Smoke and heat extraction

The smoke outlet is an essential element of preventive fire protection and personal protection. In the event of a fire, heat , smoke and hot combustion gases are mostly generated . In contrast to previous approaches, a distinction must be made between smoke and heat extraction . It conducts smoke that arises in the event of a fire from inside a building to the outside.

Manual release unit for a smoke extraction system

If heat extraction is also of interest for reasons of the fire resistance duration of buildings, additional measures must generally be taken for smoke extraction. Due to the combustion process, thermal lifts act. These thermals cause the combustion products (smoke gases) to rise as so-called plume and form a layer of smoke below the ceiling or the roof.

The goals when using smoke extraction systems are diverse. They serve z. B. to keep people on the escape routes smoke-free or smoke-free for a limited time or to enable fire brigades to fire fighting , for which tactical ventilation is used.

Executions

Mechanical and natural systems

A distinction is made between mechanical and natural extraction systems: Mechanical systems remove the combustion products via fans . In natural systems, the products of combustion can safely escape into the open through openings (roof or wall openings) or windows.

What both types of system have in common is that without air flowing in there is no effective discharge of the harmful gases. The post-flow can be realized through openings in the outer walls or fans . Here it is usually necessary to keep the air flowing in with little turbulence (low impulse), i.e. H. with low flow velocities (<1 m / s). In the case of mechanical extraction systems, it is particularly important to ensure that the negative pressure in the room caused by the extraction is not too high and that the door opening forces (on the escape routes) including the action of the door closers do not exceed the limit value of 100N.

A smoke-free area to be protected can generally only be achieved with special smoke protection pressure systems (RDA systems), also in connection with smoke extraction systems.

Smoke extraction and combined smoke and heat extraction

In general, a distinction is made between smoke extraction devices (openings) (RA systems) and smoke and heat extraction systems (RWA). The protection goal and mode of operation must be specified in the building permits with valid fire protection certification or the corresponding special building regulations. Test experts or experts check the conformity of the requirements with the built condition.

SHE systems are listed as safety-related systems that are predominantly subject to testing in accordance with the testing regulations of the federal states in the current building regulations list 2014/1. If a low-smoke layer height is required as a protection goal, this is calculated e.g. B. according to DIN 18232-2: 2007-11 (nat.) Or DIN 18232-5: 2012-5 (mach.) Or must be verified with special engineering methods (smoke simulation).

The SHE systems are to be erected in accordance with the current building regulations list for regulated building products with approved or labeled (CE labeling with DIN EN 12101-1 to -10 evidence) components. Proof of achievement must be presented during the examination. According to Annex 01 of the building regulations list "... the levels, classes and conditions of use specified in the state building regulations and in the regulations based on the state building regulations" apply.

The special flow conditions on the property and in the system technology must be taken into account in the design, dimensioning, zone division and control of the systems.

Triggering the system

The systems can be triggered manually and / or automatically by fire alarms or thermal triggers or by a fire alarm system. It must be possible to trigger the RWA systems manually and, depending on the requirements of the protection goal, can also be done using automatic triggers (smoke or thermal detectors). Manual releases are usually attached to walls in a safe, easily accessible location and require breaking a pane of glass in the event of a fire. As a rule, one control point is required on the ground floor and one on the top landing. Thermal detectors can be designed as glass barrels and are usually assigned to the individual RWA device (NRWG - natural smoke and heat extraction device). Smoke detectors with optical sensors are z. B. mounted at the top in stairwells and trigger the RA system in the event of smoke.

The condition of the system must be clearly identifiable at a central point or at the trigger points for the fire brigade and, if necessary, it must also be able to be changed by the fire brigade (RESET).

Even in the event of a power failure, the RWA / RA system must still remain functional. In the case of electrical systems, this can be achieved through a safety power supply, even directly in the control center. In the case of pressurized gas-operated systems, the system must be supplied fail-safe via pressurized gas cylinders or, in the case of central compressed air systems, as an RWA compressed air boiler or special pressurized gas cylinders (CO ₂ ).

Existing ventilation switches may no longer function during the emergency release (priority switching). It can be permitted to dispense with the secure laying of cables if the system is opened or operated early and safely in the event of a fire using suitable smoke detectors that monitor the entire area of the cable route and this operation can be maintained for the required operating time (if necessary, latching device) . The failure or a malfunction of the system must be reported in good time so that appropriate measures can be initiated before an alarm occurs.

Legal basis

The design and dimensioning of smoke extraction devices in stairwells is determined by the applicable state building regulations, MBO or a special building ordinance (VStättV), currently usually with a geometrical free area of the smoke extraction opening of at least 1.0 m² at the top, depending on the special construction. Special features may need to be observed in the building permits and the applicable fire protection concepts or certificates for fire protection for each property.

standardization

The EN 12101 series of standards (product standard) applies within the framework of European harmonization. Due to the corresponding harmonized product standards, the products must be placed on the market with the CE mark in accordance with the Construction Products Directive . It is not permitted to place these products on the market without a CE mark and declaration of performance.

EN 12101-1: Smoke and heat control - Part 1 Regulations for smoke curtains
EN 12101-2: Smoke and heat control - Part 2: Regulations for natural smoke and heat ventilation devices
EN 12101-3: Smoke and heat control - Part 3: Regulations for mechanical smoke ventilation devices
EN 12101-7: Smoke and heat control - Part 7: Smoke extract ducts
EN 12101-8: Smoke and heat control - Part 8: Smoke control dampers
EN 12101-9: Smoke and heat control - Part 9: Control centers
EN 12101-10: Smoke and heat control - Part 10 Energy supply

The classification of these products from the results of the fire resistance tests (temperature / time) is based on the EN 13501 series of standards.

The planning of smoke and heat extraction systems is based on the application standards (planning principles):

18232-2: Smoke and heat control - Part 2: Natural smoke extraction systems (NRA); Dimensioning and installation
18232-5: Smoke and heat control - Part 5: Mechanical smoke extraction systems (MRA); Dimensioning and installation
18232-7: Keeping smoke and heat free - Part 7: Dimensioning heat exhausts (WA)

history

Orders from Count Palatine Karl IV. From 1772 also served to prevent a fire in connection with domestic fireplaces. According to the simultaneous building regulations, no more wooden chimneys were allowed to be erected, no more wooden hoses were allowed to be installed, which had to lead the smoke from the fireplace to the fireplace , just as it was forbidden to lead stove pipes out of the window.

literature

Frieder Kircher, Rainer Sonntag: Die Roten Hefte, Issue 25 - Preventive Fire Protection . 1st edition. Kohlhammer, Stuttgart 2014, ISBN 978-3-17-016996-8 .

Web links

Smoke and heat extraction systems (RWA) (accessed on March 27, 2020)
Smoke and heat exhaust ventilation devices (accessed March 27, 2020)
Natural smoke evacuation methods - RWA (accessed March 27, 2020)
Mechanical smoke extraction systems (MRA) project planning, construction and maintenance (accessed on March 27, 2020)
RWA today (accessed March 27, 2020)

Individual evidence

^ Franz-Josef Sehr : The fire extinguishing system in Obertiefenbach from earlier times . In: Yearbook for the Limburg-Weilburg district 1994 . The district committee of the district of Limburg-Weilburg, Limburg 1993, p. 151-153 .

[1] Franz-Josef Sehr : The fire extinguishing system in Obertiefenbach from earlier times . In: Yearbook for the Limburg-Weilburg district 1994 . The district committee of the district of Limburg-Weilburg, Limburg 1993, p. 151-153 .