A Quick Guide to Smoke Ventilation Systems

For all new build projects as well as existing buildings, there are many regulations and rules surrounding the installation of smoke vents and systems for ensuring a safe environment in the case of fire. These systems are known as Smoke and Heat Exhaust Ventilation (SHEV) systems and have a key role in saving the lives of a building’s occupants.

Statistics show that 90 percent of fire related fatalities are caused by smoke poisoning from fires within buildings. The importance of smoke vents and SHEV systems, therefore, cannot be underestimated.

The principal aim of SHEV systems is to lead smoke and heat out of burning buildings, all whilst keeping escape corridors and stairs free of smoke. This is important for the evacuation of occupants of the building, allowing them to exit whilst avoiding the toxic smoke fumes coming from the fire.

The SHEV system and smoke vents also allow for fire fighters and first responders to enter the area, meaning that passages are sufficiently clear for them to attend to occupants in need as well as reach the source of the fire in order to extinguish it.

In addition to this, a SHEV system is helpful in avoiding dangerous fire heating, which is the main cause of flashover where building fires rapidly accelerate. All these factors highlight just how essential SHEV systems are in buildings in preventing loss of life and massive destruction of property.

Different types of building have different needs when it comes to installing SHEV systems, and only fully trained experts should be tasked with designing and installing a smoke vents system that meets and exceeds safety requirements.

Both natural and mechanical ventilation systems can be used as part of SHEV systems, with each one suited to a different type of building. Natural smoke ventilation relies on the buoyancy of hot gases, and uses automatically-opened vents to draw rising smoke, heat and dangerous gases off out into the open naturally.

For a smoke vent system such as this to work optimally, it is necessary to have replacement or ‘make up’ air to provide fresh air openings in the lower part of the building to achieve the effect of a rising thermal current and draw smoke, fumes and heat out of the building. This can be achieved by using Automatic Opening Vents (AOV) and doors.

Upon detection of smoke, these AOVs will open automatically via electric actuators (motors) or magnetic locks. Firefighters are given the ability to override this system at various manual call points placed throughout the building. A system such as this will be linked to a central control panel as well as a battery backup, ensuring that the SHEV will work even if the mains supply fails.

The timing of the opening of smoke vents is of critical importance, as it is this which allows occupants to escape quickly. It is therefore recommended by many professionals that an automatic vent system as described above is put into place for maximum efficiency and safety.

There are several different possible locations for automatic opening smoke vents, including: the automatic opening window, which releases smoke into the atmosphere; the smoke shaft and AOV, where smoke flows via a window or door to the vent and then out into the atmosphere; and the stairwell AOV, where smoke flows though an AOV at the top of a stairwell.

Mechanical ventilation systems are generally used where natural ventilation is limited due to architecture. This can occur in higher buildings where smoke buoyancy and up-venting are insufficient. In these cases, smoke shafts are placed adjacent to common areas such as stairs, lobbies and corridors to extract smoke and heat.

Even in the absence of a natural smoke vent system, this allows for improved safety conditions allowing occupants to evacuate the building and firefighters and first responders to access the scene and carry out their work quickly and efficiently.

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