Under the German state building codes, necessary stairwells must be ventilated and capable of being cleared of smoke in the event of fire. This is usually done via openable windows on each floor or via a smoke vent at the top with a free cross-section of at least 1 m\u00b2. This guide explains the requirements, the operation and what a window actuator has to achieve.<\/p>\n\n\n\n
In brief:<\/strong> Under the state building codes, stairwells on escape routes need smoke venting: openable windows on every floor or an opening at the highest point with at least 1 m\u00b2 free area. The opening must be operable from the ground floor and from the top landing. The details depend on the federal state and the building class.<\/p>\n\n\n Note: the requirements differ by federal state and building class. This guide does not replace planning by a fire protection planner or coordination with the building authority.<\/em><\/p>\n\n\n The rules are set out in \u00a7 35 of the respective state building code, for example \u00a7 35 BauO NRW<\/a> or \u00a7 35 of the Hamburg building code. In essence, both state:<\/p>\n\n\n The Hamburg building authority has published an FAQ on \u00a7 35 HBauO<\/a> on this (as of 10 June 2026). According to it, in buildings of building classes 4 and 5 without openable windows in the stairwell, a natural smoke and heat exhaust ventilator (NSHEV) with at least 1 m\u00b2 free opening area at the top must be provided, plus an air inlet on the entrance floor that is at least as large. For large or angled stairwells with more than 40 m\u00b2 floor area, the FAQ gives an opening of 5% of the floor area as a guide.<\/p>\n\n\n What is required is the free cross-section<\/strong>, i.e. the area through which smoke can actually escape. With a top-hung or bottom-hung sash it is considerably smaller than the glass area, because the sash only opens to a certain angle. A window with 1 m\u00b2 of glass therefore usually does not reach 1 m\u00b2 of free cross-section. Sash size, opening angle and thus the Stroke<\/a> of the actuator are decisive. Have the free cross-section verified by the window manufacturer or planner.<\/p>\n\n\n The opening at the top should open in the event of fire so that smoke and heat escape upwards and the fire brigade can use the stairwell better. Its main purpose is to support firefighting. For smoke to escape, air must also come in from below, for example through the entrance door or a dedicated air inlet. Which windows open or stay closed is defined in the fire protection concept.<\/p>\n\n\n That depends on the requirement. Where an NSHEV is required, the unit of window and actuator must be tested as a whole according to EN 12101-2. Any window with a retrofitted motor is then not an NSHEV. Where only a smoke vent with 1 m\u00b2 free cross-section is required, a motorised window with SHEV control may be an option if the free cross-section is verified. The difference is explained in the guide SHEV and NSHEV<\/a>.<\/p>\n\n\n Vent Systems supplies chain, spindle and rack-and-pinion actuators for ventilation and SHEV. SHEV control panels are not part of our range. For inspection and maintenance, see RWA maintenance and inspection obligations<\/a>.<\/p>\n\n\n Which standards apply to smoke ventilation and what they mean for window actuators is explained in our overview Smoke ventilation standards: DIN EN 12101-2, DIN 18232 and building codes<\/a>.<\/p>\n\n\n\n Every necessary stairwell must be capable of being ventilated and cleared of smoke. In many buildings, openable windows on each floor are sufficient. In buildings of building class 5, an opening at the top is always required. Which solution applies to your building should be clarified with your planner or the building authority.<\/p>\n\n\n Yes, with a SHEV control panel with ventilation function. The fire case always has priority, see SHEV and daily ventilation<\/a>.<\/p>\n\n\n Planning, installation and inspection belong in the hands of specialist companies for smoke and heat exhaust. The electrical connection is carried out by a qualified electrician.<\/p>\n\n\nWhat the building code requires<\/h2>\n\n\n
Free cross-section is not the window size<\/h2>\n\n\n
How is the opening operated?<\/h2>\n\n\n
Open or close in the event of fire?<\/h2>\n\n\n
Is a normal roof window with a motor enough?<\/h2>\n\n\n
What the actuator has to achieve<\/h2>\n\n\n
Frequently asked questions<\/h2>\n\n\n
Do I need a smoke vent in the stairwell of every apartment building?<\/h3>\n\n\n
Can the smoke vent also be used for ventilation?<\/h3>\n\n\n
Who may install and inspect the system?<\/h3>\n\n\n
Actuators for your project<\/h2>\n\n\n