_VENTILATION_
The average individual breathes in and out about eighteen times a
minute, taking into his lungs the air surrounding him at the time and
expelling air so modified as to contain large amounts of carbonic acid,
organic vapor, and other waste products of the lungs. The volume of air
taken in is about the same quantity as that expelled and amounts to
eighteen cubic feet per hour. Fortunately, the air expired at a breath
is at once rapidly diffused throughout the surrounding atmosphere, so
that, even if no fresh air were introduced, the second breath inhaled
would not be very different from the first. But after a certain length
of time the air becomes so saturated with the waste products of the
lungs that it is no longer fit to breathe, and it is evident that in
order to keep the air in a room so that it can be taken into the lungs
with any reasonable degree of comfort, there must be a continual supply
of fresh air admitted with a proper provision for discharging polluted
air. If this is not done, there is, so far as the lungs are concerned, a
process established similar to that which is occasionally found when a
village takes its water-supply from a pond and discharges its sewage
into the same pond.
Not long ago, the writer found in the Adirondacks a hotel built on the
side of a small lake which pumped its water-supply from the lake, and
discharged its sewage into the same lake only a few feet away from the
water intake. That the hotel had a reputation of being unhealthy, and
that it had difficulty in filling its guest rooms, is not to be wondered
at, and yet individuals will treat their lungs exactly as the hotel
treated its patrons.
_Effects of bad air._
In order to establish a proper relation between the amount of impurities
diffused through the air and the physiological effect on individuals
breathing that air, certain observations have been noted and certain
experiments have been made which prove without question the injurious
effect of vitiated air.
Professor Jacob, late Professor of Pathology, Yorkshire College, Leeds,
gives the following example on a large scale, to show the results of
insufficient ventilation: "A great politician was expected to make an
important speech. As there was no room of sufficient dimensions
available in the town, a large courtyard, surrounded with buildings, was
temporarily roofed over, some space being left under the eaves for
ventilation. Long before the appointed time several thousand people
assembled, and in due course the meeting began; but before the speaker
got well into his subject, there arose from the vast multitude a cry for
air, numbers of people were fainting, and every one felt oppressed and
well-nigh stifled. It was only after some active persons had climbed on
the roof and forcibly torn off the boards for a space about twenty feet
square that the business of the meeting could be resumed."
Remembering that the process of breathing is for the purpose of
supplying oxygen to the blood and that the absorption of oxygen in the
lungs is the same process which goes on when a candle burns, the
following experiments were made by Professor King of the University of
Wisconsin, to show the effect of expired air on a candle flame. He took
a two-quart mason jar and lowered a lighted candle to the bottom, noting
that the candle burned with scarcely diminished intensity. Through a
rubber tube, he breathed gently into the bottom of the jar, with the
result that the candle gradually had a reduced flame and was finally
extinguished. He observed also that if the candle were raised as the
flame showed signs of going out, the brilliancy of the flame was
restored, while lowering the candle tended to extinguish the flame. Even
when the candle was raised to the top of the jar, the flame was
extinguished after sufficient air had been breathed into the jar.
Clearly, then, he argued, air once breathed is not suitable for
respiration, unless much diluted with pure air. He argued from this that
if a candle using oxygen for combustion could not burn in expired air,
therefore an individual using oxygen for the renewal of the blood could
not be properly supplied in a room partially saturated with the expired
products of the lungs.
Professor King also experimented with a candle burning in a jar on which
the cover had been placed, and found that the candle was extinguished in
thirty seconds, and he argued that if a candle was thus extinguished on
account of the carbonic acid given off, so a person shut up in an
air-tight chamber would similarly be extinguished in the course of
time.
To prove that expired air is poisonous to animal life, Professor King
experimented on a hen, placing the same in a cylindrical metal air-tight
chamber eighteen inches in diameter and twenty inches deep. The hen
became severely distressed for want of ventilation and died at the end
of four hours and seventeen minutes.
In the Wisconsin Agricultural Experimental Station, an experiment was
conducted for fourteen days on the effect of ample and deficient
ventilation on a herd of cows. The stable was chiefly underground and
had two large ventilators which could be opened or closed at will. The
food eaten, the water drunk, the milk produced, and weight of the cows
were recorded each day. For a part of the time the cows were kept
continuously in the stable with all openings closed, and then the
ventilators were opened, the alternate conditions being repeated at
intervals of four days. The amount of food consumed was practically the
same under both conditions. The quantity of milk given was greater with
good ventilation. The chief difference was in the amount of water
consumed, since with the insufficient ventilation the cows drank on the
average 11.4 pounds more water each, daily, and yet lost in weight 10.7
pounds at the end of each two-day period. Examination of the animals
themselves also showed that a rash had developed on their bodies which
could be felt by the hand and which was apparently very irritating,
since it was so rubbed by the animals as to cause the surface to bleed.
The evident teaching of the experiment is that under conditions of poor
ventilation, it was impossible for the lungs to remove waste products to
as great an extent as usual, and, therefore, the demand for additional
water was felt in order to stimulate greater action on the part of the
kidneys to care for these waste products. That this was not a successful
substitute was shown by the loss of weight in the animals, and by the
irritation of the skin which evidently was trying to eliminate some of
the remaining impurities through its surface.
_Modifying circumstances._
Fortunately for mankind, it has not been customary, nor even possible,
to build dwellings or stables approaching the air-tightness of a fruit
jar. Air has great power of penetration, particularly when in motion,
and a wind will blow air through wooden walls, and even through brick
walls, in considerable quantity. It is practically impossible to build
window casings and door frames so that cracks do not exist, through
which air may find its way. When, however, in the wintertime, storm
windows have been put on, or when, as occasionally happens, to keep out
drafts, strips of paper are pasted carefully around all window casings,
or when rubber weather strips are nailed tight against the windows and
doors, conditions are obtained which resemble the mason fruit jar, and
under those conditions, a person living continuously in such a room is
experimenting on himself as Professor King did with the candle.
Another reason why it is difficult to make a room an air-tight chamber
is that if a stove or fire-place be in the room, a strong suction is
produced through the flame, and such suction requires the entrance of
outside air. It is a common experience that a fire-place in a room
otherwise tight will refuse to draw and will smoke persistently until a
door or window is opened, when, a supply of air being provided, the fire
is made bright and active.
Fortunately, the vitiation of the air in a room is never so severe as
that in an experimental chamber, and there are few examples which can be
cited of men or women dying from lack of ventilation in an ordinary
room. But the serious aspect of inadequate ventilation is not that it
actually induces death, but that it decreases the powers and activities
of the various organs of the body; that it interferes with their normal
processes, that it loads up in the body an accumulation of organic
matter which is normally oxidized by fresh air and which, if not
oxidized, obstructs the activities of other organs of the body.
_Danger of polluted air._
Unfortunately, it is not possible to detect by the physical senses that
point at which the human organism suffers from insufficient ventilation.
Some years ago, Dr. Angus Smith built an air-tight chamber or box in
which he allowed himself to be shut up for various lengths of time in
order to analyze his own sensations on breathing vitiated air. He found
that, far from being disagreeable, the sensation was pleasurable, and he
says, "There was unusual delight in the mere act of breathing," although
he had remained in the chamber nearly two hours. On another occasion he
stayed in more than two hours without apparent discomfort, although
after opening the door, persons entering from the outside found the
atmosphere intolerable. He placed candles in the box, which were
extinguished in a hundred and fifty minutes, and a young lady, who was
interested in the experiment, going into the box as the candles went
out, breathed it for five minutes easily; she then became white, and
could not come out without help.
Nor is it possible to conclude from the experiments and observations
cited that the body remains indifferent to polluted air until the latter
has reached a certain definite saturated condition. There can be little
doubt but that a degree of pollution far short of that necessary to
produce death has a weakening effect on the human organism, and that by
means of the increased functional activity of other organs doing work
intended for the lungs the resistance to disease is much impaired. Life
is a continual struggle of the bodily tissues against the attacks of the
micro-organisms and their tendencies to destroy life; hence inadequate
ventilation or any other condition which interferes with the normal
action of the organs of the body causes weakness and affords opportunity
for the attack of some disease-producing germ. It stands to reason that
an individual whose lung tissues have become soft and incapacitated must
be more liable to succumb to disease than another whose lung capacity is
large and whose blood has been continually and sufficiently oxygenated.
Perhaps no more impressive proof of this is seen than in the ravages of
consumption, which is so prone to attack those whose vitality is
diminished by living in unhealthy and unventilated cellars or in crowded
tenements. Statistics are very definite on the subject of tuberculosis
among Indians, who rarely suffer from the disease when living in tents
or on the open prairie, but when they become semi-civilized and crowd
together in houses heated through the winter months by stoves, the germs
of tuberculosis take firm hold, and the deaths from this disease are
greater in proportion to population among this race than anywhere else.
_Effect of change in air._
This discussion illustrates another law of disease which makes the
necessity for ventilation particularly great among rural communities
where for nine months in the year outdoor life is freely enjoyed,
namely, that when either an individual or people are brought under
changed conditions, perhaps not unwholesome to those accustomed to them,
those unaccustomed will suffer severely. So a lack of ventilation during
the winter months in a farmhouse is very serious in its consequences to
those who have had the full enjoyment of fresh air through the rest of
the year.
Reference has already been made (in Chapter 1) to the prevalence of
influenza in rural communities, and it is quite probable that this would
be largely eliminated if the lungs were not deprived of their oxygen as
they are in most houses on the farm.
_Composition of air._
Ordinary air contains about 0.04 per cent of carbon dioxid; that is,
four parts in ten thousand parts of air, the other nine thousand nine
hundred ninety-six being made up of oxygen and nitrogen. Of course, it
is not possible to express any definite value for the amount of carbon
dioxid which is objectionable in air, because, in the first place, it is
not certain that the carbon dioxid in itself is the cause of diminished
vitality due to insufficient ventilation, and, in the next place,
insufficient ventilation affects different people in different ways. But
it is known that in the lungs the life-giving oxygen is changed to
carbon dioxid, and that just as carbon dioxid gas will prevent the
combustion of a candle flame, so carbon dioxid gas will destroy the life
of man.
When a deep well is to be cleaned out, the decomposition of organic
matter in the bottom of the well will have, in all probability, caused
the formation of this same carbon dioxid gas, and it is not uncommon for
a man descending into such a well to be overcome by the gas, which, in
some cases, even causes death. For this reason, it is common to lower
into a well, before it is entered by a man, a candle or lantern, on the
probability that if the lantern can stand it, certainly the man can,
while if the lantern goes out, it is wise to avoid the risk of having a
man's life put out in the same way.
_Organic matter in air._
The stuffy and close feeling perceived in an ill-ventilated room is,
however, due to the organic matter from the lungs, which is expired
along with the carbon dioxid, and some chemists have argued that this
amount of organic vapor ought to be measured instead of the carbon
dioxid.
At the present time there is no simple and direct method of measuring
organic vapor, and because this vapor increases in the atmosphere
proportionately to the carbon dioxid gas, it is much simpler to measure
the latter. Then it is impossible to fix a standard of carbon dioxid
because a person whose lungs are well developed and whose blood is well
oxygenated, or, as we say, one who has good red blood can stand, even if
uncomfortable, a few hours of a bad atmosphere without suffering serious
discomfort, while an anaemic or poor-blooded person would be affected to
a greater degree. It is for this reason that in any house no living
room, especially one heated by a coal stove, should be shut up tight
against fresh air. This is the reason why the women of the family, who
have to breathe the same air over and over all day, are pale and weak
and easily susceptible to disease, while the men, who are out of doors
most of the time, and when indoors are made restless by the bad air,
suffer much less from the ill effects.
Experiments seem to show that when the amount of carbon dioxid in the
air has doubled, that is, when the expired air mixed with the air in the
room has increased the proportion of carbon acid from four parts in ten
thousand to eight parts in ten thousand, that the air is seriously
affected, and that such ventilation ought to be provided that no greater
amount than this could occur. This is such a condition that the room
smells "close" or stuffy to a person coming in from outdoors, indicating
organic emanations as well as an excess of carbonic acid gas. The
question then is: how may this condition be avoided in an ordinary
house, or in an ordinary stable, because the health of the cattle on a
farm, judging at least by the character of the buildings provided, is
quite as important as the health of the farmer's family.
We must take it for granted that no such elaborate schemes are possible
as in public buildings or schools, where fans are provided, either to
force air into the several rooms or else to suck it out. The ventilation
of the house must be more simple and easily adjusted and must depend on
the principle of physics that warm air rises and that if the warm air of
a room is to be removed, air must in some way be supplied to take its
place. The two essentials for ventilation are opportunity for the
ingress and the egress of air--ingress for fresh air and egress for
polluted air.
_Fresh-air inlet._
In the construction, of a dwelling house, special and adequate
preparation for the admission of fresh air is seldom provided, so that
the existing openings must be used for the purpose. This means that in
the summertime an open window will furnish all the fresh air which a
room receives and, when the temperature of the outside air is
approximately that of the living room, such provision is ample and
satisfactory. But in the wintertime, when the outside air is cold, the
average person will prefer to suffer from the bad effects of impure air
rather than admit cold air which may cause an unpleasant draft.
[Illustration: FIG. 14.--Letting in fresh air.]
One of the simplest and best methods of providing an inlet for fresh
air, without at the same time allowing blasts of wind to enter the room,
is to fasten in front of the lower part of the window a board which
shall just fill the window opening; then, raising the lower sash a few
inches will allow fresh air to enter both at the bottom, where the board
is placed, and at the middle of the window between the sashes (see Fig.
14). Persons sitting close by a window thus arranged may feel a draft
even under these conditions, since the cold air thus admitted will sink
at once to the floor and then gradually rise through the room to the
ceiling, but unless one sits too near the window, this is an admirable
method of admitting fresh air.
Another method, where steam or hot-water radiators are placed in the
room, is to connect the outer air, either through the lower part of the
window or through the wall of the room just below the window opening,
with a space back of the radiator, so that the cold air entering will
pass around and through the radiator and so be warmed as it enters.
[Illustration: FIG. 15.--Ventilating device.]
The picture (Fig. 15, after Jacobs) shows the arrangement of the
radiators in one of the buildings of the University of Pennsylvania. A
is the opening in the wall below the window; _D_ is a valve which
regulates the amount of air entering through the opening; _R_ is the
radiator; _B_ is a tin-lined box which surrounds the radiator; _T_ is a
door in front of the box, which when raised allows the air of the room
to be heated and to circulate through the radiator. By adjusting the two
valves _D_ and _T_, air of any desired temperature can usually be
obtained. Figure 16 (after Billings) shows an English device intended
for the same purpose. The valve _D_ in this case operates to admit air,
either through the radiator or to the space between the radiator and the
wall, in order to vary the temperature of the entering air. The valve
_T_ may be open or closed, and its position, together with that of the
valve _F_, determines the proportion of the room air which is reheated.
[Illustration: FIG. 16.--Ventilating device.]
The writer remembers one schoolhouse where these methods were used
successfully, the radiators being placed directly in front of the window
and inclosed at the back, sides, and top, except for an opening to the
outer air through the wall, properly controlled by a damper. In the
writer's own office the radiators are by the side of the window and are
boxed in, the connection being made with the outside air through a
wooden box entering under the radiator. This is an admirable method,
provided the radiator has sufficient surface to warm the fresh air
admitted.
Another excellent arrangement is to provide a narrow screen similar to
that used for protection against flies, but with the screening material
of muslin cloth instead of wire cloth. This muslin will break up the
current of air so completely that no draft is felt by persons sitting
even close to the open window.
_Position of inlet._
The inlet for fresh air, if connecting directly with the outside air,
should not be at the top of the room, since then the inlet would not
serve to admit air, but rather to allow the warm air of the room to
escape, and a burning match would inevitably show a draft outward
instead of inward.
Neither is it desirable to have the fresh-air inlet near the floor of
the room unless the entering air is warm, because cold air admitted will
flow across the floor and remain there, not disturbing the warm upper
layers. The effect then is not to improve the ventilation, but only to
chill the feet of persons sitting in the room. The position of the
window lends itself, therefore, to admission of fresh air, since it is
neither at the top nor at the bottom of the room, but at the level most
suitable for such admission.
_Foul-air outlet._
Very few houses have any provision for the outlet of spent air, and if
ventilation is thought of at all, the only idea usually is to provide,
in part at least, for the admission of air and to make no adequate
arrangement for its egress. Whenever a stove or fire-place is in use,
the mere burning of fuel requires the consumption of air, and in cases
where apparently no air is admitted to the room, insensible ventilation
is at work bringing into the room, through the walls and through cracks
around the doors and windows, the necessary air for combustion.
[Illustration: FIG. 17.--Ventilation by means of coal stove.]
It may be proved by the laws of physics that a coal stove burning freely
in a room causes adequate ventilation; and that only where the dampers
of the stove are closed, so that not merely is the supply of fresh air
diminished, but also the products of combustion are thrown out into the
room, is there danger from lack of ventilation. The stovepipe in this
case furnishes the necessary outlet for the impure air, and the
following suggestion has been made in order to utilize this outlet, even
when the fire is not burning freely or when the damper in the stovepipe
is closed. If the stovepipe from a stove is carried horizontally, as it
usually is, an elbow must be provided to raise the pipe to the stove
hole in the chimney. Then providing a T connection at the point marked
_A_ in Fig. 17 (after Billings), the lower part of the _T_ may be
carried to within a foot of the floor with a damper at the points _B_
and _C_. When the fire is burning freely, the damper at _C_ is closed,
and ventilation is secured through the stove, the damper at _B_ being
open. When the damper at _B_ is closed and the fire checked, then the
damper at _C_ may be opened and the impure air drawn up the chimney from
the level of the floor. This, it is said, is an effective arrangement
for drawing off the polluted air of a room.
[Illustration: FIG. 18.--Coal-stove ventilation.]
Another method is to surround the stove with a sheet-iron casing, as
shown in Fig. 18 (after Billings), the top of the casing having a pipe
leading into the chimney independently from the stovepipe. The casing
becomes warm and heats the room by radiation, just as the stove does,
but if the damper in the flue from the casing be opened partly, a strong
draft along the floor and into this casing will be developed and the
foul air thereby discharged into the chimney. It will be easily
possible, of course, to carry away all the heat from the stove in this
method, and the damper in the flue of the casing must be carefully
regulated to carry away only the desired amount of foul air.
[Illustration: FIG. 19.--Coal-stove ventilation.]
Still another method of using the heat of a stove to secure ventilation
is shown in Fig. 19 (after Billings). Here the stove is surrounded with
a sheet-iron jacket extending from the floor to about six feet above
that level. A pipe is carried from the outside air up through the floor
directly under the stove. By regulating the damper in this pipe the
supply of fresh warmed air entering the room can be regulated. Doors in
the casing must, of course, be provided for the purpose of taking care
of the fire, and of allowing air from the room near the floor to be
heated instead of the outside air.
A most objectionable method of providing an outlet for polluted air from
a room is to have a register in the ceiling with the ostensible purpose
of warming the room above. It was the writer's misfortune once to stay a
week in the country, in a room over the kitchen where this method of
heating was employed, and the odors of cabbage, onions, and codfish
which permeated the upper room, and clung there all night, still remain
as a most unpleasant memory.
_Size of openings for fresh air._
As an indication of the size of the openings needed, it has been said
that in order to provide the necessary air movement, and yet to restrict
the velocity of the moving air so that no objectionable drafts will be
experienced, at least twenty-four square inches sectional area should be
allowed as an inlet for each person, so that one square foot is required
for six persons. This is, perhaps, a theoretical requirement. Certainly,
it is more area than is likely to be obtained in actual ventilation. The
space between two windows, for instance, is about one inch by thirty
inches,--barely enough, according to this rule, for one person, and yet
that opening is sufficient to appreciably improve the quality of the air
in a room occupied by three or four persons.
Taking into account the necessary air required by lamps or gas burners,
the inlet flue should have at least ten square inches area for each
person, so that the ordinary single register should provide the
necessary amount of air for a living room. When, as happens in houses
where a studied effort is made to preserve the health of the
inhabitants, an outlet is cut into the wall and a flue carried up
through the roof, the flue should be preferably near the floor and on
the side of the room opposite the window or inlet. With such an
arrangement (see Fig. 20) the air entering rises at first, but sinks at
once because of the temperature, so that the direction of the air
currents are diagonally across the room from the ceiling to the floor,
thus renewing and changing all the air particles except those directly
over the outlet. Where the air is introduced mechanically, that is,
forced into the room, it is better to have the inlet and outlet on the
same side, so that the entering air is shot in at the top, flowing
across the room, then sinking and coming back, just below the point
where it entered.
[Illustration: FIG. 20.--Outlets into the walls.]
_Ventilation of stables._
All that has been said on the subject of ventilation in houses applies
equally well to the ventilation of stables, and a little book by
Professor King of the University of Wisconsin, entitled "Ventilation,"
deals most thoroughly with the principles and practices of ventilation,
not merely for dwellings but also for stables. Professor King proves by
his experiments that the condition of cattle is much improved and that
the milk-giving qualities are increased by a proper supply of fresh air,
and in the book referred to, he gives a number of examples of the proper
construction to provide adequate ventilation. It is most convincing to
see how unscientific is the old-fashioned underground stable, the sole
idea of which was to conserve the animal heat by crowding together the
cows and by absolutely excluding the outside air. For further details of
his work, its principles and practices, the reader is referred to the
book, which may be obtained from the author at Madison, Wisconsin.
_Cost of ventilation._
To ventilate a house is expensive, and to ventilate a barn requires not
only a certain expenditure of money but also a considerable amount of
judgment. It is evidently cheaper to heat the same air in a room over
and over than to be continually admitting cold fresh air, which will
have to be warmed. This extra cost is, however, not excessive, when the
movement of the air currents is properly controlled. The cost of warming
the air necessary for ventilation for five persons should not be, at the
rate of 1000 cubic feet of air to each person, more than ten cents a day
in zero weather, with coal at five dollars a ton. Enough coal will have
to be burned in addition to compensate for radiation, or, in other
words, it requires a certain amount of coal to keep an empty room warm
in winter without any question of ventilation, and in some badly built
houses this amount is large.
_Relation of heating to ventilation._
It does not follow because much heat is lost in this way that the
ventilation is good, since the heated air may ascend to the ceiling and
there escape without influencing the ventilation. In fact, one of the
first principles of ventilation is that as soon as regular inlets and
outlets are provided, all other openings ought to be rigidly closed.
Then and then only can the warmed pure air be admitted as desired, at
the points intended, and the full value of the heat utilized. Especially
is this control of openings important in ventilating barns. Here each
animal is a natural heater, warming the air by direct contact and by
rapidly breathing in and out large volumes of air which are thereby
changed to a temperature of over ninety degrees Fahrenheit. The air
around their bodies being warmed rises to the ceiling and spreads out to
the two sides and is there gradually cooled and at the same time mixed
with fresh air which enters at the top, so that the cow is constantly
supplied with freshened air. A flue is needed to carry the foul air up
through the roof, and fresh-air inlets in the outer walls on both sides
are required, and with these openings carefully controlled and with no
others interfering, the stable may be well ventilated, as shown in Fig.
21 (after King).
[Illustration: FIG. 21.--Cow-barn ventilation.]
In all cases where ventilation is to be practiced, the walls and ceiling
should not merely be tight in themselves, but they should be double, and
the strictest attention paid to limiting the amount of heat lost by
radiation. All the heat used ought to be concerned in ventilation, and
in that only. To secure air-tight walls and ceiling, the studding and
joists should be boarded in, both on the inside and out, and the space
between should be filled with shavings, straw, dry moss, or any similar
fibrous substance. The outside sheathing must be well laid and must be
water-tight in order that rain shall not penetrate to the inside of the
wall, and the roof must be tight so that the ceiling filling does not
get wet and rot.
The choice, therefore, so far as ventilation of either house or barn
goes, lies between a poorly built, loose-jointed structure without
artificial ventilation and with poor economy in heat, and a well-built,
air-tight structure, with ample ventilating pipes, carefully and
intelligently planned and built. The first is healthy so far as pure air
is concerned, but drafty and uncomfortable. The second is more expensive
to build, but insures lasting health and comfort. Then the choice cannot
but fall on the building which is easy to warm, healthful to live in,
and readily ventilated.