
Common spacing for wooden I beams is
2’
Most common coverings for pitched roofs
Wood shakes Composition shingles or rolled roofing Ceramic or clay tile Slate Light gauge metal or Fiberglas
Most common coverings for flat roofs
Tar and gravel
Urethane/ isocyanate foam
Synthetic membrane
Metal
Shakes and shingles can be attached by
Nailing to 1x4 or 1x6 planks spaced apart by about 1” with tar paper over it. This allows sheathing to be removed by finding the space between planks and pulling shingles away by yanking parallel to the plank.
Cutting through multiple layers of composition roofing and shingles can be difficult with a chainsaw because
The multiple layers of asphalt shingles act cause it to gum up in the blade
Tar and gravel roof
Tar paper is layer over planking or plywood decking, hot tar is mopped over the paper, pea gravel is poured over it. Common for flat roofs
Urethane and isocyanate foam roofs are applied in two forms
4x8 sheets
Foamed in place
Single ply and synthetic membranes on roofs are easy to cut but dangerous because
They are highly combustible and release toxic gasses when burned
To reduce damage on tile roofs, firefighters should
Work on a roof ladder and step on the lower half of the shingle
Ideally state and tile shingles should be removed and
Stacked not broken
Two common types of steel clad roofs
1/4 x 2” steel straps laid out in grid form and welded together leaving square openings between them about 6-8” big. System is lag bolted down to decking or joists and then tarred.
4x8’ sheets of 1/8-1/4” steel laid down and welded at ends. Then tarred
For a steel clad roof, a 1/4 inch thick steel sheet weighs 19 lbs per square foot. A 20x50 roof would now have nhow much added weight
Appx 10,000 lbs
Square or rectangular hatches that access roof from attic or cockloft, accessible by ladder from top floor
Scuttle hatch
Penthouses (bulk heads)
Enclose a stairway and door on a roof,
A skylight should be removed by forcing the frame off at the flashing on all four sides, or three sides and using the fourth as
As a hinge
Monitor vents
Like a dog house. Square or rectangular over a roof to provide extra light or venting. May have metal. Wired glass, glass, louvers.
Except for the need to occasionally break windows, light shafts generally do not need
Opening or enlarging for tactical vent
Removing ridge vents may not provide an adequate opening for vent and will need
Conventional venting efforts to enlarge
Clerestory windows
Narrow horizontal windows on a short vertical wall between two offset roof sections. Better to break than cut vent hole right above them
Type of cut that is often the fastest and most efficient
Louver vents
Knowing the location and direction of rafters and the type of sheathing are critical to
Safe and efficient roof cutting operations
Center rafter or cutting with the rafter method, is made by cutting
One cut across the center rafter and making the other side cuts between the void on either side, continuing the cuts in that sequence in a long narrow trench type parallel to the center rafter
Dicing method of louver vents, aka rolling the rafters
Long cuts make perpendicular to the rafters, cuts made parallel to the rafters in the void space to knock out multiple panels so they hinge in the middle on multiple rafters. 798 method
On a lightweight panelized roof, rolling back the roof is accomplished by
Using four firefighters two with chainsaws. Two with hooks, cutting the purlins or rafters and peeling back the material as the cuts are made back
Trench ventilation is aka
Strip ventilation
Trench cuts should extend from where to where
From outside wall to outside wall, end to end, of the building in the perpendicular direction to stop fire, 4’ wide, the flashing bent up or cut if needed. Center rafter cuts is the fastest.
