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Posted by on Jul 10, 2017 in Firefighting methods |

Why Do Firefighters Break Windows and Cut Holes in Roofs?

As a fire burns, it usually moves upwards, then outwards. Breaking windows and cutting holes in the rooftop, or “ventilation” in firefighting jargon, stops that destructive outward movement and allows firefighters to fight more efficiently, causing less damage in total. It also reduces the amount of hydrogen cyanide and carbon monoxide from building up inside the building, which reduces the chances of smoke explosion (Backdraft) and it buys potential victims more time.


Ventilation is a crucial process of almost any firefighting operation. The ability to eliminate fire gasses, heat and smoke from a burning building can really help with the ability to locate victims. It creates a more survivable situation for the victims, eases the environmental impact firefighters have to work in and accelerates the ability to for firefighters to put out the fire.

Proper ventilation delivered at the wrong time and improper ventilation can greatly increase the amount of work required to complete fire ground tasks by spreading fire and increasing heat and it could ultimately contribute to the injury or death of firefighters. Ventilation methods used by the fire service include hydraulic ventilation, vertical ventilation, and mechanical ventilation. All of these processes allow for the removal of hazardous fire products and replacement of these with fresh air.

When Should Firefighters Begin Ventilation?

Ventilation should be considered before fire crews start operating inside a structure. Fire build up should be on every firefighter’s mind. Ventilation is often an afterthought, only brought up when an interior crew is driven to the ground from high heat and low visibility.

When dealing with heat, smoke, and fire gasses, science plays a vital role. In the most basic form, all elements of the fire triangle create pressure and these forces are doing everything they can to balance pressure by escaping out the path of least resistance. So when firefighters run into a burning building without addressing ventilation, they have typically made their point of entry the path that the fire will take.

Natural Ventilation

This method of ventilation isn’t regarded as a mechanical ventilation procedure; it doesn’t require anything to direct the flow of air out of or into a building. Remember that taking out doors and windows is a safe way to allow hazardous fire products to exit the building, but this needs to be coordinated with interior crews.

Additionally, if positive pressure is the method your crews may be using in the future, are you removing your ability to regulate the interior air flow? This process must still be considered with incident command to ensure only the windows necessary are being removed; unnecessarily breaking windows that aren’t necessary to extinguish the fire is poor customer service and puts firefighters at risk.

Mechanical Ventilation

If used appropriately, mechanical ventilation can assist with and make ventilation more effective. Once the fire source is extinguished, the interior crew can use the water stream to ventilate the zone. This method is referred to as power venting or hydraulic ventilation. It’s achieved by directing the hose stream out a window opening from the structure. The line is repositioned further away from the window opening, and a thin fog pattern is used to shield as much of the opening as possible to create a lower pressure at the window as that within the building. The smoke, heat, and gasses will be drawn past the stream following the path of least resistance and be drawn out of the area through the window.

Vertical Ventilation

Most fire fighters are aware of the science of fighting fires, thanks to training from webcasts, written articles, and online and offline classes. After such studies, many fire service members prefer not to ventilate roofs, mainly due to lightweight building construction techniques. But vertical ventilation can be safe and effective based on experience, research, and knowledge. However, vertical ventilation cannot be implemented at will without collaborating with the attack crew.

Horizontal Ventilation

Horizontal ventilation allows air flow to discharge dangerous smoke, heat, and gases. It is the process of creating an opening on the fire floor to allow smoke, heat, and gases to travel horizontally out of the building without altering or reducing the effect, to the unaffected areas of the structure.

Positive Pressure Ventilation

This is one of the basic methods used by the fire service. When used appropriately, it’s a great problem solver. The process essentially uses ventilators to force air into a structure, releasing smoke and heat in a quick, controlled manner. Positive-pressure ventilation will work effectively in all areas but will need assistance in high rises if it’s being used as the only means of ventilation.

Effects of Proper Ventilation

Effective ventilation dramatically assists in the control, attack, and extinguishment of a structure fire. Let’s have a look at some of the effects of proper ventilation in firefighting:

  • Reduced temperature levels

  • Reduced smoke damage to property

  • Reduced temperature levels.

  • Controlled impurities level

  • Better visibility

  • Reduced possibility of flashover/backdraft

  • Easier to locate source of fire or victims


Ventilation is a very important tactic that can have as great an impact on fire behavior as the application of water. The problem is that the window of time to be effective can be very small, so it’s very important to apply appropriate ventilation techniques at the right time.