Natural Vs Mechanical Smoke Ventilation

Smoke ventilation systems keep the escape routes such as corridors and staircases of residential buildings clear by quickly removing smoke. This ensures that residents or workers can escape safely and that fire fighters have good access to a building.

There are two different types of ventilation systems available, mechanical and natural, but what’s the difference and which one is best for your building?

How to choose between natural and mechanical smoke venting

Quite often, what system you choose will depend on the way in which your building is designed. The British Standards requirements vary depending on the height of your building, as well as the distance from the furthest apartment door to the nearest escape route and determines what type of smoke ventilation you’re building will need.

The British Standards state that in residential buildings that are four or more storeys in height (or a floor over 11m from the access level) must have a maximum travel distance of 7.5m. To achieve code compliance a 1.5m² automatic opening vent (AOV) window or a natural smoke shaft of 1.5m² must be provided. This is to ensure that all residents or staff members have a protected escape route.

If a property’s common corridor has an external wall, you might find that a natural smoke ventilation system is the most cost effective option as the existing windows of the building can be used for ventilation purposes. Another benefit of natural venting systems is that they require very little maintenance compared to mechanical systems. This is due to their limited number of mechanical parts generally just consist of an actuator and fire doors. The natural option is perfect for buildings on a restricted budget or those worried about issues with vandalism.

Advantages of mechanical smoke ventilation

Whilst natural smoke ventilation may be cheaper, there are many advantages to a mechanical smoke ventilation system. The British Standard (BS 9991: 2011) states that mechanical ventilation systems must be as effective if not more so, than their 1.5m² natural counterparts. However, due to the enhanced efficiency of mechanical systems, shafts as small as 0.25m² to 0.5m² can be used although typically these are 0.5m² or 0.6m², providing building owners more saleable space.

Like natural systems, mechanical smoke venting systems must keep common corridors and staircases free from smoke. However, due to the increased efficiency of some mechanical systems, they may be used in buildings that contain travel distances in the common corridor that extend past the code recommended 7.5m as they provide enhanced performance for means of escape. Although mechanical systems can be more expensive initially due to equipment and set up, these costs are offset by the amount of extra saleable space available to you and design benefits once this system has been fitted.

Which Type to Choose?

Both natural and mechanical smoke venting systems offer advantages to residential developments. What type you choose will ultimately come down to building type, your buildings design and of course, your budget. These factors show why it is so important to work alongside experienced fire engineers when planning the initial design of your building. By working closely with fire design experts, you can create a bespoke fire safety system that works in harmony with the rest of your building.

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