Homes and gardens

Basic exit requirements in high-rises, public buildings

exit  

There is a need for the public and occupants to to know the details of exits in any building from the fire safety point of view. This need primarily can be taken care of by the architect who prepares the plans and the fire services who check the same for compliance. The National Building Code (NBC) specifies the requirements of exits for different occupancies.

The NBC (b) specifies the following occupancies: Residential; Educational; Institutional; Assembly; Business; Mercantile; Industrial; Storage; Hazardous.

Examples of occupancies are also given.

Panic in the event of fire is normal. But this can be avoided if the occupant can clearly see the signs of exit and its direction with no obstruction in the path of travel.

Means of access

The width of means of access shall be 6 m for residential occupancy and not less than 12 m for other occupancies depending on the length of the means of access. In addition, the road shall not terminate in a dead-end and shall join another street of 12 m width. The compulsory open spaces shall not be used for parking.. Adequate passage way for fire-fighting vehicles shall be provided at the main entrance with a minimum width of 4.5 m and a head room of 5 m.

An exit may be a doorway, corridor, internal or external staircase. It can be a verandah with access to the street or the roof. It can be a horizontal exit leading to refuge area or adjoining building.

All exits shall be free of obstruction

Exits shall be clearly visible and the path to the same shall be clearly marked and sign posted. Exits shall be illuminated and wired to an independent electrical circuit.

The floors of the areas for exits shall be illuminated.

Exits shall be so arranged that that they may be reached without passing through an occupied unit.

Capacity of exits

The total population from a particular floor must evacuated in 1.5 to 2.5 minutes depending on the type of construction. The unit width for capacity of exit shall be taken as 50 cm. The number of people for different occupancies at or near the same levels and the number per unit exit width for different occupancies is also given.,

Horizontal exits shall be provided in certain occupancies. Horizontal exit is an arrangement which allows alternate egress from one floor to another floor in an adjoining building or an adjacent part of the same building.

Travel distance

The distance from any point to the final exit shall not be less than 22.5 m for residential occupancies. For others it should not be less than 30m. Wherever more than one exit is required thy shall be placed as remote as possible in opposite directions

Number of exits

All buildings shall have minimum two exits in the form of enclosed staircases. opening to the open space Every doorway shall open into corridor leading to an exit or to an enclosed staircase. Exit doorways shall open outwards, i.e. away from the room but shall not obstruct the travel along the passageway except where there is a central corridor when the door can open inwards. Exit doors shall not open on to a staircase. Exit doorways shall be openable without a key. Mirrors shall not be placed in the path of exit doorways.

Corridors and passages shall be of width not less than the doorways.

Internal staircase

A staircase shall not be arranged around a lift shaft. No gas piping shall be laid in the stair case. Minimum width has been specified for different occupancies and it should not be less than one metre.

The minimum head room shall be not less than 2.2 metres. The main staircase and internal one shall be continuous from ground to terrace.

External staircase.

Entrance to the external staircase shall be remote from the internal one. It shall not be inclined at more than 45 degrees.

Exit signs and the floors shall be properly illuminated at all times with independent electric supply or other means.

These requirements are applicable to all occupancies. Additional requirements for individual occupancies have also been specified.

For the safety of the general public and the occupants it is imperative that the architect provides for all the exits as mandated and the fire services check these points before construction is started.

It is equally important that the municipal body checks periodically that the exits are uncluttered and permits uninterrupted travel towards the exit.

(The author is U.N. Consultant on Building Codes)


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Printable version | Jul 25, 2021 12:08:40 PM | https://www.thehindu.com/life-and-style/homes-and-gardens/basic-exit-requirements-in-high-rises-public-buildings/article28204466.ece

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