Arthur Newsholme.

School hygiene: or, The laws of health in relation to school life online

. (page 3 of 10)
Online LibraryArthur NewsholmeSchool hygiene: or, The laws of health in relation to school life → online text (page 3 of 10)
Font size
QR-code for this ebook


We may practically fix the permissible carbonic acid in the
atmosphere of school-rooms as i part in 1,000, instead of the
ideal limit of '6 per i,ooo ; as it is doubtful if, with the 15 square



28 SCHOOL HYGIENE.

feet of floor space allowed (p. 9), we can get beyond this.
If the school-room be reckoned as 10 feet high, then in order
to obtain 1,500 cubic feet of air per hour, it is evident that
the air must be replaced at least every six minutes, i.e., 10
times in an hour.

/ To recapitulate : the requirements of each class-room in a
school building should not be less than 15 S(iuare feet of
floor-area per pupil, and the window-space should equal one-
fourth of the floor-space. Each pupil should be provided with
25 to 30 cubic feet of fresh air per minute, introduced and dis-
tributed without producing unpleasant draughts and having a
temperature of from 60° to 65° Fahr.

The above represents the minimum of requirement for cold
weather. In warm weather, as much fresh air must be intro-
duced as open windows and doors will admit.

A fallacy frequently entertained is that deficiencies in floor-
space rtiay be compensated by a lofty ceiling. Such is not the
case, however. A "lofty" room is not necessarily "airy."
Any height above 12 feet has little or no influence on the
purity of the lower atmosphere in which the children have to
live ; and cross- ventilation at a considerable height may leave
the atmosphere of the lower level in which children breathe in
a vitiated condition. It is not advisable to have school-rooms
much higher than the windows, as warm and impure air tends
to accuumlate along the ceiling, subsequently falling to the
floor-level as it cools.



CHAPTER Vr.



Natural Ventilation.



Rules respecting Ventilation. — Natural and Artificial Ven-
tilation. — Ventilation through Window., Wall, Chimney, ana
Ceiling.

Most treatises on ventilation and heating have been founded
on European facts and figures, and are hence unreHable for the
American climate. And even in speaking of the States alone,
it is ditificult to give general methods which shall be applicable
to the great diversities of climate included in its 25*^ of latitude,
of which the only one feature in common is the inconstancy
of the climate. New York, for instance, has been said to have
the summer of Rome, and the winter of Copenhagen.

Ventilation is constantly being produced by two natural
agencies, viz., the diffusion of gases, and the movements
caused by differences of temperature.

Diffusion, by which the purer outside gases tend to mix
with the impure internal air, is constantly going on, thougn
the rate of diffusion is under ordinary circumstances slow and
the amount of interchange thus effected is but small.

Differences of temperature cause much more active move-
ments of air, warm air floating to the top of cold air, as oil floats
to the top of water. The air in a room is wanned by the in-
mates and by the stove, gas, or other source of artificial haat.
Cold ail- tends to rush in from every opening, and, being
29



30 SCHOOL HYGIENE.

heavier than warm air, falls toward the floor, producing a
draught. The great problem of ventilation is to secure a
sufficient interchange of air without causing draughts. The
entrance of air at any temperature below 50° mto a room
whose temperature is 65 "^ or even 70" is almost certain to be
accompanied by draught; hence it is necessary to warm the
entering air during many of the winter months.

If a free entrance for pure air is not provided, the influence
of the higher temperature in the school-room may produce an
aspiration of air from undesirable places. Thus it not un-
commonly happens that air is drawn from underground cellars,
defective drains, water-closets, &c.

The following rules respecting ventilation are of importance :

(i.) The air should be drawn from a pure source.

(2.) No draught or current should be perceptible. Very often
the remedy for a draught is not to close the opening, but to
make others in order to increase the area through which air enters.

(3.) The entry of air should be constant, not at intervals.

(4.) An abundant exit for impure air should be provided
separate from the points of entrance of fresh air. In order to
maintain a given standard of purity, it is necessary to provide for
the removal of as much impure air as is supplied of pure air.

Ventilation is of two kinds, natural and artificial. The first
kind is produced by the ordinary interchange of air when
windows or doors are allowed to remain open. Artificial ven-
tilation is that produced by the extraneous help of heating
apparatus or of mechanical appliances for propelling the air
inio a room or aspirating it from it.

Such mechanical measures are not practically useful for
school-rooms, and we shall confine ourselves to the considera-
tion of ventilation by natural means and by heating a|)paratus.

Natural Ventilation is i)ossible as an exclusive plan only
during the summer months. In colder weather the admij:3ion



NATURAL VENTILATION.



31



of external air produces violent draughts. Any reliance on it as
the source of pure air is practically found to end in the careful
closure of all windows, doors, and ventilating apertures, and a
resulting foulness of atmosphere which is only too common in
school-rooms.

When the external temperature reaches 60°, or better still
65^, the air may be freely admitted. Open iin?idows are by far
the best means of ventilation, and during the school recess
all the windows should be thrown open, opposite windows if
possible or doors and windows, in order that the rooms may
be thoroughly flushed with air. Ordinary ventilation commonly
leaves a considerable proportion of organic volatile matter
from respiration hanging about the room, while the rapid
currents of air during the flushing of a room carry this away.

The occurrence of any down-draught from an open window
may be prevented by having its upper segment made to work on
a hinge, lateral triangular pieces of glass being inserted on each
side of the whidow (Fig. 4) ; or a narrow piece of wood may be




4. — Diagram of ventilation by hinged windows.



32



SCHOOL HVGirCNR.



inserted under the lower sash of the window, an upward cur-
rent of air being thus allowed between the two sashes. (Kig. 5.)




Fig. 5. — Ventilation between window-sashes, a block being fitted under
the lower sash.

Sometimes the top sash is opened and wire gauze is fastened
across, but by this plan the amount of air which enters is much
less than through a continuous opening of the same area.

The ivall may be utilised for ventilating purposes by the in-
sertion of a grating near the floor which is connected on its
inner aspect to a vertical tube, an upward direction being thus
given to the entering air. (Fig. 6 ) Or the grating may be placed



NATURAL VENTILATION.



33



higher up, a movable valve on the inner side of the wall direct-
ing the current upwards. (Fig. 7.)




Fig. 6. — Diagram showing ventilation by Tobin'S tube, aiid an exit-shaft leading
from centre-flower of ceiling.




Fig. 7.— Sheringham's ventilator.

The ventilation is much more likely to be successful if there
are openings on opposite sides of the room, or if there is a
chimney or other draught-compeller, in the school-room.

Indeed a cJiimney should always be allowed for each room,
even when it is not contemplated to have open fires. Owing



34



SCHOOI- HYGIENE.



to the aspirating effect of winds acting at the top of the chim-
ney, there is generally an up-current, and always so if there is
free ingress of air by doors or windows. The action of the
chn-nney in witlidrawing impure air from a room, may be
greatly increased by narrowing its two ends, so as to produce a
more rapid current at the entrance and exit of air.

Flap's or Arnott's valves (Fig. 8) placed above the fire-
place and opening into the flue, are of some service in with-
drawing hot impure air collected near the ceiling, though the
extent of their value must not be over-estimated, as the amoun/
of air passing through them is, on account of their size, neces-
sarily limited.



^m



KgKa




Fig 8. — Boyle's mica-flap ventilator.
a, View from room. d. View from chimney.

^ The ceiling may be utilised for carrying off foul air, and as
, the foul air from respiration is warm, it rises to the top of the
room, and may with advantage be at once removed.

A grating in the external wall may be made to correspond
to the space between the ceiling and the floor of the room
next above, and apertures in the ceiling made to communicate
with this. (Fig. 6.) Or an air-tight zinc chamber between the
ceiling and the room above may be carried, by means of a zinc
pipe, into the chimney, the junction with the latter being guarded
by a valve working only in one direction.

The use of ventilating gas-burners should always be en
forced, the products of the combustion of gas being thus at
once removed, and at the same time much impure air from



NATURAL VENTILATION. 35

the room. (Fig 3, page 20.) It is important, however, that
children should not work in a room where gas is required during
the day, and that their evening studies should be very short.

In order that natural ventilation may be more effectual, all
corridors should be large and airy, and have windows opening
direct to the outer air. No school-plan which does not fulfil
these conditions can be regarded as satisfactory.

In the methods of ventilation hitherto described, the air is
admitted at the same temperature as the external air. Such
methods have, however, but a limited application in the
States. During a large portion of the year, in order to pre-
vent dangerous draughts, the incoming air requires warming.
Th,e means by which the incoming air can be wanned will be
discussed in the next chapter.



CHAPTER Vir.

■Ventilation and Warming.

Difficulties oj Successful Ventilation by Warm Air. — Open Fire-
place. — Heating by Gas. - Closed Stoves. — Central System of
Heating. — Hot- Air Furnaces. — Steam Apparatus. — Hot- H ater
Apparatus. — Etit ranee Flues and Extraction Shafts. — 'J he
Bridgeport System.

A DOUBLE heading has been purposely made to this chapter.
In fact, ventilation and warming, to be in accordance with the
laws of health, always require to be conjointly considered. A
successful system of warming a school must necessarily, for
purposes of health, provide pure air ; and a successful system
of ventilation must, at least in the winlcr months, also furnish
warmth.

These considerations bring us f:ice to face with the serious
question of expense. The wanning of a large volume of air
means the expenditure of coal or gas, and ventilation means
the discharge of this warmed and the refo7-e expensive air as soon
as it becomes impure. If, in order to diminish expense, no
provision is made for the escape of the warm air as it becomes
polluted, the school-room speedily becomes loul and unhealthy,
— a very hot-bed of disease.

When the necessary expensiveness of ventilation is faidy
grasped by school-managers, surely there will be an end of the
economising over ventilation which is now so general. Such
economising is most certainly at the expense of the children's
health, and tends yearly to greatly increase our bill of mortality.
36



VENTILATION AND WARMING. 37

No system of warming and ventilation has been devised
which will work automatically without the supervision of a
competent officer. Brains are required as well as coal and an
apparatus for this purpose ; a watchful and intelligent super-
vision to see that the temperature and the ingress and egress
of air are properly adjusted.

The school-keeper, who is generally responsible for the
maintenance of hot-air apparatus, not uncommonly regards
ventilation as inimical to his interests, and will, in case the
heat is lowered, stop the valves leading to the exit-flues, thus
penning up the hot impure air, rather than apply the extra fuel
required. It is to his interest to appear economical of cgal ;
he is, therefore, under the constant temptalion to check the
outflow of warm air from the rooms, and to minimise the
period of flushing them with external air after school hours.

The system of warm air ventilation to be used will vary
with the size of the school and with local conditions. For
small schools some of the following plans may be adopted,
though in large schools a central system is the best.

The Open Fire-place not only furnishes a cheerful warmth, but
is likewise a valuable purifier of the atmosphere of a room, as
from 14,000 to 20,000 cubic feet of air pass up an ordinary
chimney each hour. Thus, reckoning 1,500 cubic feet for
each scholar, the respiratory impurities of from 9 to 13
scholars can be got rid of in this way. The open fire-place,
however, docs not form a convenient source of heat except lor
small rooms, for the following reasons : — (i) The heat is un-
equally distributed, being, for instance, 9 times as great at a
distance of one foot from the fire as it is at a distance of 3 feet.
(2) Currents of cold air are produced along the floor in order
to supply the place of the air which is rushing up the chimney.
These are very trying unless a free supply of warm air from
some other source than the fire is allowed. (3) There is the



38



SCHOOL HYGIENE.



trouble of frequently replenishing the fire, interfering with
studies.

The great loss of heat necessarily involved in an open fire-
place has led to the use of chambers behind the fire-place, by
which external air is warmed as it enters the room. A stove
constructed on this principle is shown in Fig. 9. At the back
of the stove is an air-chamber communicatincr with the external



Air admitted through the opening {a, Fig. 9) is warmed by
coming in contact with the fire-clay {d), which separates the air-
channel from the smoke flue {c). The warmed air leaves the
air-channel by the grating (fe) over the fire-place, and then
travels along the upper part of the room, falling to the floor as
it cools and finally escaping up the chimney.







Fig. 9. — Slow-combustion ventilatins: stove.
I. — Section of stove, showing — a, entrance of cold air ; b, entrance of

warmed air into room ; c, smoke-flue ; d, fireclay back of stove.
8. — Front elevation of same stove.



VENTILATION AND WARMING.



39



Gas is sometimes employed instead of coal for fires.

No gas-stove should be allowed in which provision is not
made for carrying off all the products of combustion. A
chimney or pipe for carrying away the gases produced is even
more necessary than in the case of a coal-fire, for in the latter
case the smoke produced would necessitate a recourse to open
windows or other means of ventilation, while in the former the
deleterious products are invisible. Gas is suitable as a means
of heating only small rooms, owing to its greater expense.
Several stoves are convenient and thoroughly sanitary ; they
are placed in an open fire-place with a flue-pipe attached. For
school-rooms where gas is, for special reasons, employed as the
heating agent, the Calorigen stove is a valuable means of
supplying warm and pure air. Its arrangement is shown
in Fig. lo. A spiral tube communicates below with the




Fig. io. — The Calorigen stove.



40 SCHOOL HYGIENE.

external air, and opens at its upper end into the room. A
small gas-tlame is kept burning below the spiral tube, the pro-
ducts of combustion from which are carried directly out-of-
doors. The heat thus produced warms the air which is
passing along the spiral tube and causes a constant rapid entry
of warm air into the room.

Closed Stoves are useful chiefly in small school-rooms, either
gas or coal being burnt. They possess the advantage over an
open fire-place, that there is a smaller consumption of fuel, and
that the combustion can be more effectually regulated.
Commonly, however, they make the air of a room dry, and
produce a peculiar close smell, probably owing to the charring
of minute organic particles. It is found also that carbonic
oxide may pass through cracks or even through the substance
of iron stoves, when they are red-hot. When stoves are
employed, firebrick should be everywhere in contact with the
fire, and the stove should never be allowed to become red-hot.
There should be as few joints as possible, and these should be
horizontal and not vertical. The supply of air to the stove
should never be cut off, nor should the escape of the
products of combustion be prevented by dampers, or by
admitting air between the stove and the chimney.

We are strongly of opinion that stoves should be allowed
only in combination with some provision for warming the in-
coming air. This may be secured by having a sheet iron or
zinc cylinder, considerably wider than the stove-pipe, placed
round it and fastened to the floor below. A good-sized pipe is
then carried through the floor and out to the external wall of
the school. In this way a large supply of warmed air is
drawn into the room (Fig. ii). Similarly the stove-pipe may
be utilised by enclosing it in another pipe, which starts some
distance from the stove, and is carried into the chimney. This
causes the abstraction of considerable impure air. If required.



VENTILATION AND WARMING.



4T



impure air may be withdrawn from the next room below by a
modification of this method.




Fig. II. — Closed stove arranged to warm incoming freshair.

Central Syi>iem of Heating.— Yioi air, steam, and hot water
are the usual sources of heat employed, and each plan will
require consideration.

Tlie great majority of Hot-air Furnaces are unsatisfactory
for several reasons. — (i.) The furnace is generally too small ;
consequently, in severely cold weather, the radiating surfaces
are unduly heated .^nd the joints may be loosened. Carbonic
oxide and sulphurous acid may then escape, the latter being
fortunately irritant, but the former odourless and recognised
only by the giddiness, languor, and peculiar discomfort



42 SCHOOL HYGIENE,

produced. Carbonic oxide will pass through red-hot cast-iron,

but the danger from the sand-holes produced in defective
casting, or from badly-fitting joints, is probably much greater.
Wrought-iron furnaces do not allow the escape of carbonic
oxide through their substance, but the joints may crack ; and
wrought-iron oxidises more rapidly than cast-iron.

(2.) No provision is made for mixing cool with the heated
air, which is often distributed at 140°. To cool the room the
register is shut off, the poor scholars being then obliged to re-
breathe the same atmosphere repeatedly.

(3.) The source of the air supply to the furnace is often
most unsatisfactory. The furnace-room may contain decom-
posing vegetables or an empty bell-trap leading to a defective
drain or a water-closet, none of which increase the purity of
the school atmosphere. If the furnace-room is underground,
it is not infrequently kept closed, and then the air which is
warmed may be the air already breathed by the scholars, and
subsequently drawn down into the cellar. A large furnace
is best, as it never needs to be made red-hot. It should have
the fewest joints and the largest amount of radiating-sur-
face, in proportion to the size of the fire-box, that can be
secured.

Steam Apparatus is perhaps more frequently used than any
other in the United States ; and it offers such great advantages,
that it is to be regretted that it is not more frequently used in other
countries. It is much more easily made to work and is cheaper
than hot-water apparatus, and there is less difficulty in planning
it. Also the radiating surfaces, being at a higher temperature
than with hot water, may be made smaller and more compact.

Its chief disadvantages are that (i) constant attention is
required to keep up the supply of heat, as the radiating sur-
faces cool much more rapidly than hot-water apparatus.
(2; The radiators being at a very high temperature it is dilfi-



VENTILATION AND WARMING. 43

cult to regulate the supply of heat in accordance with the out-
door temperature.

This may be remedied by arranging each set of radiators in
several different sections, in each of which the flow of steam
can be regulated independently of the others. Or the air
ducts and flues may be so arranged that by movement of a
valve the air can be made to pass wholly in contact with the
radiating surfaces or separate from them in any proportion.
Such a plan requiries the superintendence of a skilled
attendant.

Hot-wakr Apparatus possesses some advantages over steam-
apparatus, in the facts that the air passing over hot-water pipes
is as a rule not raised above ioo° F., with a temperature of the
pipes of from 160-180°, and that hot water continues to cir-
culate some time after the fire is extinguished.

We shaU mention only to condemn the system of ^''Direct
Radiation" in which steam-pipes are placed in a room without
any provision for the entry of warmed air. This has been
well described as " one of the most killing systems in exist-
ence." The use of hot-water pipes (apart from arrangements
for ventilation), whether on the low-pressure or high-pressure
system, is similarly to be condemned. In every case provision
should be made for passmg the cold external air over the pipes
as it enters the room.

In discussing the preceding systems of warming, we have
assumed that warmed air is admitted in amount proportionate
to the number of scholars. Each scholar requiries 1,50c
cubic feet of air per hour ; therefore, assuming the space per
head as 150 cubic feet, it follows that the air of the room must
be replenished every 6 minutes. At the same time an equal
(or slightly larger) amount of air must be removed to make
way for the pure air.

Suppose we have to arrange for a school with from 8 to la



44 SCHOOL HYOIF.NE.

classrooms, each with 40 to 60 pupils, and that these are in
connection with a large central hall in a two-story brick build-
ing. Ordinarily, architects concern themselves entirely with
the provision of extraction-shafts for foul air, trusting for pure
air to what can enter through slits in the window-sills, &c.,
while the heating-apparatus is apart from any ventilation.

The provision of these extraction-shafts is of great import-
ance, and we may consider them first. As a rule there should
be an aspirating shaft or chimney on each side of the central
hall. A room containing 50 scholars, should discharge 2;
cubic feet of air per second ; a flue carrying air with a velocity
of 6 feet per second should therefore be 2 feet square, exclusive
of the space allowed for smoke-flue or other heating apparatus.
(Dr. Billings.) Such extraction, however, without the provi-
sion of warm pure air to take its place, is never satisfactory.
The vis a tergo as well as the vis a f route is required in order to
maintain a pure atmosphere. The system adopted at the High
School, Bridgeport, Connecticut, is one of the most successful
and complete hitherto adopted, as it fulfils all the requirements
of school ventilation and warming. (For details see 3rd
Annual Report of Connecticut State Board of Health.)

In this system the coil boxes heated by steam are placed
on the inner wall, extensive piping being thus saved and the
danger of freezing obviated. Fresh air is passed through the
coil-chambers and conveyed to the rooms by metallic flues
entering the inner wall about 8 feet from the floor. Thence it
diffuses itself along the walls and ceiling, passing down the
opposite wall and returning at a lower level to the flue for exit
of impure air, which is placed under a platform measuring 6 by
12 feet on movable castors and on the same side of the room
as the introduction-flue.

Careful experiments have shown that no other relative posi-
tion of entrance and exit flues ensures so thorough and equable



VENTILATION AND WARMING. 45

a warming of the room, and replenishing of its atmosphere.
The entire lower edge of the platform is 4 inches from the
floor, to allow full circulation of air under it.

In order that a strong up-current may be constantly ensured
in the foul-air shafts, other coils are placed in them, and the
entrance and boiler flues are also made to pass through the
foul-air shafts, of course without any communication. The
foul-air or extraction shafts should never be placed in the
outer wall if possible, owing to the defective up-current from
loss of heat. If such an arrangement cannot be avoided, the
loss of heat maybe diminished by a double wall and air space.


1 3 5 6 7 8 9 10

Online LibraryArthur NewsholmeSchool hygiene: or, The laws of health in relation to school life → online text (page 3 of 10)