HEATING AND VENTILATION.
Of the many questions that merit attention and study in connection with
the Turkish bath, all sink into insignificance by the side of that of
the _heating_ and the _nature of the heat_ supplied in the sudatory
chambers. Other things being equal, it is, after all, the _heating_ that
distinguishes one bath from another on the score of excellence. The
heating of the "bath" is the Alpha and Omega of the whole matter.
There are two ways in which heat may be applied to the body--by direct
radiation, as from the sun or an open fire; and by convection, as
through a volume of air.
The ancient Roman bathers, with floors below them which rested upon
_pilæ_, or little pillars of brick or tile, around which the flames and
hot gases from the furnace played, and surrounded by heated, hollow
walls, evidently submitted themselves to the action of a heat that must
have been of a purely radiating character.
So, also, in a less perfect manner, the Turks, who employ flues running
beneath the floors, and the Moors, who adopt stoves visible to the
bathers.
Theoretically, radiant heat in a bath is vastly superior to that which
is transmitted to the body through the medium of the air. Its virtues
have been extolled by David Urquhart and other eminent authorities on
the bath. "There is a difference," says Mr. Urquhart, "between radiating
and transmitted caloric.... I cannot pretend to treat of this great
secret of nature; to work out this problem a Liebig is required. This I
can say, that such heat is more endurable than common heat. There is a
liveliness about it which transmitted heat lacks. You are conscious of
an electrical action. It is to transmitted heat what champagne is to
flat beer.... Let us drop, if you please, the word 'bath': it is 'heat.'
Let us away with that absurdity 'hot-air': it is the application of heat
to the human frame." Elsewhere this writer has pointed out that the
terms _thermæ_, _sèjac_, and _hammâm_--the names given to the bath by
the Romans, Moors, and Orientals proper--mean _heat_, and not "hot-air"
or "hot-air bath."
My own studies, observations, and experience lead me to the conclusion
that the direction in which we shall improve the "Turkish bath" will be
in the way of providing sudatories that shall give off pure, radiant
heat in such a manner that the whole surface of the body may be sensible
of a degree of heat, while the lungs may breathe comparatively cool
air--air that has not passed over the sides of a fiery furnace and been
suddenly raised to an enormous temperature, but which has received its
heat by a gentle and gradual process of warming. Under this system the
heat of which we are sensible is as the gentle Zephyr to rude Boreas or
the biting eastern winds. If we go into a kiln of brickwork, such as is
employed in firing clay goods, after the charge has been removed and
all fumes and odours have disappeared, we shall note the soft and balmy
nature of the heat that radiates directly from the walls and vaulting.
We are, to all practical intents and purposes, _in a Roman laconicum_.
The thick walls have been highly charged with caloric during the firing
of the bricks or other articles. They have absorbed vast quantities of
heat, and are now giving off the same to the enclosed air and to
ourselves standing within. In the old Roman bath the walls were charged
with caloric by means of innumerable earthen tubes lining the sides of
the laconicum, and covered with a peculiar plaster. But in both cases
the nature of the resultant heat is identical. It radiates to one from
all sides. There is no acrid biting of the face such as one feels in the
worst type of _hot-air_ baths; no unpleasant fulness or aching of the
head; and no panting or palpitating. Such is the "bath" of pure radiant
heat, a thing totally distinct from, and altogether of a different genus
to, the bath of heated air. And one might be pardoned for the enthusiasm
which would lead one to suggest that it is only in the supplying of this
kind of radiant heat in the modern bath that true and rapid progress can
be expected, and possibly that not until this great or
partial--according as the system of radiation and convection pertains in
existing baths--revolution has been effected, will the bath, at present
used by the few, become the custom of the many. Some day, peradventure,
this hypothetical method of employing pure radiant heat may be rendered
possible and practicable, and we may be placed in a bath where we shall
receive great heat whilst breathing a comparatively cool atmosphere,
and thus receive a measure of that electrical invigoration we experience
when, in some sheltered bathing cove, we have exposed our bodies to the
fiercest rays of the morning sun whilst yet we breathe the fresh, cool,
ozone-laden air.
Till modern invention, however, has provided us with this desideratum in
the heating of the bath, we must be satisfied with existing methods. And
unless something really practical is perfected, it is far wiser to rely
upon the system of heating by convection through the air--the principle,
generally adopted, of continuously passing large quantities of
freshly-heated air through the sudatory chambers; exposing, however, the
heating apparatus, so that a maximum of radiant heat may be obtained;
and carefully guarding against injuring the air whilst raising its
temperature. If only existing baths were in perfect harmony with this
principle, one would have little cause for complaint, and might the more
leisurely await the perfecting of the true radiating principle of
heating, which I am satisfied is the one upon which we must base all our
hopes for the future of the "Turkish" bath.
For practical purposes, it will suffice if the method of heating and
ventilating a bath on the hot-air principle be explained. This I shall
now do, and subsequently give plans and instructions for methods of
heating and ventilating on systems where, by the exposure of the heating
surfaces of furnaces, a large proportion of radiant heat is thrown into
the hot-rooms.
The necessary appliances, and arrangements for the heating and
ventilation of a bath on the ordinary hot-air principle comprise a
furnace in its chamber, with flues or shafts supplying cold, and drawing
off the heated air, and a stokery with provisions for firing and storing
coke, &c. Too often the stokery is unscrupulously cramped, and the life
of the stoker thereby rendered anything but pleasant. Its design is a
simple matter, and perhaps for this reason neglected. The arrangement
and construction of the furnace chamber requires care, and the selection
of a stove or furnace great judgment. As regards the latter feature, the
most important point to consider is the nature of the heating or
radiating surfaces. What will raise the air to the required temperature,
without in the process depriving it in any way of its vitalising
elements, and without adulterating it with either smoke and fumes from
leakage, or with particles of foreign matter given off from the material
employed in its construction?
There is nothing really better as a radiating surface than ordinary
firebrick. From this material a soft heat is given off, differing in
quality from that obtained from iron. An iron furnace, however, requires
less thought in design, gives less trouble in fitting up, and is cheap,
economical, and expeditious. Stoves, therefore, with an iron radiating
surface, have been largely adopted in the past, in spite of the
objection that, when super-heated, particles of metal are thrown into
the air of the hot rooms. Of iron furnaces there are many placed before
the public; but though all are doubtless suited to ordinary
requirements, there are few that are capable of creditably fulfilling
the conditions indispensable for the hygienic heating of the air of a
Turkish bath.
These conditions may be summarised as follows:--
1. A maximum of heating-surface, with a minimum of grate space.
2. Perfect immunity from the danger of leakage from the furnace into the
hot-air chamber or conduit.
3. Freedom from the defect of liability to overheat the air.
4. Inability to adulterate the air by throwing off matter from the
heating surfaces.
Such primary essentials must be constantly borne in mind by the designer
of furnaces for the Turkish bath. Their importance must be obvious to
all.
Of the many iron stoves, Messrs. Constantine's "Convoluted" stove has
been adopted the most frequently, as an eminently practical furnace for
the effective heating of the sudatory chambers. The appearance of this
stove is familiar to all architects, and it will be unnecessary, in
these pages, to minutely describe its construction.
[Illustration: FIG. 6.
View of a small Furnace Chamber, with portion of wall broken away to
show the "Convoluted" Stove.]
The method of constructing a furnace suitable for a small public bath
is, however, shown at Fig. 6. The excavations for stokery and heating
chamber being completed, and the position of the furnace determined a
solid foundation of concrete must be prepared, upon which the brickwork
to support the stove must be laid. At the same time, the foundations for
walls of furnace chamber, stokery, coke store, and the side walls for
the horizontal cold-air conducting flues will be prepared. These latter
must then be built in half-brick with glazed interior face, and the
furnace inclosed in similar work, as shown in perspective sketch. The
flues must be covered with York stone slabs 3 in. thick, up to within
three inches or so of the convolutions of the stove, at which distance
the side walls of the furnace must be erected, the back one similarly,
and the front one round the four projecting doors, which are,
respectively, the ash-pit door, the fire door, and two doors for
cleansing the horizontal smoke-box and interior of convolutions. The
furnace walls must be continued up to a few inches above the bend of
iron smoke flue, and then--if, as shown, the furnace be small--covered
with a 4-in. York slab in one piece. If the furnace be large, a flat
brick arch must form the covering, as at Fig. 8, where this arch
supports the flooring of the laconicum. The openings for the admission
of the heated air into the conduit leading into the hot rooms may be
either directly above, as shown in the last-named illustration, or in
the side, as in Fig. 6, with inclined flues. As a rule, it is more
economical, in heating on the principle now under consideration, to
place the furnace below the level of the hot rooms; but if desirable to
place both on one level, the back wall of the furnace chamber becomes
the party wall of the laconicum, and it must be stopped short of the
ceiling, and the air debouched over it.
In cheap baths the interior face of furnace chamber may be of stock
brickwork; but best glazed work should be adopted in good ones. All hot
and cold-air ducts should be similarly lined with glazed ware. In
first-class work the floors of horizontal and inclined flues should be
of white glazed tiles set in cement. Manholes must be provided for
cleaning when necessary. Every portion of furnace chamber, flues,
shafts, and conduits for hot and cold air must be "get-at-able" either
by means of manholes or by long brushes. Air-tight doors must be
indicated on the plans wherever this necessity demands them.
The iron smoke-pipe from furnace must be conducted to the smoke flue,
and the connection between furnace chamber and flue hermetically sealed.
The walls for a small furnace chamber need not be more than 4-1/2 in.
thick. Large furnaces require walls one-brick thick.
[Illustration: FIG. 7.
An Air Filter.]
The cold-air flues leading from either side of the furnace must be
conducted to their respective inlets. If possible, at least two inlets
should be provided, facing different ways: this with regard to the
possibility of certain winds drawing the air out where it is wanted to
enter. The openings should be vertical, like windows, and, in cities,
furnished with a solid frame and casement, fitted with louvres of plate
glass with polished edges. Between the rebate and the casement it is a
good plan to leave a space of an inch and a half for a movable
stretcher-frame holding several layers of "cheese-cloth" to filter the
air. The construction of such an air filter is shown at Fig. 7. The
glass louvres keep out the wet, and throw off coarse particles of
falling soot; and the provision of a movable stretcher permits the
cloths to be frequently changed for clean ones--a very important point,
though little heeded, if not, perhaps, wholly ignored.
[Illustration: FIG. 8.
Plans and Section of a Furnace Chamber, &c., for a Bath on the ordinary
Hot-air Principle.]
The position of air intake is a matter of great importance, especially
in large towns. It evidently is bad to draw a supply of air from the
bottom of an area. Even the position shown in Fig. 8 is not good: the
shaft should be carried higher. The best places for the intakes are
where there is always a current of pure air blowing, and away from smoky
chimneys. Theoretically, it would seem that the higher the level of
intake the better; but in cities, by going high we get among the
belching chimney-tops, even if we escape the stagnation below. Moreover,
a high inlet with a strong wind tending to exhaust the air in the shaft
might find the architect with the cold air sweeping through his bath,
and all the heated air rushing up the supply-shaft. A large
"lobster-back" automatically turning _towards_ the wind, would in many
cases prevent such a disastrous result. Even in low-level intakes, as I
have said, trouble will sometimes arise from the same cause. This may be
remedied by providing more than one inlet, so that only the one facing
the current of air will be employed, the other being closed, which could
be effected by fixing the glass louvres, spoken of above, on pivots, and
connecting them with a rod and adjustable rack. It would be a very
simple matter to make the wind itself automatically open and shut the
louvres.
The theory of the heating and ventilation of the hot rooms requires most
careful study, and the particular scheme to be adopted in any new bath
must be well considered with respect to the restrictions of the site. At
Fig. 8, I have endeavoured to show how to make the best of what is
perhaps a bad job: the site only admits of ventilation at a back area,
it is impossible to construct flues anywhere else, and the fresh air
must be drawn from the same area. On the ground floor are cooling and
dressing rooms; the bath rooms are in the basement and the furnace in a
sub-basement, reached from a passage at the end of the stairs for the
bather. Two convoluted stoves are shown in a vault; three air-inlets are
provided, and the foul air is drawn up into the smoke flues, two in
number, which, above, could join one another. Let us follow the air in
its passage through the bath. Entering at the intakes, any coarse
impurities are thrown off by the smooth louvres, and the tendency of
finer particles to rush in is checked by the stretched canvas
cheese-cloths. Thus deprived of its actually visible impurities, the air
passes through a longer or shorter conduit of glazed brickwork until it
reaches the horizontal flues running to beneath the furnace walls, along
which it is rapidly drawn, and, ascending between the walls and heating
surfaces and between the two adjacent heating surfaces, absorbs the
radiating heat and enters the laconicum by way of the rectangular shaft
constructed above the vault spanning the two stoves.
Questions of temperature I will omit for the present. The air, on
passing through the laconicum, will be practically pure, as it is in
such great bulk compared with the number of occupants of this
highly-heated chamber, and it will not be absolutely necessary to
provide ventilators. These should commence in the calidarium, and
should, in the scheme of ventilation here considered, be so disposed
that the nearer they are to the lavatorium and shampooing-room, the more
frequent will they become. The object of this disposition of outlets for
vitiated air is, that the cross currents thus created may not interfere
with the main flow from the heating chamber to the lavatorium. Were too
many ventilators to be placed near the hotter end of the sudatorium,
this stream would be diverted. Too much of the freshly-heated air would
flow out at these points, and the onward movement of the air would be
enfeebled. There would then be difficulty in maintaining the temperature
in the tepidarium and lavatorium.
In passing onward through the various rooms, two changes are wrought in
the air: it loses so much of the caloric with which it is charged for
every foot it travels, and it becomes laden with the exhalations from
the lungs of the bathers. A large proportion of carbonic acid is thrown
into the air, and as the normal temperature of the human body remains,
in a healthy person, at about 98° Fahr., and rises but a few points even
when submitted to the action of heat, these exhalations, in addition to
being heavier than air, are very much below the average temperature of a
sudatory chamber. Consequently they fall, and must be extracted at the
floor level.
The total area of the outlets for vitiated air should be about equal to
the area of the narrowest part of the shaft that conducts the fresh, hot
air from the heating chamber. Thus, supposing the latter to be 5
superficial feet, and the size of outlet ventilators a clear 12 in. by 3
in., there may be 20 ventilators disposed round the bath-rooms, say 4 in
the calidarium, 7 in the tepidarium, and 9 in the combined shampooing
room and lavatorium.
In the diagrams at Figs. 8 and 9 the foul-air conduit is the space
comprised under the marble-topped benches running round the hot rooms.
At the end of the laconicum they enter flues, which I have shown as
running side by side with the smoke flues.
Other methods of heating the air, besides those mentioned, include coils
of iron flue-pipes in a brick chamber--a principle that has been
frequently adopted in the past--and plain cylindrical iron radiating
stoves, such as employed at the Hammam in Jermyn Street.
[Illustration: FIG. 9.
Section of Hot Room, showing Foul-air Conduit.]
In the latter plan, however, a great expense is created by the large
number of furnace-fires to be kept constantly burning. An exposed stove
in a hot room, has, moreover, the objection to its use that it re-heats
the air in the bath, which should never on any account be done.
If the iron stove-pipe system is adopted, a furnace similar to the one
shown at Fig. 10 must be provided, and after an additional few feet of
brick flue the iron pipe would commence and turn back upon itself much
as the flue in the fire-brick furnace. Proper supports must be
provided, and the pipes must be stout and jointed together with
expansion joints, otherwise considerable difficulty will be found in
keeping a long length of flue pipe perfectly free from leakage. Furnaces
on this principle may be designed so that they throw a certain amount of
radiant heat direct into the hot-rooms, and they possess this advantage
over a mere stove, that they warm the air more gradually. The furnace
should be built adjoining the laconicum, the partition wall being of
4-1/2-inch glazed brickwork, having a large number of small openings
made therein by leaving void spaces as described further on for the
fireclay heating apparatus. Behind this wall the iron flue-pipe should
be placed, turning back upon itself, as described above, for perhaps
half-a-dozen times, and ending in the vertical brick flue. The furnace
itself should be of fire-clay, and so designed that its utmost heating
power may be economically employed in warming the incoming air, which
should pass over the furnace and iron flues, through the holes in
partition wall, and thus into the hot rooms. The flue, if of wrought
iron, should be rectangular in section, but if of cast-iron it should be
round.
The most economical way of obtaining a high temperature in a small,
inexpensive, and unpretentious private bath is by means of a common
laundry stove, with a longer or shorter length of iron flue in the
apartment. This is the cheapest and quickest method of raising the
temperature of a room for sudorific purposes.
[Illustration: FIG. 10.
A Fireclay Heating Apparatus.]
To turn to methods of heating from a radiating surface of firebrick, at
Fig. 10 I have given the plan, elevation, and sections of a fireclay
heating apparatus. It is constructed wholly of fireclay--fireclay
bricks, quarries, and cement. In the main it consists of a long flue of
firebricks and slabs, which coils backwards and forwards over itself
till the desired amount of radiating surface is gained. Between the
coils are spaces for super-heating the air already warmed by passing
over the actual furnace and into the warm air chamber, the air passing
through by means of perforated bricks. The illustration shows a simple
furnace; but it would be an easy matter to improve upon this by
providing iron air-tight doors lined with fireclay, for cleansing flues
and air-chambers. The example given is only suited to heat a small
public bath. For a large set of hot rooms, a compound apparatus could be
constructed by placing an additional furnace in a sub-basement, the one
on the level of the sudatory supplying radiant heat, and the lower one
hot air. Two such apparatus might be placed one behind the other, end to
end, or might form the _sides_ of the laconicum; the last plan, however,
being the least to be recommended, as in such positions they would not
directly radiate their heat into the adjoining hot rooms.
The advantage of such a furnace as that shown is that it supplies
radiant heat of a most exhilarating kind, besides a proportion of heated
air, and from a fireclay surface, the employment of which renders it
absolutely impossible to overheat the air, or to contaminate it by
deleterious particles resulting from the decomposition of metal.
Moreover, the stoking of this class of furnace requires less arduous
attention than an iron stove. Its disadvantage is that, should the
temperature of the bath be allowed to fall markedly, it requires some
time for the extra heat to be made up again. Inasmuch, however, as fires
at public baths must be kept banked up overnight, this is not a matter
of importance. It is this very slowness of increase in temperature that
constitutes the safeguard against that overheated air, the presence of
which we can, with practice, detect by the smell in so many baths. The
difficulties involved in the construction of a furnace of this nature
relate to the prevention of cracking and consequent escape of sulphurous
fumes and carbon into the air. The very simplicity of the construction
of the flues and air-chambers constitutes the chief danger, as the
chances are that, unless the architect stands by and sees every joint
made, the work will be done badly. Absolutely faultless workmanship must
be employed throughout, and the fireclay materials must be literally of
the very best and soundest description. Every single joint must be
perfectly made with fireclay cement or paste. The fireclay bricks, &c.,
must be selected with regard to the amount of indestructible silica in
the clay, consistent with hardness and toughness. Homogeneity of
material must be obtained, having regard to expansion and contraction.
The same material used for the bricks, &c., worked into a paste, must be
employed for the joints.
The design for a furnace on the principle shown at Fig. 10 must be
prepared with constant regard to expansion and contraction in heating
and cooling. Should this warning be disregarded, fractures will result.
It will be seen, upon reference to the plans, that the block of flues
and air spaces is left quite free, to allow of any expansion, the
connection with the smoke-shaft being by means of an iron flue-pipe,
which, being provided in considerable length before passing through the
party-wall of laconicum and stokery, by its flexible nature permits any
slight movement in a vertical direction. If an "expansion" joint were
provided, there would be a sufficient length of iron pipe if it passed
direct from the junction with the heating apparatus into the stokery. So
much of the iron flue as is in the laconicum must be coated with
asbestos or some composition, or the heating will not be wholly by
firebrick. The junction of iron flue and heating apparatus is shown by a
cast-iron cap sliding over a projecting rim of fireclay, moulded into
the last quarry cover, similar to the way in which cast-iron mouthpieces
are fitted to retorts.
This heating apparatus is shown visible in the laconicum, but if thought
desirable it could be screened by a wall of glazed bricks--9 in. and
miss 4-1/2 in. The 4-1/2 by 3 in. holes can be arranged in diamond
patterns. This screen wall, however, cuts off a large quantity of
radiant heat.
The first flue past the actual furnace--shown with ordinary dead-plate,
raking fire-bars, ashpit, fire-door, and ashpit door for regulating
draught--has walls 4-1/2 in. thick; above, smaller bricks, 3 in. wide;
but in a larger apparatus, 9 in. and 4-1/2 in. respectively would be
required. The quarries between flues and air spaces are 24 in. by 24 in.
by 3 in., with rebated joints. Larger covers would be more liable to
crack at any provocation.
In addition to heating by means of furnaces, steam-heating may be
employed, if found, as in many cases it would be, convenient and
economical. The chief disadvantage of this method of heating Turkish
baths, is the constant danger, however slight, of bursting a pipe in
the heating coil, which, by immediately filling the highly-heated
atmosphere with vapour, might prove most disastrous to the occupants of
the hot rooms, who would be seriously scalded. Nevertheless, the
principle has been largely employed in the heating of the most recent
Turkish baths in Germany.
If adopted it may be either on the hot-air or radiating plan, as in
heating by means of furnaces. In the first method the fresh air is
introduced into a chamber containing a coil of steam-pipes, and passes
thence into the laconicum by a shaft or conduit, as in the case of air
heated by a stove. In the second method, steam radiators--compact
batteries of pipes--must be placed in recesses in the hot rooms, fresh
air being introduced over them. The steam-pipes employed should be of
the "small bore" type, about 5/8 inch internal diameter, and of wrought
iron or copper. In order to ensure as far as possible against the danger
of explosion, the system of pipes should be tested, when fixed, by
severe hydraulic pressure.
It is certainly a great advantage, in point of ease and economy, to be
able to warm a building, drive machinery, and heat Turkish and Russian
baths from one boiler, which can readily be done, very ordinary
pressures of steam giving sufficient heat to keep the radiators of the
requisite temperature. But the nature of the heating accomplished by
means of steam-pipes is very inferior to that from large radiating
surfaces of firebrick.
The average temperatures of a public bath should range from about 110°
in the shampooing rooms to 250°-260° in the hottest part of the
laconicum, taking the readings of the thermometer at a level of 6 ft. 6
in. above floor-line. Between the entrance of the heated air and its
point of furthest travel in the shampooing rooms, the bather should be
able to select any temperature that may be most agreeable to him, and as
many find by experience that a certain degree of heat is best suited to
themselves, it shows attention to the _habitués_ of the bath, if the hot
rooms are carefully maintained at the same uniform temperatures
throughout the year. This may be 110°-120° in the shampooing rooms, 140°
in the tepidarium, 180° in the calidarium, and 250° in the laconicum.
These must be the maxima of the average temperatures of each room at 6
ft. 6 in. above the floor. In a pure atmosphere the highest temperatures
are comfortable, but in a foul one they become insupportable.
In a good bath, where there is a rapid and continuous flow of air, there
will be comparatively little difference between the temperature at say 4
ft., 6 ft., and 8 ft. above the floor. In badly-ventilated rooms, where
the air stagnates, there will be a considerable difference. And here we
may note a serious objection to the heating of a bath by convection; for
while the head may be in a high degree of heat the feet are in
comparatively cool air, whereas, if possible, it should be just the
reverse. In convected heat, this of course applies in its entirety, as
where so-called radiant heat is employed the evil is not quite so
marked. And here, too, we may note the admirable nature of the Roman
system of heating, where the floors radiated the majority of the heat,
and the walls a slightly less amount. The fresh air under the ancient
system must have entered through the cooler rooms, and being drawn
towards the _calidarium_ found its exit through the ceilings, at times
by way of the regulating device mentioned by Vitruvius. Thus the ancient
bather would not suffer the inconvenience that accrues to the bather in
the modern hot-air bath, whose head, when he is standing upright, is in
a considerably higher temperature than any other portion of his body.
The temperature of a bath should not be regulated by the firing of the
furnace. This should be regularly stoked, and kept at one uniform
heat-giving condition. Bad firing and forced firing may crack the stove
should it be of iron, and the air may be overheated. The temperature
should be regulated by means of the hit-and-miss ventilators at the
floor level. Fanlights between the various hot rooms, with screw-rod
adjustment, serve as a means for regulating their relative temperatures.
The heating power of furnaces must be studied. Having calculated the
cubical contents of the rooms to be heated, and given the heating power
of the stove or apparatus to be employed per cwt. of metal or
superficial foot of radiating surface, we arrive at the necessary size.
Messrs. Constantine give the following tables to show the heating power
of the "Convoluted" stove. The figures give the requisite size of stove
to raise the air to about the relative temperatures I have mentioned
before, and with ordinary firing.
Weight of Sq. ft. of Area capable
metal. heating surface. of heating.
--- --- ---
cwt. sq. ft. cub. ft.
14 35 500
20 55 1,200
22 69 2,000
34 119 3,500
36 139 5,000
45 180 8,000
50 231 12,000
56 296 16,000
When different kinds of heating apparatus are employed, their heating
power must be carefully ascertained and calculations entered into, or it
may be found necessary to resort to the costly and humiliating process
of dragging out the stove or pulling down the furnace and refitting a
larger one. This point is worth attention. Such mistakes are not
unfrequently made.
As regards the amount of air that should flow through the hot rooms, an
allowance of 40 cubic feet per head per minute should be the minimum, if
purity of atmosphere is to be maintained. In a bath, the importance of
perfect ventilation cannot possibly be over estimated, as not only has
the respired air from the lungs to be removed, but also the deleterious
exhalations from the skin which are produced by perspiration.
The allowance of 40 cubic feet per head per minute should not, if
properly distributed, cause an unpleasant draught in any part of the hot
rooms; for it must be remembered that even in a highly-heated atmosphere
a waft of air of the same temperature is felt to be cold. The main thing
to be studied in this provision of a large volume of air is that the
cold inlet be ample, and the passage from this intake to the point
where the air is debouched into the laconicum equally roomy and
unobstructed. The rapidity of flow will depend upon the means provided
for the extraction of the foul air. With large horizontal flues, and a
capacious and tall shaft, the so-called natural system of ventilation
will be as effective as could be desired. Greater extraction power is
gained if in the brick stack a smoke-pipe can be placed running up the
whole height. In many cases mechanical ventilation could be employed
with the greatest benefit. A powerful air-propeller fixed at the end of
a system of horizontal flues under the floors of the hot rooms, and
running so as to exhaust, would do away with all the objectionable
odours and nastiness of many baths.
The purity or foulness of the air in the hot rooms forms all the
difference between a good bath and a bad one, which latter is infinitely
worse than no bath at all. There exist, at the present time, scores of
baths where the odours of the sudatory chambers are nauseating. Such
foulness arises from stagnation of the air. There is no continuous flow,
and the respirations and exhalations of the bathers are not removed. A
system of ventilation may be pointed out, but it is on the wrong
principle, and does not act. There is no change of air. The atmosphere
of such places becomes pestilential.
Owing to the expansion by heat, a relatively greater volume of air
enters the laconicum than the cold intake. This fact, however, does not
practically affect the arrangements for ventilation, &c. Theoretically,
however, it would seem to demand that the shaft conducting from furnace
to hot rooms should be of greater sectional area than that to the
furnace from the intake--about one-third larger--and that the total area
of outlets for the escape of vitiated air should be about midway between
the two.
The whole principle of the ventilation of the hot rooms of a Turkish
bath resolves itself, primarily, into the fact that we have to
continually remove _the bottom layer of air_. The provision of the
foul-air conduits below the floor level is equivalent to providing a
suspended floor with a hollow space under. This is just the reverse of
the principle of ventilating rooms of ordinary temperature, where we
require to constantly remove the top layer, and often actually do so
when we provide false ceilings to passages, &c.
The ventilators placed at the floor level of the hot rooms should be
actually so, and not 3 in. or 6 in. above. Long, wide gratings 6 in.
deep are preferable to those of deeper and narrower design. In theory,
indeed, the whole circumference of the hot rooms should be lined round
with gratings, thus making the sudatorium like a lidless box inverted,
into which hot air is thrown and escapes all round the bottom edges.
There is one point about the circulation of air in a set of hot rooms
that requires considerable attention, and that is the _back-flow_ along
the floor. In any bath where hot air is supplied, if the bather will
hold his linen "check" across the top of the doorway between the rooms
he will find that the air is flowing from the laconicum to the
shampooing room. If, however, the sheet be held across the lower
portion of the doorway, he will find that there is a current of air
setting in an opposite direction--from the shampooing room to the
laconicum. This is shown at Fig. 11.
[Illustration: FIG. 11.
Longitudinal Section of Sudatory Chambers.]
It will be seen from the diagram that the bather is really in this
back-flow when he is standing between and in a line with the doors of
the hot rooms. All the air appears to be travelling along the top of the
bath, and the bather reclining on the marble-topped benches would seem
to be bathed in air that has passed along the top of the bath, round the
shampooing rooms, and back along the floor. In reality, however, it is
only from door to door that the currents exist exactly as shown at the
diagram, Fig. 11, there being a secondary circulating process in each
room.
This circulation of air will exist in any bath heated on the modern
system--that is to say, where freshly-heated air is passed in in
sufficient quantity. It is a natural result, and tends to distribute the
heat more equally. The back-flow is only objectionable when a door is
opened direct from the heated shampooing rooms to a cooler apartment, as
the plunge bath chamber. The bather standing in a line between the
doorways may then feel a cold draught. To guard against this, double
doors, with a small lobby between, should be provided to any means of
communication with a cold chamber.
A set of hot rooms could be constructed so that the bather would be in
the top current of air that flows from the heating apparatus. By
reference to Fig. 11 the reader will understand that by the provision of
a platform or grating midway between the floor and ceiling this end
would be attained.
The atmosphere of the sudatorium must be perfectly free from vapour.
"Perfect dryness of the air," says Mr. Urquhart, "is indispensable to
the enduring of a high temperature.... This dryness is further requisite
for electrical isolation. With vapour in the chamber an atmosphere is
created injurious to health and conducive to disease. It is the very
condition in which low, putrid, and typhus fevers flourish. The
electrical spark will not ignite in such an atmosphere, and the magnet
will lose its attractive power. We all know the difference of our own
sensations on a dry and on a damp day."