Escape Routes and Fire Stairs: The Design Logic

Under Article 4(ü) of the Turkish fire regulation (BYKHY), an escape route is the whole unobstructed path from any point of a building to the street at ground level, including exits from rooms and other separate spaces, corridors and similar passages on each floor, storey exits, stairs leading to the ground floor and routes to the final exit. Two words summarise the design: continuous and protected.

Three parts

The NFPA 101 approach of treating the escape route in three parts maps onto the components listed in BYKHY Article 31(1) (room exits, corridors, storey exits, stairs down to the ground floor, routes on the ground floor to the final exit, and the final exit itself):

1. Access to escape. From the room to the corridor and on to the stair door. This part is closest to the room of fire origin and the least protected.
2. Protected escape. The stair enclosure or protected corridor. This part must stay clear of smoke and heat; escape stairs are separated by walls with at least 120 minutes of fire resistance and smoke-tight doors with at least 90 minutes (Article 38(3)).
3. Final exit. From the stair discharge to a place of safety outside the building. Obstruction, locked doors and parked vehicles are the usual problems here.

Core principles

• Two-way escape. Occupants must be able to turn the other way when one direction is blocked by fire. BYKHY requires at least 2 exits in every building unless stated otherwise (Article 39(1)); at least 2 exits in high-hazard spaces with more than 25 people and in any space with more than 50 people, at least 3 above 500 people and at least 4 above 1,000 people (Article 39(2)). A single exit is accepted only in limited cases, for example a ground-floor shop with fewer than 50 people and a travel distance of less than 25 m (Article 32(8)).
• Travel distance. The walking distance from the most remote point of a space to the nearest exit may not exceed the Annex 5/B values for the occupancy class, with and without sprinklers (Articles 32(3) and 32(4)). The most remote point is taken 40 cm in front of the enclosing walls (Article 32(6)).
• Exit capacity. The capacity of doors, stairs and corridors is calculated in 50 cm units of width; the number of people per unit width is given in Annex 5/B (Article 32(2)). The total exit width may not be less than the Article 33(1) formula, and no escape route may be narrower than 80 cm. The calculation covers the whole chain, not a single door; the narrowest point sets the capacity.
• Door swing and hardware. In spaces with an occupant load above 50, exit doors open in the direction of escape, and escape doors may not be kept locked (Article 47(2)). All escape doors leading from a stair to a safe area at ground level, and, where more than 100 people are on a floor, also escape stair, escape corridor and fire lobby doors, must open in the escape direction without using a door handle (Article 47(5)); in practice this is panic hardware.
• Dead ends. The length of dead-end corridors, where occupants cannot choose between two directions, is limited: under Annex 5/B, 15 m without sprinklers and 20 m with sprinklers for most occupancy classes (10 m and 20 m in high-hazard premises).

Protected stairs and pressurisation

Every protected escape stair must be naturally ventilated, or mechanically ventilated or pressurised (Article 45(1)). Pressurisation is mandatory in non-residential buildings where the stair shaft is more than 30.50 m high, in stairs serving the basement where there are more than 4 basement levels, and in residential buildings with a total structure height above 51.50 m (Articles 89(1) to 89(3)). A pressurisation design must satisfy two conflicting requirements at once:

• With all doors closed, the pressure difference between the stair enclosure and the occupied areas must be at least 50 Pa, and at least 15 Pa with a door open (Article 89(5)).
• The force needed at the door handle to open the door, against both the pressurised air and the door closer, may not exceed 110 N (Article 89(7)).

Both are only achieved together with an overpressure relief damper or a variable-speed fan (Article 89(11)) and correct fan control. At commissioning both the pressure difference and the door opening force are measured; checking only one is a common omission.

Emergency lighting and signage

The escape route must stay visible when power fails. Points to watch:

1. All escape routes and escape stairs are lit (Article 71(1)). Emergency lighting provides at least 1 lux on the centre line of the escape route and may not fall below 0.5 lux at any point by the end of its rated duration (Article 72(4)). Lighting is concentrated at changes of direction, stair heads, level changes and exit doors.
2. Signage must form an unbroken chain and be visible from every access point along the escape route (Article 73(7)).
3. Exit signs are mounted between 200 cm and 240 cm above the floor (Article 73(5)); the sign height may not be less than 15 cm (Article 73(4)).
4. Emergency lighting and signage must run for at least 60 minutes, or at least 120 minutes where the occupant load exceeds 200 (Articles 72(3) and 73(3)). Battery duration and periodic functional testing are recorded.

The eight most common breaches on site

• Stair landings used for storage (Article 38(4)).
• Fire doors wedged open.
• Exit doors locked for security reasons (Articles 30(4) and 47(2)).
• Vehicles parked in front of the final exit.
• Corridor width narrowed with cupboards and boards.
• Signage removed during refurbishment and never refitted.
• Emergency luminaires with batteries past their life.
• Service shaft access panels opening into the stair enclosure, or meters and combi boilers installed in it (Article 41(9)).

What those eight have in common is that they are operational, not design, failures. Fire safety management is therefore the complement to the design, not an alternative to it.

Frequently Asked Questions

Why must an escape route be continuous and protected?

BYKHY Article 4(ü) defines the escape route as the whole unobstructed path from any point of the building to the street, and Article 39(1) requires exits to be protected. Unprotected elements such as open stairs that do not pass more than one storey can be accepted under the conditions of Article 31(7), but on floors with more than 50 occupants at least half of the escape routes, by capacity and by number, must be protected.

How is exit capacity calculated?

The capacity of doors, stairs and corridors is calculated in 50 cm units of width, with the number of people per unit given in Annex 5/B (Article 32(2)). The total exit width may not be less than the floor occupant load divided by the people per unit width, multiplied by 0.5 m (Article 33(1)). The calculation covers the whole chain; the narrowest point sets the capacity.

Which two measurements are taken on a pressurisation system?

The pressure difference with doors closed (at least 50 Pa, and at least 15 Pa with a door open; Article 89(5)) and the door opening force (no more than 110 N; Article 89(7)). Checking only one is a common omission.

Do sprinklers change travel distance?

Yes. The maximum travel distances in Annex 5/B are longer in sprinklered buildings; for offices, 30 m instead of 15 m one way and 75 m instead of 45 m two ways. Core principles such as a minimum of two exits and protected escape stairs remain.

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