because there must be a furnace and furnace flue, and the flue used is
generally that built for an open fire only; and second, the pipes are
carried in every direction, to be as much out of sight as possible. By
this means they are constantly liable to produce spontaneous ignition,
for there appears to be some chemical action between heated iron and
timber, by which fire is generated at a much lower temperature than is
necessary to ignite timber under ordinary circumstances. No
satisfactory explanation of this fact has yet been given, but there is
abundant proof that such is the case. In heating by hot-water pipes,
those hermetically sealed are by far the most dangerous, as the
strength of the pipes to resist the pressure is the only limit of the
heat to which the water, and of course the pipes, may be raised. In
some cases a plug of metal which fuses at 400 deg. is put into the pipes,
but the heat to which the plug is exposed will depend very much on
where it is placed, as, however great may be the heat of the exit
pipe, the return pipe is comparatively cool. But even where the pipes
are left open, the heat of the water at the furnace is not necessarily
212 deg.. It is almost needless to say that 212 deg. is the heat of boiling
water under the pressure of one atmosphere only; but if the pipes are
carried sixty or seventy feet high, the water in the furnace must be
under the pressure of nearer three atmospheres than one, and therefore
the heat will be proportionately increased. Fires from pipes for
heating by hot water have been known to take place within twenty-four
hours after first heating, and some after ten years of apparent
safety.
The New Metropolitan Building Act prescribes rules for the placing
steam, hot-air, and hot-water pipes at a certain distance from timber;
but as it must be extremely difficult for the District Surveyors to
watch such minute proceedings, it becomes every one who is anxious for
safety to see that the District Surveyors have due notice of any
operation of this kind.
Another cause of fire which may come under this head is the use of
pipes for conveying away the products of combustion. Every one is
acquainted with the danger of stove pipes, but all are not perhaps
aware that pipes for conveying away the heat and effluvia from
gas-burners are also very dangerous when placed near timber. It is not
an uncommon practice to convey such pipes between the ceiling and the
flooring of the floor above. This is highly dangerous. Gas-burners are
also dangerous when placed near a ceiling. A remarkable instance of
this took place lately, where a gas-burner set fire to a ceiling
28-1/2 inches from it.
Another evil of furnaces is, that the original fireplace is sometimes
not large enough to contain the apparatus, and the party wall is cut
into. Perhaps it may be necessary to notice at this point the use of
gas, as it is becoming so very general. Gas, if carefully laid on, and
properly used, is safer than any other light, so far as actually
setting fire to anything goes, but the greater heat given out so dries
up any combustibles within its reach, that it prepares them for
burning, and when a fire does take place, the destruction is much more
rapid than in a building lighted by other means. Gas-stoves, also,
from the great heat given out, sometimes cause serious accidents; in
one instance, a gas-stove set fire to a beam through a two-and-half
inch York landing, well bedded in mortar, although the lights were
five or six inches above the stone. This is mentioned to show that
gas-stoves require quite as much care as common fires.
_Spontaneous ignition_ is believed to be a very fruitful cause of
fires; but, unless the fire is discovered almost at the commencement,
it is difficult to ascertain positively that this has been the cause.
Spontaneous ignition is generally accelerated by natural or artificial
heat. For instance, where substances liable to spontaneous ignition
are exposed to the heat of the sun, to furnace flues, heated pipes, or
are placed over apartments lighted by gas, the process of ignition
proceeds much more rapidly than when in a cooler atmosphere. Sawdust
in contact with vegetable oil is very likely to take fire. Cotton,
cotton waste, hemp, and most other vegetable substances are alike
dangerous. In one case oil and sawdust took fire within sixteen hours;
in others, the same materials have lain for years, until some external
heat has been applied to them. The greater number of the serious fires
which have taken place in railroad stations in and near London have
commenced in the paint stores. In a very large fire in an oil
warehouse, a quantity of oil was spilt the day before and wiped up,
the wipings being thrown aside. This was believed to have been the
cause of the fire, but direct proof could not be obtained. Dust-bins
also very often cause serious accidents. In one instance, 30,000_l._
to 40,000_l._ were lost, apparently from hot ashes being thrown into a
dust-bin.
These accidents may in a great measure be avoided by constant care and
attention to cleanliness, and where paints and oils are necessary, by
keeping them in some place outside the principal buildings. Dust-bins
should, as much as possible, be placed in the open air, and where that
cannot be done, they should be emptied once a day. No collection of
rubbish or lumber of any sort should be allowed to be made in any
building of value.
Mr. Wyatt Papworth, architect, has published some very interesting
notes on spontaneous ignition, giving several well-authenticated
instances.
_Incendiarism_ may be divided into three sorts--malicious, fraudulent,
and monomaniac. Of the former there has been very little in London for
many years. The second, however, is rather prevalent. The insurance
offices, which are the victims, protect themselves as well as they
can, but an inquest on each fire is the true mode of lessening the
evil. This is much more the interest of the public than at first seems
to be the case. In several instances where the criminals were brought
to punishment by Mr. Payne's inquests, people were asleep in the upper
parts of the houses set fire to, and in one case there were as many as
twelve or fifteen persons. This, however, is seldom stated in the
indictment, as, if it is, the punishment is still death by the law,
and it is supposed that a conviction is more easily obtained, by the
capital charge being waived. Monomania is a rare cause of
incendiarism, but still several well-certified cases have occurred in
which no possible motive could be given. In one instance a youth of
fifteen set fire to his father's premises seven times within a few
hours. In another, a young female on a visit set fire to her friend's
furniture, &c., ten or eleven times in the course of one or two days.
In neither case could anything like disagreement or harshness be
elicited, but the reverse. In other instances, it has been strongly
suspected that this disease was the cause of repeated fires, but there
was no positive proof. In all these cases, known or suspected, the
parties were generally from fourteen to twenty years of age.
FIRE-PROOF STRUCTURES.
What is "Fire-proof Construction?" is a question which has given rise
to a great deal of discussion, simply, as it appears to me, because
the size of the buildings, and the quantity and description of the
contents, have not always been taken into account. That which may be
perfectly fireproof in a dwelling house, may be the weakest in a large
warehouse. Suppose an average-sized dwelling-house 20 x 40 x 50 =
40,000 cubic feet, built with brick partitions, stone or slate stairs,
wrought-iron joists filled in with concrete, and the whole well
plastered. Such a house will be practically fire-proof, because there
is no probability that the furniture and flooring in any one room,
would make fire enough to communicate to another. But suppose a
warehouse equal to twenty such houses, with floors completely open,
supported by cast-iron pillars, and each floor communicating with the
others by open staircases and wells; suppose, further, that it is half
filled with combustible goods, and perhaps the walls and ceilings
lined with timber. Now, if a fire takes place below, the moment it
bursts through the upper windows or skylights, the whole place becomes
an immense blast furnace; the iron is melted, and in a comparatively
short time the building is in ruins, and, it may be, the half of the
neighbourhood destroyed. The real fire-proof construction for such
buildings is groined brick arches, supported on brick pillars only.
This mode of building, however, involves so much expense, and occupies
so much space, that it cannot be used with advantage. The next best
plan is to build the warehouses in compartments of moderate size,
divided by party-walls and double wrought-iron doors, so that if one
of these compartments takes fire, there may be a reasonable prospect
of confining the fire to that compartment only. Again, cast iron gives
way from so many different causes, that it is impossible to calculate
when it will give way. The castings may have flaws in them; or they
may be too weak for the weight they have to support, being sometimes
within 10 per cent., or less, of the breaking weight. The expansion of
the girders may thrust out the side walls. For instance, in a
warehouse 120 feet x 75 feet x 80 feet, there are three continuous
rows of girders on each floor, with butt joints; the expansion in this
case may be twelve inches. The tie rods to take the strain of the flat
arches must expand and become useless, and the whole of the lateral
strain be thrown on the girders and side walls, perhaps weak enough
already. Again, throwing cold water on the heated iron may cause an
immediate fracture. For these and similar reasons, the firemen are not
permitted to go into warehouses supported by iron, _when once fairly
on fire_.
Cast and wrought-iron have been frequently fused at fires in large
buildings such as warehouses, sugar houses, &c., but according to Mr.
Fairbairn's experiments on cast iron in a heated state, it is not
necessary that the fusing point should be attained to cause it to give
way.[A] He also states, that the loss of strength in cold-blast cast
iron, in a variation of temperature from 26 deg. to 190 deg. = 164 deg. Fahr., is
10 per cent., and in hot-blast at a variation of from 21 deg. to 190 deg. =
169 deg. Fahr., is 15 per cent.; now if the loss of strength advances in
anything like this ratio, the iron will be totally useless as a
support, long before the fusing point is attained.
Much confidence has been placed in wrought-iron tie or tension rods,
to take the lateral strain of the arches, and also in trusses to
support the beams; but it must be evident that the expansion of the
iron from the heat, would render them useless, and under a high
temperature, it would be so great as to unsettle the brickwork, and
accelerate its fall, on any part of the iron-work giving way: again,
the application of cold water to the heated iron, in an endeavour to
extinguish the fire, is almost certain to cause one or more fractures.
The brick-arching is also very liable to fall, especially if only four
and a half inches thick, independently of the weight which may be
placed upon it, for it is not uncommon after a fire in a large
building, to find the mortar almost completely pulverized to the depth
of three inches, or four inches, from the face of the wall. When a
fire occurred under one of the arches of the Blackwall Railway, on the
15th July, 1843, a portion of the lower ring fell down, and also a few
bricks from the next ring.
Another very serious objection to buildings of this description, is
that, unless scientifically constructed, they are very unlikely to be
safe, even for the common purposes intended, independent of the risk
of fire. In the Report of Sir Henry De la Beche and Mr. Thomas Cubitt
on the fall of the mill at Oldham, in October, 1844,[B] it is stated
that the strength of the iron-beams was within ten per cent. of the
breaking weight. Now according to Mr. Fairbairn's experiments on
heated iron, already referred to, an increase of temperature of only
170 deg. would have destroyed the whole building. It is quite clear,
therefore, that so long as mill-owners and others continue to
construct such buildings without proper advice, they must be liable to
these accidents. In timber-floors there can be no such risk, as the
strains are all direct, and any journeyman carpenter, by following
good examples, can ascertain the size required; and even if he makes a
mistake, the evil is comparatively trivial, as the timber will give
notice before yielding, and may be propped up for the time, until it
can be properly secured. In the case of fire-proof buildings, an
ignorant person may make many mistakes without being aware that he has
done so, and the slightest failure is probably fatal to every one
within the walls. This also increases the difficulty and danger of
extinguishing fires in a large building, as the only method of doing
so is for the firemen to enter it with their branches, and in case of
the floors falling, there is no chance of escape. On the other hand,
timber-floors have repeatedly fallen while the firemen were inside the
building, and they have made their escape uninjured.
In a pamphlet published by Mr. S. Holme, of Liverpool, in 1844,[C] and
which contains a report from Mr. Fairbairn on fire-proof buildings, it
is stated, that many people, especially in the manufacturing
districts, are their own architects; that the warehouses in Liverpool
may be loaded to one ton per yard of flooring; and that unless great
care and knowledge are used in the construction of fire-proof
buildings, they are of all others the most dangerous.[D]
The following are the principles on which Mr. Fairbairn proposes to
build fire-proof warehouses:--
The whole of the building to be composed of non-combustible
materials, such as iron, stone, or bricks.
In order to prevent fire, whether arising from accident or
spontaneous combustion, every opening, or crevice,
communicating with the external atmosphere to be closed.
An isolated staircase, of stone, or iron, well protected on
every side by brick, or stone walls, to be attached to every
story, and be furnished with a line of water-pipes,
communicating with the mains in the street, and ascending to
the top of the building.
In a range of stores, the different warehouses to be divided
by strong partition-walls, in no case less than eighteen
inches thick, and no more openings to be made than are
absolutely necessary for the admission of goods and light.
That the iron columns, beams, and brick arches be of
strength sufficient, not only to support a continuous dead
pressure, but to resist the force of impact to which they
are subject by the falling of heavy goods upon the floors.
That in order to prevent accident from the columns being
melted by intense heat in the event of fire in any of the
rooms, a current of cold air should be introduced into the
hollow of the columns, from an arched tunnel under the
floors.
There is no doubt that if the second principle could be carried out,
namely, the total exclusion of air, the fire would go out of itself;
but it seems, to say the least of it, very doubtful indeed if this can
be accomplished, and if it could, the carelessness of a porter leaving
open one of the doors or windows, would make the whole useless. The
fifth principle shows that Mr. Fairbairn has omitted to allow for the
loss of strength the iron may sustain from the increase of
temperature. The last principle would not be likely to answer its
purpose, even if it was possible to keep these tunnels and hollow
columns clear for a number of years, which is scarcely to be expected.
A piece of cast-iron pipe, one-and-a-half inch in diameter, was heated
for four minutes in a common forge, both ends being carefully kept
open to the atmosphere, when, on one end being fixed in a vice, and
the other pulled aside by the hand, it gave way.
One of the principal objections to the kind of fire-proof buildings
above described, is, that absolute perfection in their construction is
indispensable to their safety; whereas buildings of a more common
description are comparatively safe, although there may be some errors
or omissions in their construction. Indeed, Mr. Fairbairn states in
the same Report, that "it is true that negligence of construction on
the one hand, and want of care in management on the other, might
entail risk and loss to an enormous extent."
The following is a very clear proof of the inability of cast iron to
resist the effects of fire:--
"A chapel in Liverpool-road, Islington, seventy feet in length and
fifty-two feet in breadth, took fire in the cellar, on the 2nd
October, 1848, and was completely burned down. After the fire, it was
ascertained that of thirteen cast-iron pillars used to support the
galleries, only two remained perfect; the greater part of the others
were broken into small pieces, the metal appearing to have lost all
power of cohesion, and some parts were melted. It should be observed,
that these pillars were of ample strength to support the galleries
when filled by the congregation, but when the fire reached them, they
crumbled under the weight of the timber only, lightened as it must
have been by the progress of the fire."
In this case it mattered little whether the pillars stood or fell, but
it would be very different with some of the large wholesale warehouses
in the City, where numbers of young men sleep in the upper floors; in
several of those warehouses the cast-iron pillars are much less in
proportion to the weight to be carried than those referred to, and
would be completely in the draught of a fire. If a fire should
unfortunately take place under such circumstances, the loss of human
life might be very great, as the chance of fifty, eighty, or one
hundred people escaping in the confusion of a sudden night alarm, by
one or two ladders, to the roof, could scarcely be calculated on, and
the time such escape must necessarily occupy, independent of all
chance of accidents, would be considerable.
For the reasons here stated, I submit that large buildings, containing
considerable quantities of combustible goods, with floors of
brick-arches, supported by cast-iron beams and columns, are not,
practically speaking, fire-proof; and that the only construction which
would render large buildings fire-proof; where considerable quantities
of combustible goods are deposited, would be groined brick-arches,
supported by pillars of the same material, laid in proper cement. I am
fully convinced, from a lengthened experience, that the intensity of a
fire,--the risk of its ravages extending to adjoining premises, and
also the difficulty of extinguishing it, depend, _caeteris paribus_, on
the cubic contents of the building which takes fire, and it appears to
me that the amount of loss would be very much reduced, if, instead of
building immense warehouses, which give the fire a fortified position,
warehouses were made of a moderate size, with access on two sides at
least, completely separated from each other by party-walls, and
protected by iron-doors and window-shutters. In the latter case, the
probability is, that not more than one warehouse would be lost at a
time, and perhaps that one would be only partially injured.
It is sincerely to be hoped that the clause in the last Metropolitan
Building Act, restricting the size of warehouses, may be more
successful than its predecessor, for it is not only property that is
at stake, but human life. In many of these "Manchester warehouses,"
there are fifty or one hundred and upwards of warehousemen and
servants sleeping in the upper floors, whose escape, in case of fire,
would be very doubtful, to say the least of it.[E]
Covering timber with sheet-iron is very often resorted to as a
protection against fire. I have never found it succeed; but Dr.
Faraday, Professor Brande, Dr. D. B. Reid, and Mr. W. Tite, M.P., are
of opinion that it may be useful against a sudden burst of flame, but
that it is worse than useless against a continued heat.
In wadding manufactories the drying-rooms were frequently lined with
iron-plates, and when a fire arose there, the part covered with iron
was generally found more damaged than the rest; the heat got through
the sheet-iron, and burnt the materials behind it, and there was no
means of touching them with water until the iron was torn down; sheet
iron should not, therefore, be used for protecting wood.
Even cast iron, one inch thick, laid on tiles and cement three inches
thick, has allowed fire to pass through both, to the boarding and
joisting below, merely from the fire in an open fire-place being taken
off and laid on the hearth. This arises from iron being so good a
conductor that, when heat is applied to it, it becomes in a very short
time nearly as hot on the one side as the other. If the smoke escapes
up a chimney, or in any other way, there may be a serious amount of
fire before it is noticed.
In a fire at the Bank of England, the hearth on which the stove was
placed was cast iron an inch thick, with two-and-a-half inches of
concrete underneath it; but the timber below that was fired.
With regard to the subject of fire-proof dwelling-houses of average
size, I consider that such houses when built of brick or stone, with
party-walls carried through the roof; the partitions of brick, the
stairs of slate or stone, the joists of wrought iron filled in with
concrete, and the whole well plastered, are practically fire-proof
because, as stated at the opening of this chapter, there is no
probability that the furniture and flooring in any one room would make
fire enough to communicate to another. The safest manner of heating
such houses is with open fire-places, the hearths not being laid upon
timber. Stone staircases, when much heated, will fracture from cold
water coming suddenly in contact with them; but in a dwelling-house
built as described above, there is very little chance of such a
circumstance endangering human life, even with wooden steps carried
upon brick walls, and rendered incombustible by a ceiling of an inch
and a quarter of good hair mortar and well pugged, all the purposes of
safety to human life would be attained.
There is a particular description of floor, which, although not
altogether fire-proof, is certainly (at least so far as I can judge),
almost practically so for dwelling-houses. It is composed simply of
plank two and a-half or three inches thick, so closely joined, and so
nicely fitted to the walls, as to be completely air-tight. Its
thickness and its property of being air-tight, will be easily observed
to be its only causes of safety. Although the apartment be on fire,
yet the time required to burn through the floor above or below, will
be so great, that the property may be removed from the other floors,
or, more probably, if the means of extinguishing fire be at hand, it
may be subdued before it can spread to any other apartment. The doors
must of course be made in proportion, and the partitions of brick or
stone.
Before closing the subject of fire-proof structures, I will add a few
words upon fire-proof safes. These are all constructed with double
casings of wrought iron, the interstices being in some filled with
non-combustible substances, such as pumice stone and Stourbridge clay,
and in others with metal tubes, that melt at a low temperature, and
allow a liquid contained in them to escape, and form steam round the
box, with the intention of preventing the heat from injuring the
contents. Such safes I have never found destroyed; and in some cases,
after large fires, the whole of the contents have been found
uninjured, while the papers in common safes, merely made strong enough
to prevent their being broken into, were generally found consumed.
FOOTNOTES:
[Footnote A: _Vide_ Seventh Report of the British Association, 1837,
vol. vi. page 409.]
[Footnote B: _Vide_ Report on the Fall of the Cotton Mill, at Oldham,
and part of the Prison at Northleach, page 4. Folio. London: Clowes
and Sons, 1845.]
[Footnote C: _Vide_ Report of W. Fairbairn, Esq., on the Construction
of Fire-proof Buildings. With introductory Remarks by Samuel Holme,
page 11, _et seq._ Tract, 8vo. Liverpool: T. Baines, 1844.]
[Footnote D: The Author has been informed by Mr. Farey, M. Inst. C.E.,
that a fire took place, in 1827, in a mill belonging to Mr. Marshall,
of Leeds, the whole of which, with the exception of the roof, was
fire-proof. The upper floor was filled with flax, which took fire; the
roof fell in, and the heat so affected the iron beams of the floor, as
to cause them to give way.]