BOF FF1 Chapter 12*20 Tactical Ventilation

Downwind Side

Side of a building away from the wind, the low-pressure side.

Exhaust

In terms of ventilation, the location where hot gases and the products of combustion leave a structure.

Exhaust Opening

Intended and controlled exhaust locations created or improved at or near the fire to allow products of combustion to escape the building.

Exposures

Structures or separate parts of the fireground to which a fire could spread.

Horizontal Smoke Spread

Tendency of heat, smoke, and other products of combustion to rise until they encounter a horizontal obstruction. At this point they will spread laterally (ceiling jet) until they encounter vertical obstructions and begin to bank downward (hot gas layer development).

Hydraulic Ventilation

Ventilation accomplished by using a spray stream to draw the smoke from a compartment through an exterior opening.

Intake

In terms of ventilation, the location where air is being entrained toward a fire.

Kerf Cut

Single cut the width of the saw blade made in a roof to check for fire extension.

Louver Cut

Rectangular exhaust opening cut in a roof, allowing a section of roof deck (still nailed to a center rafter) to be tilted, thus creating an opening similar to a louver.

Mechanical Ventilation

Any means other than natural ventilation; may involve the use of fans, blowers, smoke ejectors, and fire streams.

Natural Ventilation

Techniques that use the wind, convection currents, and other natural phenomena to ventilate a structure without the use of fans, blowers, smoke ejectors, or other mechanical devices.

Negative Pressure

When pressure is lower inside a structure than outside the structure, causing fresh air from outside to move inside.

Negative-Pressure Ventilation (NPV)

Technique using smoke ejectors to develop artificial air flow and to pull smoke out of a structure. Smoke ejectors are placed in windows, doors, or roof vent holes to pull the smoke, heat, and gases from inside the building and eject them to the exterior.

Positive Pressure

When pressure is higher inside a structure than outside the structure, causing smoke and fuel gases to move toward lower-pressure openings.

Positive-Pressure Attack (PPA)

The use and application of high-volume ventilation fans before fire suppression that are intended to force heat and smoke toward desired exhaust openings.

Positive-Pressure Ventilation (PPV)

Method of ventilating a room or structure by mechanically blowing fresh air through an inlet opening into the space in sufficient volume to create a slight positive pressure within and thereby forcing the contaminated atmosphere out the exit opening.

Stack Effect

Phenomenon of a strong air draft moving from ground level to the roof level of a building. The air movement is affected by building height, configuration, and temperature differences between the inside and outside air.

Tactical Ventilation

Planned, systematic, and coordinated removal of heated air, smoke, gases, or other airborne contaminants from a structure, replacing them with cooler and/or fresher air to meet the incident priorities of life safety, incident stabilization, and property conservation.

Trench Cut

Defensive tactic that involves cutting an exit opening in the roof of a burning building, extending from one outside wall to the other, to create an opening at which a spreading fire may be cut off.

Upwind Side

Side of a building against which the wind is blowing, the high pressure side.

Ventilation

Systematic removal of heated air, smoke, gases, or other airborne contaminants from a structure, replacing them with cooler and/or fresher air to reduce damage and facilitate fire fighting operations.

Vertical Ventilation

Ventilating at a point above the fire through existing or created openings and channeling the contaminated atmosphere vertically within the structure and out the top; done with openings in the roof, skylights, roof vents, or roof doors.

How can firefighters control the flow path of fire and smoke during tactical ventilation?

keeping exterior doors closed until a charged line is in place and be positioned at doors that the crew passes through along their path to the fire to close any doors as much as the hose lines in use will allow

What can you do to reduce rapid fire development potential during tactical ventilation?

use appropriate water stream application techniques to cool the heated gases and know-how and when to properly release those gases with appropriate ventilation methods and procedures

How should tactical ventilation be organized with search and rescue crews?

this should be delayed until lines are charged in crews are ready, keeping the fire ventilation-limited longer and prevents fire spread, all rescue teams should be ready to enter the IDLH atmosphere and have a charged hose line available before initiating ventilation, ensuring that everyone's actions are coordinated helps you control amount of oxygen allowed into the structure

What two assumptions should firefighters make about a structure fire to guide their decisions when ventilating a structure?

the structure itself consists of lightweight construction and the fire inside the structure is ventilation-limited

List some of the tactical ventilation size-up factors

Location and extent of the fire, changes to Fire Behavior, spread, and growth, including signs of rapid fire development, affect that ventilation at a location will have on the fire and/or exposures, effectiveness of planned ventilation - desired flow and exhaust efficiency, locations where smoke is escaping the structure (under eve's, vented windows, around doors), type of building construction, building structural integrity, location of overhead power lines, solar panels, and guide wires, locations of two escape locations for roof crews, coordination of fire ground operations with ventilation, and wind direction and strength

How can internal and external exposures affect tactical ventilation?

when ventilation does not release heat and smoke directly above the fire, some routing of the smoke becomes necessary, the roots the smoke and heated fire gases would naturally travel to exit maybe the same routes occupants need for evacuation in firefighters need for working, rising gases might ignite portions of the building above the exhaust point, radiation and/or direct flame contact xan affect expernal exposures

How can firefighters check a roof's integrity for roof ventilation?

Prior knowledge of the roof's construction and the building's layout through incident planning to identify structural elements including lightweight roof trusses, open floor plans under wide expanses with limited trust supports, and prior structural damage to the roof

What specific tools and air movement equipment may be used for tactical ventilation?

Tools include axes, power saws, and pike poles - Air movement equipment includes air movement devices, hose lines and nozzles, flexible ducts, stacking and hanging devices, generators and electrical power cords, wind control device (WCD), and smoke control device

How can firefighters create natural horizontal ventilation?

*door control; these should work with atmospheric conditions, taking advantage of natural airflow, requiring no additional personnel or equipment to set up and maintain

How can firefighters create positive and negative pressure for mechanical ventilation?

Creating negative pressure means artificially lowering the pressure inside the structure so that fresh air from outside moves in more quickly; Creating positive pressure means artificially raising the pressure inside the structure so that smoke and fuel gases move towards lower pressure openings more quickly; this is accomplished using fans, blowers, and smoke ejectors

What are the limitations of horizontal mechanical ventilation?

Depends upon a power source, requires specific equipment, requires more resources and personnel than natural ventilation

What are the advantages of positive-pressure ventilation (PPV)?

Firefighters can set up PPV blowers without entering a smoke-filled environment, it is equally effective with horizontal ventilation or vertical ventilation because it supplements natural air currents just as NPV does, removal of smoke and heat from a structure is more efficient, and exposed buildings or adjacent compartments can be pressurized to reduce fire spread to them

What are the disadvantages of hydraulic ventilation?

the firefighters operating a nozzle must remain in the heated/hazardous atmosphere throughout the operation, the operation can deplete the water supply, particularly during rural firefighting operations where water shuttles are being used, if the operation is performed incorrectly, water damage may be increased within the structure, and more ice will form on the ground surrounding the building when exterior temperatures are below freezing

What safety precautions should you observe when performing vertical ventilation?

Work with the wind at your back or side when cutting a roof opening to protect yourself, ensure that main structural supports do not get cut, guard ventilation opening to prevent personnel from falling, evacuate roof promptly when ventilation work is complete or when ordered to leave, use lifelines, roof ladders, or other means to prevent personal from sliding and falling, make sure roof ladder is firmly secured, exercise caution when working around electrical wires, solar panels, and guide wires, ensured that all personnel on roof are rang full PPE including SCBA and their masks and breathing air, stay out of range of those who are swinging axes and operating power saws, remain aware of overhead obstructions within range, start power tools on the ground to ensure operation but make sure there shut off before hoisting or carrying them to their roof or top of the parapet wall and secure the ladder to the wall or roof, check the roof for structural integrity before stepping onto it and use all available methods to continue monitoring the structural Integrity, before and after ventilating, walk along the load bearing walls and the strongest points of the roof structure whenever possible, when the roof has been opened penetrate the ceiling below to enhance a ventilation

What are the responsibilities of the roof ventilation team leader?

Ensuring the safety of all personnel who are assisting with ventilation operations, ensuring that only the required openings are made, directing efforts to minimize secondary damage - damage caused by the firefighting operations, coordinating the team's efforts with those of firefighters inside the building, ensuring that there are two means of egress from the roof, ensuring the inadequate exhaust opening size, and ensuring that the team leaves the roof as soon as their assignment is completed

Describe the differences between a kerf cut and a triangle cut

The kerf cut is the easiest and fastest inspection hole to cut - making a single cut in the roof surface using a rotary saw, chainsaw, or ax; a triangle cut maybe created from a single curve cut consisting of three overlapping cuts that form a triangle

What are the methods for ventilating a metal roof?

Thin metal roofs - slice open with an ax, carbide tip chainsaw, or rotary saw and peel it back; Thick metal roofs - Metal cutting tools or power saws with metal cutting blades; Industrial buildings with thick roofs - open Skylights, monitors, or scuttle hatches; Sheet metal roofs - Power saws, axes, or large sheet metal cutters

What is the purpose of a trench cut?

to create a defensible line in front of the fire spread

What are the methods for ventilating a basement?

If the basement has ground level windows or below ground level windows in wells - horizontal ventilation can be employed effectively; Natural paths from the basement including stairwells and hoist way shafts can be used to evacuate heat and smoke if there is a way to expel the heat and smoke to the atmosphere without placing other portions of the building in danger ground level door or window and the heat and smoke can be forced from this opening through the exterior openings using fans; Interior vertical ventilation may be required, requiring working on fire weakened floors above the fire (only uses if you are sure the floor will support the weight of necessary personnel and sound the floor to assess the stability before proceeding)

What are the steps for ventilating and controlling stairwells during high-rise fires?

horizontal or vertical ventilation using mechanical means, often times using *horizontal mechanical ventilation devices and the buildings HVAC system; stairwells can be used like a chimney to ventilate smoke, heat, and fire gases from various floors - maintaining control of the doors on uninvolved floors, if applicable - use ventilation fans that are built into stairwells to assist ventilation, *the safest most effective technique is to pressurize the stairwells with PPV fans to confine the smoke to those floors