OBJECTIVES
Upon completion of this lesson, you will be able to:
- Define the ventilation.
- Describe the Advantages and disadvantages of ventilation.
- Describe the principle of ventilation.
- Describe ventilation size up.
- Describe the types of ventilation.
Ventilation:
Fire service ventilation is the process of removing smoke, heat, and toxic gases from a burning building and replacing them with cooler, cleaner, more oxygen-rich air.
Advantages of Ventilation:
Proper ventilation assists in:
- To save lives and reduce property damage when ventilation is coordinated with fire attack and water.
- The location and rescue of victims.
- Enables hose teams to advance and locate the source of the fire and prevents fire spread.
- Reduction of flashover and Backdraft potential.
Disadvantages of Improper Ventilation:
- A lack of ventilation or use of improper ventilation techniques can lead to an extension of the fire.
- Injure both firefighters and civilians and increase property damage.
Principle of Ventilation:
When fire is inside a building, the structure acts as a container or box, trapping the products of combustion. As the fire grows and develops, the smoke, heat, and toxic gases spread throughout the structure. The primary principle that controls the spread of smoke, heat, and toxic gases within a room or building is convection.
Ventilation should ideally be done from the highest point of the building. Firemen may create such openings themselves or through doors, windows and other openings by “Forcible Entry.”
Ventilation Size-up:
- Is there a need (Why)?
- Where is it needed (Where)?
- Type needed (How)?
- Structural conditions allow for safe operations.
Coordinated Fire Attack:
Basic Types of Ventilation:
There are Four types of Ventilation:
- Horizontal Fire Ventilation.
- Natural Fire Ventilation.
- Mechanical Fire Ventilation.
- Positive Pressure Ventilation
- Negative Pressure Ventilation
- Hydraulic Ventilation
- Vertical Fire Ventilation.
Horizontal Ventilation
It uses horizontal openings in a structure such as windows and doors and can be employed in many situations, particularly in small fires. Horizontal ventilation is commonly used in residential fires, rooms, and contact fires, and fires that can be controlled quickly by the attack team.
Horizontal ventilation is more difficult if there are no direct openings to outside or if the openings are in accessible. Fire fighters may need to use horizontal ventilation if an inaccessible or damaged roof makes vertical ventilation impossible. Horizontal ventilation tactics include both natural and mechanical methods.
Natural Ventilation
Natural ventilation depends on convection currents, wind, and other natural air movements to allow a contaminated atmosphere to flow out of a structure. Opening from a window or door will allow these products of combustion to escape through natural ventilation. Natural ventilation is offend used when quick ventilation is needed such as when attacking to first-floor residential fire with people trapped on the second floor.
Wind speed and direction play an important role in natural ventilation. Openings on the windward side can be used for cross ventilation, bringing in clean air. Conversely, opening a window on the windward side first could push the fire into uninvolved areas of the structure, particularly on a windy day.
Mechanical Ventilation
Mechanical ventilation uses mechanical means i.e. use of fans or other powered equipment. There are three different methods of mechanical ventilations. Negative-pressure ventilation uses fans called smoke ejectors to exhaust smoke and heat from a structure. Positive-pressure ventilation uses fans to introduce clean air into a structure and push the contaminated atmosphere out. Hydraulic Ventilation moves air by using fog or broken pattern fire streams to create a pressure differential behind and in front of the nozzle.
Negative Pressure Ventilation
The basic principles of air flow are used in negative pressure ventilations. Using a fan or bluer, exhaust the products of combustion out through a window or door. The fan draws the heat, smoke and fire gasses out by creating a slightly negative pressure, where it replaces the contaminated air. Smoke ejectors are usually 16 to 24 inches diameter, although larger models are available. Negative pressure ventilation has some limitations related to its positioning, power source, and maintenance and airflow control.
Positive Pressure Ventilation
Positive pressure ventilation uses large, powerful fans to create a positive pressure inside the structure, which displace the contaminated atmosphere and pushes heat and other products of combustion out. Positive pressure fans are usually setup at exterior doorways, often at the same opening used by the attack team. Positive pressure ventilation will not work properly if there are too many openings, although there must be an opening near the seat of the fire to allow the heat and smoke to escape. If the fire is located in structural void spaces, positive-pressure ventilation should not also be used without an adequate exhaust opening for the heat and smoke.
Hydraulic Ventilation
Hydraulic ventilation uses the water stream from the hose line to exhaust smoke and heated gasses from a structure. To use this ventilation technique, the fire fighter working the hose line directs a narrow fog stream from nozzle out of the building through an opening, such a window or door ways. An induced draft created by the high-pressure stream of water pulls out the smoke through the opening. A well-placed fog stream can move a great volume of air through an opening.
Hydraulic ventilation is most useful in cleaning smoke and heat out of a room after a fire is under control. To perform hydraulic ventilation, the firefighters enter the room and remains close to ventilation opening. The operator places the nozzle through the opening and opens the nozzle to a narrow fog or broken spray pattern. The operator keeps directing the stream outside and backs into the room until the fog pattern almost fills the opening. The nozzle should be 2 to 4 feet inside the opening. This technique can cause excessive water damage if it is used improperly or for long periods of time.
Vertical Ventilation
Vertical ventilation refers to release of smoke, heat and other products of combustion into the atmosphere through vertical openings i.e. sky lights or which created by the fire fighters at roof covering in a vertical direction. A vertical ventilation opening should be made as close as possible to the seat of the fire. Convection causes the products of combustion to rise and flow through the opening. In some situations, vertical ventilation can be assisted by mechanical means such as fans or hose streams.
Conclusion
In conclusion, ventilation is a crucial element in firefighting operations, playing a vital role in controlling fire spread, protecting lives, and minimizing property damage. Understanding the different types of ventilation—horizontal, vertical, natural, mechanical, positive pressure, negative pressure, and hydraulic—is essential for ensuring effective fire suppression and rescue efforts.
Properly executed ventilation allows for better visibility, reduced heat, and improved oxygen levels, enabling firefighters to locate and extinguish the fire more efficiently. However, improper ventilation techniques can lead to fire extension, increased risk of injury, and greater property loss.
By following the principles of ventilation and conducting a proper ventilation size-up, firefighters can make informed decisions to ensure safe and effective fire control. Mastery of these ventilation techniques not only enhances firefighter safety but also significantly increases the chances of a successful rescue and fire attack. Adopting the right ventilation strategy at the right time can make a critical difference in the outcome of any fire emergency.
Emma Lee, an expert in fire safety with years of firefighting and Rescuer experience, writes to educate on arescuer.com, sharing life-saving tips and insights.