Tactical Ventilation

Explore Tactical Ventilation strategies, including vertical, horizontal, and forced methods, to enhance safety and control fire spread.

Basics of Ventilation

Ventilation is a crucial tactic in firefighting operations. There are two main types of ventilation used during a fire: horizontal and vertical. Horizontal ventilation can be further divided into two categories: life-saving ventilation and fire control ventilation.

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In residential firefighting, proper ventilation is vital. When done correctly, it creates safer conditions for firefighters, increases the survival time for trapped victims, and supports all firefighting operations on the scene.

There are two main types of ventilation techniques used during firefighting: vertical ventilation and horizontal (or lateral) ventilation. Using both techniques together allows for safer and more effective operations.

Vertical Ventilation

Vertical ventilation is a tactic used in the early stages of firefighting operations in the United States for various reasons. When done properly, it removes heat, smoke, and gases from the top of the building, preventing what’s known as a “smoke mushroom.” A smoke mushroom occurs when heat and smoke spread horizontally and are pushed down into the lower parts of a structure, aiding fire spread.

Most importantly, vertical ventilation can increase the survival time of victims trapped or unconscious above the fire area. Searching for victims above the fire area can be more effective, as firefighters face fewer hazards during the search.

Vertical ventilation also helps clear stairwells of heat and smoke, allowing firefighters to advance hose lines more quickly. However, it’s crucial to coordinate the timing of ventilation with hose line advancement, as premature ventilation can cause the fire to spread. Vertical ventilation involves creating openings in the roof, such as breaking skylights or cutting through the roof as needed.

Horizontal Ventilation

Horizontal or lateral ventilation involves opening and closing windows in the building. Firefighters can also create openings intentionally. This technique allows for the rapid advancement of hose lines into the fire area, reducing the risk of heat or fire spreading over or around the firefighting team by venting heat and smoke through the newly created openings. It also facilitates thorough search procedures on both the fire floor and upper floors. It’s important to ensure that charged hose lines are in place before initiating horizontal ventilation, as fire can spread rapidly through these openings if not properly controlled.

Life-Saving Ventilation

Life-saving ventilation is done to allow firefighters to access victims at risk inside the building. This type of ventilation is dangerous because it can cause the fire to spread. As mentioned earlier, ventilation carries certain risks, and firefighters must always consider these potential hazards, especially when they are the incident commander. It’s essential to weigh the risks and benefits carefully.

When entering through a window that has been ventilated for search purposes, make sure to completely clear the window opening. Remove any bars, window sashes, curtains, shades, air conditioners, or other objects that might obstruct the opening. Ensure that the opening is fully clear to allow for easy removal of victims or to provide an escape route if needed. After clearing the area around the window, close the door before starting the search. Closing the door helps increase search time and reduce risks.

It’s crucial to coordinate horizontal ventilation between the ventilation team and interior firefighting personnel. Uncoordinated or poorly timed horizontal ventilation can cause the fire to spread rapidly, endangering personnel inside and hindering operations.

The Importance of Proper Ventilation

When executed correctly, proper ventilation techniques significantly contribute to the success of firefighting operations. Although not all aspects of ventilation can be controlled, proper techniques enable safer actions and can extend the survival time of both firefighters and victims. There is no substitute for a well-coordinated firefighting operation, and ventilation is a vital component.

The primary objective of tactical ventilation is to improve the internal environment for victims and firefighters by intentionally managing the flow path. Openings are created horizontally or vertically, as shown in the diagram, to generate flow paths using differences in the pressure and density of heated gases or mechanical and hydraulic forces.

When using ventilation tactics along with interior firefighting, firefighters must continuously control the environment using hose stream techniques to cool and dilute highly combustible smoke.

The Effects of Ventilation

The National Institute of Standards and Technology (NIST) in the U.S. has scientifically demonstrated that the mass of hot gases exiting from a fire must be replaced by the same mass of fresh air. This fresh air can increase the heat release rate, potentially leading to Flashover and Growth Incidents (FGI). If ventilation is used incorrectly or at the wrong time, it can increase safety risks. Below are the effects of ventilation:

Effects of Ventilation:

Smoke and heat are drawn toward the exhaust opening.
Reduces the accumulation of hot smoke.
Increases heat release rate (risk of rapid fire spread).
Adds fresh oxygen (risk of rapid fire spread).

Natural Ventilation

Natural ventilation involves replacing the polluted air inside a building with fresh outside air, based on the pressure differences between the interior and exterior of the building and the surrounding wind conditions. Here are the pros and cons of natural ventilation:

Natural Ventilation:

Pros	Cons
Can use existing openings	Relies on natural airflow
Utilizes natural airflow	Airflow might enter clean areas of the building
Leverages the physical properties of smoke (buoyancy and expansion create pressure differences)	Ventilation paths might be evacuation routes
Removes smoke and heat	Can increase fire spread
Ideal for “hot” smoke	Limited effectiveness on “cold” smoke
Dependent on wind conditions

Forced Ventilation

Forced ventilation involves creating a pressure difference using blowers to replace the polluted air inside a building with fresh outside air. Here are the pros and cons of forced ventilation:

Forced Ventilation:

Pros	Cons
Speeds up the removal of smoke and heat	Can rapidly increase fire spread
Can overcome natural wind effects (to some extent)	Might rapidly spread fire into voids
Can be used to move both “hot” and “cold” smoke	Can create destructive overpressure, leading to ignition

Water-Powered Ventilation

Water-powered ventilation involves using a fog pattern or straight stream in an “O” pattern directed from inside toward an opening to create a pressure difference, replacing the polluted air inside a building with fresh outside air. Here are the pros and cons of water-powered ventilation:

Water-Powered Ventilation:

Pros	Cons
Speeds up the removal of smoke and heat	Requires water
Can overcome natural wind effects (to some extent)	Usually not used in initial firefighting due to the need for a nozzle
Can be used to move both “hot” and “cold” smoke	Improper use can cause water damage
Can be used with hose lines only	Nozzle operator must remain in heated/polluted areas
Most useful after fire suppression

Effects of Height Differences in Openings

When using these ventilation methods, the greater the height difference between the inlet and outlet, the greater the airflow of both air and smoke. Considering the buoyancy of hot smoke, creating an exhaust opening above the inlet can enhance the effectiveness of both horizontal and vertical ventilation.

Smoke, composed mainly of carbon particles, is solid. Solid carbon is heavier than air, so it cannot rise on its own. However, near a fire, the air heats up and becomes lighter than the surrounding cooler air, causing it to rise. This is known as an updraft, which can carry small carbon particles upward.

It’s important to remember that an increase in inward airflow can lead to an increase in the heat release rate.

Controlled Ventilation (Non-Ventilation)

Controlled ventilation involves intentionally containing heat, smoke, or airflow. Flow path management is achieved by blocking air inlets or controlling heat and smoke outlets. Ventilation points, such as doors, are closed.

Controlled ventilation can have a suffocating effect on the fire, preventing smoke, heat, and flames from moving into another area.

Tactical Non-Ventilation:

Pros	Cons
Delays fire spread	Cannot remove combustion products (e.g., CO) from the fire room
Not affected by surrounding wind conditions	Poor internal visibility
Keeps smoke, heat, and flames away from unaffected areas	May worsen conditions for interior firefighting teams

Reference page: “Key fire characteristics: combustion elements, smoke risks, toxic gases, and safe firefighting techniques.”

References　National Fire Protection Association (NFPA)

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Tactical Ventilation