In every fire without exception, the uncontrolled burning of materials causes very large quantities of smoke and toxic gases to be produced. These "waste products" of a damaging fire have many negative effects. Affected building parts quickly fill with smoke hampering some fundamental protection goals of fire protection considerably.
Active and passive rescue and evacuation of people as well as effective extinguishing work are massively impaired. Therefore, it must be a priority to remove the smoke as effectively and as fast as possible from the buildings or to limit it at least to a manageable range. The only way to remove fire smoke from buildings is either to extract it mechanically, i. e. with fans, or, which is much easier, to discharge it into the open air via existing building openings.
This "natural" smoke extraction is supported by the fact that the corresponding building openings are already present in the form of windows and doors and that the buoyancy effect can be used at the same time. The hot gases rise and develop a high flow dynamic that can be used.
Electric actuators are used worldwide to open the windows, flaps and roof windows used for this purpose. These opener units are usually designed in 24 Volt DC, as this also ensures a simple and cost-effective emergency power supply in the event of a fire. If such a smoke extraction system is implemented, one of the most important questions is the required opening area. Natural smoke extraction only works if sufficient areas are created in the building envelope for the fire gases escaping into the air. European experts draw a clear and sensible line at this point. Germany, for example, has even clearly decided to establish this limit in building law. With a fire compartment area of up to 1.600m², the ventilation area is always calculated as a percentage of the base area. 1% of the base area if the smoke is vented through the roof and 2% if from the facade.
It is also important that no further requirements are placed on these openings apart from the geometrically effective area. Existing windows in the upper third of the facade (see Fig. 4 ④) and roof windows, or skylight domes which are opened in case of fire meet these requirements when the aggregate free area requirement is achieved. The triggering of such a system is automatically ensured by smoke detectors (see Fig. 4 ⑦). There are also explicit legal regulations regarding the smoke extraction of stairwells. Because these are the primary escape route and require a separate consideration! Also here the legislator specifies the ventilation area as a percentage of the floor area. The requirement is defined as follows -5% of the floor area but at least 1m².
Components used in automated smoke extract openings usually fulfil the requirements of DIN 18232-8. Reliability and heat resistance are the main requirements. It is a widespread misconception that these smoke extraction openings must meet the requirements of an NSHEV according to DIN EN 12101-2. This harmonized European standard defines exclusively the requirements for a construction product and not the regulations for its use.
The determination of the necessary use of such NSHEV's is a task of the legislator.
Only where, for example, the surface area of the section to be ventilated is larger than 1.600m², does building law in Germany require it's use. This regulation makes perfect sense for several reasons and is also intended by the legislator. Testing an NSHEV is complex and the results limit its use to the combination of smoke extraction opening and opener unit. Thus, there is no possibility to freely select window profiles and combine them with suitable units.
In addition, the product standard EN 12101-2 clearly regulates the area of application. The NSHEVs are designed to create a smoke-free layer in a section of a building that is considered to be one storey. In Germany, the height of this low smoke layer is specified in DIN 18232-2 at a minimum of 2.5m (see Fig. 2) above the floor. It is clear that this requirement cannot be achieved in a residential lobby or stairwell where there is insufficient height and indeed no system design has been undertaken to arrive at the free area. Unfortunately, this requirement is sometimes discussed - an NSHEV in a staircase or lobby as a smoke extraction opening. But one thing is clear: an NSHEV is neither intended for the staircase or lobby nor can it form the low smoke layer provided for in the standard. Existing facade or roof openings in the building envelope to be used as smoke extraction openings are absolutely legally compliant.
Simon Protec offers both solutions! Tested opener units which have at least one proof of durability and heat resistance and are suitable for use in residential stairwells and lobbies.