Smoke and heat extraction
Smoke and Heat Exhaust Ventilation Systems (SHEVS) and Natural Smoke Exhaust Ventilation Systems (NRS)
Smoke and heat extraction systems (SHEVS) are an important component of structural fire protection. In the event of a fire, they ensure that smoke and fire gases are removed from the inside of a building to the outside. A distinction is made between natural and mechanical smoke and heat ventilation systems. Natural smoke ventilation systems (NSHEVS) ensure that the products of combustion can escape through ceiling or wall openings. Mechanical smoke extraction systems are installed with special smoke extraction fans or also smoke extraction fans if there is no possibility to fall back on natural systems. The systems are triggered either manually or automatically by fire detectors or fire alarm systems.
Mode of operation of SHEV systems
In addition to the flame, a fire mainly produces smoke, heat and rising fire gases. These rise upwards in the room and form a layer below the ceiling that can lead to complete smoke in the rooms and buildings. The smoke vents ensure a kind of "natural" smoke behaviour so that the fire's own thermals can continue. The existing supply air openings in the lower area provide a kind of chimney effect that creates the necessary balance (smoke extraction).
Tasks of SHEV systems
- Keep escape and rescue routes smoke-free
- Facilitating firefighting
- Delay or prevent the spread of the fire
- Protect goods, facilities and buildings
- Prevent consequential damage due to fire gases
- Faster evacuation of people and animals
- Environmental protection: minimisation of extinguishing agents and thus extinguishing damage
SHEV systems. Electrical, pneumatic and pyrotechnical SHEV systems
Different systems for different requirements are available. With the system components, all types of windows, flaps and skylight domes can be operated automatically and manually, electrically or pneumatically. The decisive consideration when installing a SHEVS is the type of system: systems that can only be opened in case of fire or systems that can also be used for general ventilation.
Independent of any power supply, the pneumatic SHEVS have the advantage of being ready for operation even in the event of a total power failure. These are operated (triggered) via alarm boxes with CO2, or with a so-called thermal triggering device (TAG), which is equipped, for example, with a glass bulb or a fusible link and is triggered independently at approx. 68°C under the dome. The thermal release device is also connected to a CO2 bottle, which ensures that the dome can open independently. Due to the low material usage, the pneumatic SHEVS is the most maintenance-friendly solution.
Electric SHEVS can be triggered either manually with push-button detectors or automatically with smoke detectors. The advantage of the electric SHEV is that it is operated by the emergency batteries even in the event of a power failure. In addition to the protective function in case of fire, this system can also be used for daily ventilation. The system can also be equipped with a wind and rain monitor that automatically closes the ventilation flaps as soon as sudden rain or wind occurs. Retrofitting in existing systems is generally possible.
Also known as pyrotechnic rasant openers, these are smoke vents with explosive gas-operated quick openers. Since there is an extremely high risk of injury or even death if not handled properly, special care must be taken here. Only authorised specialist personnel are permitted to handle pyrotechnic rasant openers. The person carrying out the work should be able to prove that they have received professional training and instruction in pyrotechnic smoke and heat ventilation.