Standard for Fire Safety in Rapid Transit Systems - Singapore Civil ...

2.2.5.8 BASEMENT EXIT STAIRCASE
(a) Any exit staircase which serves a basement storey of
a station shall comply with all the applicable
provisions for exit staircase under Cl.2.2.5.6, and
(b) Such exit staircase shall not be made continuous with
any other exit staircase which serves a non-basement
storey of the station, and
(c) Basement exit staircases which are vertically aligned
with the exit staircases of non-basement storeys shall
be separated from such other exit staircases by
construction having fire resistance for a minimum
period equal to that required for the enclosure.
2.2.5.9 SPIRAL STAIRCASE
(a) Spiral staircases shall not serve as required exits
except that external unenclosed spiral staircases when
built of non-combustible materials and having a tread
length of at least 750mm may serve as required exits
from mezzanine floors and balconies or any storey
having an occupant load not exceeding 25 persons,
and
2.2.5.10 EXIT RAMP
(b) Such spiral staircases shall be not more than 10m
high, and
(c) Spiral staircases shall comply with the applicable
requirements of Cl. 2.2.5.6.
(a) Internal and external exit ramps may be used as exits
in lieu of internal and external exit staircases subject
to compliance to the applicable requirements of
Cl.2.2.5.6, and
(b) The minimum width and capacity of exit ramp shall
be in accordance with Cl. 2.2.3.7, Cl. 2.2.4.6 and
Cl. 2.2.5.4.
(c) The slope of such exit ramps shall not be steeper than
1 in 12, and
Basement exit
staircase
Spiral staircase
Exit ramp
Standard for Fire Safety in Rapid Transit Systems 31