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Figs. 355 and 356. —Folding Door at Dundee.
COMPARTMENTS.
373
Folding doors are flexible sheetings of wood or metal, so contrived as
to be wound round a roller at the top of tlie doorway. Details of one in
use at Dundee are given in figs. 355 to 360. It is constructed of pitch-
pine laths threaded on steel wire, and fastened to an iron drum, 12 inches
in diameter. By means of balance weights and simple gearing, one man
can, with ease, lift and lower the sashes.* Kolding doors are lighter and
take up less space than sliding doors. At the same time, sliding doors are
stouter and offer a greater obstacle to the passage of fire.
The effect of fire on iron (or steel) doors is somewhat curious. Under
the influence of intense heat they curl up and twist like a piece of burning
paper. This erratic behaviour constitutes a source of peril, and some have
even gone so far as to advocate the adoption of wooden doors on the ground
that they burn away in comparative harmlessness.
Compartments.—When a shed is of considerable length, it is advisable to
divide it into a series of compartments, within any one of which an out-
break of fire can be completely confined. Division walls between adjoining
compartments should then be carried some 5 or 6 feet above the roof line,
in order to cut off all connection. Kor the same reason, any door openings
in such walls should be fitted with double doors. The system of detached
compartments, with intervening alley ways, is a greater safeguard, but it
involves less economy in space and greater expenditure in construction.
* G. C. Buchanan on ‘‘The Port of Dundee,” Min. Proc. Inst. C.E., vol. cxlix.