The air and ventilation of subways

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CHAPTER I Evolution of the Modern Subway : Pagb

New London tubes 3

Paris subways 4

Berlin subways 4

Other European subways 5

American subways . 5

Underground adjuncts of subways 7

Effects of subways on congestion of population ... 9

The Bearing of Subways on Health 11

CHAPTER II The Atmosphere of the Open Country

The reserve supply of pure air 13

Gases of the normal atmosphere 14

Water vapor 18

Optimum conditions of moisture, cold and heat .... 19

Dust 20

Forms of life 22

The Air of Towns and Cities:

Air of London, Paris and New York 24

Unwholesome gases . 26

Composition of city dusts 28

Effects of atmospheric impurities in cities 29

Frequency of disease due to infected air 32

V

VI

CONTENTS

The Air of Confined Spaces: P^ob

gomposmon of respired air 32

Cause of unpleasant odors 34

Amount of carbon dioxide produced by human bfings . 35

Value of analyses 36

Heat produced by human beings 37

Moisture probuced by human beings 38

Amount of space required for decency, comfort and

SAFETY . . 39

Supply of air required 41

The demand for better conditions 41

Standards of purity for the air of subways 42

Calculation of fresh air requirements 44

Effects of bad ventilation 45

Chapter III Methods Of Ve5tilati50 Subways

Fundamental Considerations :

Differences in the problems of ventilating subways,

tunnels and mines 48

Necessity for skill in design and maintenance .... 49

Physical principles involved 49

Mechanical principles 50

Physical principles involved in subway heating and

cooling 53

Practical Systems in Use :

The exhaust and plenum principles 54

Action of fans applied at various points 55

Action of pans applied at one end of a subway .... 61

Natural ventilation 62

The piston action of trains 64

CHAPTER IV Metropolitan and District of London

Work of an official investigating committee 72

Operating conditions 73

Company's experiments with ventilation 74

Natural ventilation 75

CONTENTS Vll

Metropolitan and District of London: — continued Page

Condition op the air 75

Methods op ventilation studied by the committee ... 77

Final conclusions of the committee 79

The Parallel Tubes of the Central London Railway :

Construction 80

Method of ventilation 80

Chemical conditions 81

Bacteriological conditions 82

City and South London Railway 83

The Metropolitan Railway of Paris 84

Results of an Inspection of European Subways in 1907:

Sensible condition op the air 90

Roadbeds 92

Odor 93

Dust 96

CHAPTER V Scope of the Investigation 100

Essentials of Construction and Operation at the Time of the Investigation :

Steel and concrete in the subway 103

Part of subway in operation 104

Section chosen for closest observation 104

Nature op the travel 106

Sanitary features of construction 109

Provisions FOR VENTILATION 113

Phenomena of ventilation 115

Temperature and Humidity:

Methods employed 123

Results of temperature and humidity observations . . 129

Vlu CONTENTS

CHAPTER VI THE AIR OF THE NEW YORK SUBWAY (Continued) Chemical Condition of the Air: p^^_

Methods op analyses 139

Carbon dioxide results 147

Oxygen results 154

Bacterial Condition of the Air:

Quantitative methods op analysis 155

Additional bacterial work 161

Results ; 164

Methods op investigation 172

Results op investigating the causes 172

Dust:

Methods op examination 178

Ultimate number op dust particles 181

Results 183

Chapter VII Health Of New York Subway Employees

Plan of the Investigation 195

The Condition of the Air:

Physical and chemical composition of the dust .... 197

Bacterial composition op the air and dust 198

Sources op the iron dust 198

Weight op dust in air 199

Weight op dust inhaled 200

The dangers op the dust 201

Injurious properties op subway dust 201

Contributing pactors 202

Natural depenses against dust 203

Condition op throats and lungs op city dwellers . . . 204

Disease due to iron dust 205

Description of the Subway Employees:

Physical appearance op the men 207

Regular duties op the men 208

Medical history bepore and apter entering subway

employment 209

CONTENTS IX

Page Results of the Physical Examinations of the Employees:

Examination of principal organs and byes 210

Examination op the upper air passages 210

Examination of the lungs 211

Results of Analyses of Sputum, Urine and Sweat: 212

Results of the Autopsies 213

Possible Causes and Consequences of the Pleurisy Found:

Pleurisy among the subway employees 218

Normal amount of pleurisy among city dwellers . . . 220

Cause of the pleurisy 225

Recommendations 228

THE AIR AND VENTILATION OF

SUBWAYS

CHAPTER I SUBWAYS Ain> THE PUBLIC HEALTH

The development of subways as a means of facilitating the movement of people from point to point within the limits of a single city forms an interesting chapter in the history of modem transportation. Placed in the last few years upon a successful basis as a result of operating and structural devices not before practicable, nearly all the largest cities now possess one or more subways and scores of smaller places are planning them.

In the construction of subway systems, London, the most populous city, has at all times held first rank. Not only were the first subways built there, but, in face of repeated failure, subway construction was persisted in in London until it became a popular success. To-day there are more types of subways in London, and a greater aggregate mileage of them, than can be found in any other city.

EVOLUTION OF THE MODERN SUBWAY

The first important tunnel built solely for the transportation of passengers from one part of a city to another ran under the Thames in London about two miles below London Bridge. The object, as in several other river tunnels which were built in early times, was merely to afford means of passing from one shore to another and not

to connect with any surface transportation system.

This first subway was begun in 1824 and was opened in 1843. The cost was about $2,340,000. It was intended for horse-propelled vehicles as well as foot passengers. It was 1200 feet long, 14 feet wide and 16 feet 4 inches high. There were, in fact, two parallel tunnels of these dimensions, running side by side, separated by a masonry pier 4 feet thick. The undertaking paid so poorly that the receipts were scarcely sufficient to meet the cost of repairs. This road now forms part of the East London Railway having been purchased in 1865 for less than one-half the original cost.

The first subway to be pro\dded with its own vehicles for transporting passengers was constructed in 1863 under the Thames near the Tower Bridge. This tunnel was a circular iron tube composed of segments bolted together and was 7 feet in diameter and 1350 feet long. As in modem tube railways, passengers were taken up and down in elevators through shafts. These were 10 feet in diameter and 60 feet deep. Transit from one end of the tunnel to the other was accomplished on a single track by means of cars hauled. by wire ropes. This subway was closed to passengers in 1897 and is now used for a gas main.

In view of the failure of these two tunnels to meet popular favor, it is interesting to note the complete success of the Blackwall tunnel which runs under the Thames about six miles below London Bridge. It was opened in 1897 and is used by passengers and pedestrians. The total length is 6210 feet, of which 1740 feet are approaches. This tunnel is next to the largest shield-driven tube in existence, being 27 feet outside diameter. The inside is lined with light-colored glazed tiles and is paved with granite blocks on the inclines and with asphalt elsewhere. It is well lighted and the air is agreeable, ventilation taking place through large shafts on the two opposite shores.

The first extensive underground railway which can properly be termed a system was the Metropolitan and District of London. Its object was to carry the public more expeditiously and comfortably from place to place within the city than could be accompUshed on the surface. This road was opened from Paddington, the terminus of the Great Western Railway, to Farringdon Street in the business district, in 1863. Extensions were numerous up to 1884, at which time the system had been so developed as to form a complete circle around the inner portions of the city.

To-day, the Metropolitan is almost the only example in London of a shallow railroad subway, that is, one built near the surface of the ground and reached by stairways. All the rest, and there are six more, have been built in the London clay at depths which vary from 40 to 150 feet below the surface.

The pioneer deep tube subway imder city streets was the City and South London and was opened for traffic in 1890. It is about three miles long and, Uke practically all deeplying roads, is composed of two metal-lined tubes running side by side. This road has been very successful, carrying in the first year of operation about 2,400,000 passengers. It was the first important city subway to be operated by electricity. The original intention was to use an endless cable for moving the trains.

New London tubes. By far the best known and one of the most profitable deep subways is the Central London which was opened in 1900. After this came the Great Northern and City, opened in 1904, the Waterloo and City, the Baker Street and Waterloo, the Great Northern, Piccadilly and Brompton and the Charing Cross, Euston and Hampstead.

The average internal diameter of these deep tubes is 11 feet 6 inches. They occasionally follow steep grades and curve about continually. The different roads are frequently connected at stations by passageways for foot passengers, i^

Paris subways. Following the example of London, the city of Paris, in 1898, laid out an elaborate plan for subways. The road was built to reUeve the lack of public transportation facihties in Paris itself and to develop poorly populated and distant quarters in the suburbs. It was at first thought that only a part of the whole plan would be carried out, but the success which followed the opening of the road was so great that it was at once decided to finish the entire system. Passengers were first carried in 1901.

Unlike most of the London roads, the Paris subways belong to the type which runs close beneath the surface of the ground, are built of masonry, have two or more tracks and are reached by stairways from the streets. Since the opening of the Paris system, extensive construction has been in progress both by the city and by private capital, so that, at the present time, Paris has the second greatest aggregate underground railroad mileage of any city.

Berlin subways. The city of Berlin is provided with a combined subway and elevated system which was opened for traffic in 1902. It is one of three roads which run partly overhead and extends through the central part of the city from east to west. The tunnels were constructed under the streets, the top sometimes approaching to within 2 feet of the surface. The subway system was considerably extended in 1907.

Other European subways. The city of Budapest has an electric underground railway about two miles in length opened in 1896. It is a double-tracked, overhead trolley system built near the surface of the ground and in design resembles the subways of Boston, New York and Philadelphia.

Glasgow has a subway six miles long partly of the deep, and partly of the shallow, type.

Many other important subways now exist in Europe. Some belong to the period of earliest construction, while others are of a newer type. Nearly all are operated by electricity.

m

American subways. Aside from the terminal connections of trunk line railroads, the first underground city railroad in America was built in Boston and was begun in 1895. This road runs under the business part of the city with a branch under the harbor and accommodates several lines of trolley cars as well as trains of the Boston Elevated System. It is not provided with its own cars but is used by outside lines which otherwise would run on the surface and interfere with street traffic. It was estimated that at least 50,000,000 passengers used the original subway during the first twelve months after its completion and its use has apparently increased since then by over 60 per cent.

The New York subway was opened in 1904. It was considered to be the most perfect example of subway construction yet afforded and was expected to play an important part in relieving the congestion which is rapidly growing at the southern end of Manhattan Island. It is, like most subways, chiefly of the shallow type, A description of its principal features will be found beyond. (See Figsi 1 and 2.)

An account of the plans for the development of underground and under-water transportation m New York which have followed the opening of the first subway would pass the limits of space of this volume. They include roads under the Hudson river and East river and extensions of the original line aggregating many miles in length.

The history of the construction of city subways shows that although underground roads were built over fifty years ago, it was not until electric traction became practicable, bringing with it the possibility of good air, that city subways on a large scale were successful. It is interesting to note that the key to success depended largely upon the question of sanitation. Subways could not be made even tolerably agreeable so long as it was necessary to light them by oil and propel the cars by means of coal-bummg locomotives. To such conditions no public could be expected to become indifferent. On this point the history of the Metropolitan of London is conclusive.

Underground adjuncts of subways. In the rapid growth of subways which has here been outlined, the construction has not been confined to the simple form of structure originally adopted. Both with respect to main lines and auxiliary passages, developments have been made which are of considerable interest when viewed from a sanitary standpoint.

The New York subway differs from most foreign roads in having four tracks instead of one or two, in being provided with express as well as local services, in having underground stations with elaborate toilet room facilities and in having numerous underground connections with office buildings and shops. These lateral connections sometimes run for considerable distances through the basements of skyscraper office buildings, hotels and shops. The passages often accommodate barber shops, restaurants, news stands, fruit and candy stands, soda fountains and flower booths.

The lateral underground passages of the deep London tubes are often long and devious, but they are used only by pedestrians and do not contain shops. On the station platforms of practically all subways are automatic vending and weighing machines. The articles sold are innumerable in variety.

It is needless to remark that in all these lateral subterranean passages the sun never penetrates and it is always night. Fresh air enters only through doors and through elevator shafts. The air is usually cool. The volumes of air passing are often very large. Where candy, fruit and other food is sold it is usually quite unprotected from the dust and air.

Effects of subways on congestion of population. It would be interesting, if space permitted, to discuss the effect on congestion of population which the construction of underground railroads for urban intercommunication has produced. It would be seen that the ultimate eflfect has been quite opposite to that sometimes intended, for, instead of relieving congestion, they have increased it. If the subways have given new outlets from the overcrowded sections of cities to the more sparsely settled ones, they have also provided means by which the overcrowded places can be more rapidly reached than formerly, with the result that the worst places have been still further congested. This added congestion means serious inconvenience and possibly injury to the public health.

Some of the inconvenience which results from congestion is but too evident to every person who visits the business districts of a great city during business hours. The streets are so crowded that pedestrians overflow from the sidewalks upon the carriageways and there is so little room on the carriagewa3rs that vehicles are able to thread their way only with difficulty and at greatly reduced speed.

Nor does the effect of this crowding bear only on the mere convenience of the pubUc. It interferes seriously with the conduct of trade. This means loss of money. Sir John Wolfe-Barrv * and Mr. R. G. H. Davison have calculated that the loss of time experienced through the congested condition of London streets affects persons whose annual aggregate earning capacity is £173,291,000 and of vehicles whose time is valued at £16,562,000 annually. If the loss of time to each one of these wage earners is only five minutes in each day of eight hours, the total loss in money which would be produced in a year would be £1,898,534. It is not improbable that the actual loss is much greater.

Careful studies in America and Europe as to the causes and remedies for overcrowded streets have been carried on by a Royal Commission on London Traffic, and an advisory board composed of Sir John Wolfe-Barry, Sir Benjamin Baker and William Barclay Parsons, engineers of international reputation, have shown in a report to this commission that by bringing more and more people from the immediate suburbs, the development of city railways has increased congestion to such a point that it is now necessary to widen streets, plan for proper sub-structures beneath the streets and regulate the heights of buildings if more serious consequences to the commercial welfare of the city are to be avoided.

* Memorandum by Sir John Wolfe-Barry, K.C.B., and Mr. R. G. H. Davison, M. Inst. C. E. in Appendix to Report of Advisory Board of Engineers to Royal Commission on London Traffic, pp. 675-6, Vol. 8.

SUBWAYS AND THE PUBLIC HEALTH 11 THE BEARING OF SUBWAYS ON HEALTH

A study of all the effects of subway conditions on public health would form an extremely difficult inquiry and obviously can only be dealt with here in a most general manner.

Vital statistics are not available to show the state of health of persons who use subwasrs as compared with those who do not, nor are facts at hand to indicate diflferences in public health which can, with certainty, be ascribed to underground railways.

For practical purposes, it is probably safe to assume as a groundwork of inquiry that if subways produce evil eflfects upon the health of the traveling public, these eflfects are due to overcrowding or some harmful quality of the subway ain

Chapter II The Atmosphere Of The Open Country

So far as known, there is only one constituent of the atmosphere which is directly useful to living beings and this is oxygen. The other gases are not immediately necessary, although they perform many indispensable fimctions in the economy of nature.

The essential act of respiration is an absorption of oxygen and a production of catbon dioxide. It is natural to think of this exchange as one which takes place only in the lungs, but it is really common to all the myriad cells of the body. The lungs act simply as central exchange depots; the distant cells are the real laboratories.

The principal gases of the atmosphere are present in a mechanical mixture and not in chemical combination with one another. A portion of the oxygen may be abstracted without affecting the other constituents and other gases may be added without affecting the oxygen. Oxygen has always the same properties whether it is freshly prepared or not. Fresh air is simply air which is uncontaminated.

Were it not that the atmosphere is being constantly and vigorously agitated, and an incessant mixture taking place through the operation of the physical principles known as diffusion and convection and the action of winds and lesser air currents, human existence in cities and houses would be impossible and life on any part of the earth's surface would cease to exist.

The reserve supply of pure air. Inasmuch as heavy draughts are made upon the supply of oxygen by Uving creatures and by the combustion of fuel, to say nothing of the impurities produced, it is evident that the supply in inhabited places must be continuously renewed. The open country, the sea and the upper atmosphere are the great reservoirs of pure air.

How great is this reserve is not certain, for the height of the atmosphere above the earth is not known with exactness. It was formerly supposed that it extended to a depth of about fifty miles, but observations of meteors, which are believed to grow luminous through heat generated by friction with the air of the earth, have led to the belief that the atmosphere extends even to a greater height than one hundred miles.

It has often been suggested that the oxygen of the atmosphere might, in time, become exhausted, and many ingenious calculations have been made with respect to this subject. For example, it has been calculated by Remsen that, assuming the population of the earth to be 1000 million human beings, the quantity of oxygen used in respiration in a year amounts to about ^,^7rV,7r7rTr part of the supply. Supposing that the quantity of oxygen required for other purposes is nine times this, then the total amount used up in a year would be only ^ir7r,Tnr7 of the whole supply. In eighteen hundred years the decrease in the amount would be only 0.1 per cent.

Whether there has been a decrease in the past it is not possible to say. From many considerations it appears probable that the quantity of oxygen in the air will never become appreciably reduced.

Gases of the normal atmosphere. It was supposed until a few years ago that all the essential facts concerning the identity of the gases of the atmosphere were known, but a number of new gases have recently been discovered. The proportion of these new elements is very small and they appear to have no influence upon health.

In the open coimtry, upon the ocean and at all elevations, the proportion of the leading constituents of unpolluted atmosphere are nearly constant. When decided differences have been reported it is probable that they have been due more to errors inseparable from the analytical technique than to real inequalities.

Still, inasmuch as small differences frequently do occur in cities and other occupied places, it is desirable in studying a problem of ventilation to determine the condition of the surrounding outside atmosphere at the time and place in question as well as the atmosphere of the enclosed space under consideration.

To get a general idea of the principal constituents ofthe free atmosphere under average conditions, we may accept the figures adopted in a recent English Government inquiry concerning the ventilation of workshops.*

According to this authority, pure atmospheric air, free from aqueous vapor, may be taken to have the following composition by volume.

Oxygen 20.94

Nitrogen 78.9

Argon 0.94

Carbonic Acid 0.03

100.00

* Report of a Parliamentary Committee on the Ventilation of Factories and Workshops, London, 1902, p. 93.

Included in this list, although not specifically mentioned, are gases of decomposition, principally ammonia and sulphur compounds, which, with varymg proportions, are probably always present in minute amount.

According to Ramsay,^ the rare gases mentioned in the foregoing table and recently separated from nitrogen are present to the following extent; Helium, 1 part in 245,300 volumes of air; neon, 1 part in 80,800; argon, 1 part in 106.8; krypton, 1 part in 20,000,000; xenon, 1 part in 170,000,000.

Many authorities doubt whether that active form of oxygen called ozone actually exists in the atmosphere, notwithstanding the popular belief in its presence and the fact that some investigators have made systematic determinations of what they have thought was ozone for many years. On the other hand, Ramsay is of opinion that peroxide of hydrogen, an active gas resembling ozone in some of its properties, is generally present in very small quantity. The presence of ozone or peroxide of hydrogen is not without sanitary significance in a sample of air, for, owing to their energetic oxidizing properties, the presence of either gas may be taken to indicate the absence of organic matters.

Odors. Contrary to general belief, pure air is odorless, colorless and tasteless. Many of the odors noticed at the seaside and in the forest are due to substances thrown off in the growth and decay of v^etation and are by no means directly beneficial to health.

Odors are nearly alwa3rs due to gases and not to solid particles, as is popularly supposed. The impression of freshness noticeable in the country and after showers is

^ Gases of the Atmosphere, London, 1905, p. 257.

more often due to absence of odor than to the presence of it. Even the dirty air of streets may seem sweet and fresh on emerging from a badly ventilated enclosure.

The sense of smell differs greatly among different persons and under different circumstances. Warmth and moisture favor the detection of odors.

To be accurate, what we call smell is a mental effect due to the excitement of the olfactory nerve when suitable substances come in contact with the external cells to which this nerve is attached in the more remote parts of the nasal cavity. Odors can be, and are, continually smelled through the mouth as well as through the nose, many so-called flavors used in the preparation of food being, in reality, substances producing odors and not tastes. Sensations of taste originate in the tongue and are restricted to such impressions as those of sweetness and sourness, bitterness and salinity.

The first moment of contact gives the most acute sensation of smell; this sense rapidly becomes blunt after continued exposure. To most persons a subway, which at first seems to have an extremely strong and unpleasant odor, has no odor at all after five minutes or so. This acquired dullness toward one odor may not affect the keenness of perception for others. It is remarkable how soon persons get used to the odors which in one way or another they themselves produce and object to much less pronounced odors from other sources.

A partial or total abolition of the sense of smell may occur as a result of a catarrhal condition or the action of injurious gases. It is not uncommon for persons who live in cities to become very defective in the acuteness of this sense.

Many gases are detectable by smell when in extremely dilute form. Then the odor of musk can be detected for many years without any sensible loss in weight.

It is doubtless chiefly in their power of suggestion that certain odors of the atmosphere appear to be beneficial. And we may say on the converse side of this proposition that odors which are unpleasant are probably harmful only because of the unpleasant mental impressions which. they create. No other sense is capable of calling up such vivid mental pictures as does the sense of smell. Probably no sense is so capable of leading one astray.

Carbon dioxide. Aside from oxygen, the two gases which are of greatest interest in studies of ventilation are carbon dioxide and water vapor. No other normal gases of the atmosphere vary so much as do these two and none, under ordinary circumstances, has such an effect upon comfort.

The peculiar interest which attaches to carbon dioxide lies in the fact that it is a convenient measure of the extent to which air is vitiated by breathing, by lights and by fires. It is a product of respiration and of the combustion of fuel and at the same time varies little in uncontaminated air. There appears to be little difference between the amount present in pure country air, whether in forests or over the ocean.

From accurate anal3^es made in France by Reiset ^ who used samples of air measuring 525 liters each, 2.96 volumes of carbon dioxide per 10,000 volumes of air appears to be close to the normal for the country. Angus Smith reported that the air among the Scotch hills contained 3.36; J. S.

* Annales de Chimie et de Physique, Vol. 26, 1882, p. 198.

and E. S. Haldane/ 3.0, and G. F. Armstrong, 3.13 for the country air of Scotland. Three parts may be accepted as sufficiently correct for most purposes.

Water vapor. Water vapor, not to be confounded with moisture in visible form to which the term vapor is so often applied, is always present in a normal atmosphere.

It is usual to refer to the presence of water vapor as humidity and to the ratio of the quantity present to the maximum quantity which could be present at a given temperature as the precentage of relative humidity. Close to the ocean the relative himiidity is generally in the neighborhood of 90 per cent, but in very dry places it may go below 10 per cent.

When there is present all the w:ater vapor which is possible, the air is commonly said to be saturated, a phrase which some meteorologists object to on the ground of literal inaccuracy. It would be more scientific to say that the space under consideration is saturated, for if any additional evaporation should take place into it some of the vapor already existing would have to return to the liquid state. But it is customary in this, as in some other directions, to employ the term which is generally understood rather than to insist upon excessive accuracy. Saturation of the air is a sufficiently correct expression for popular purposes.

One of the most important facts to remember concerning the existence of water vapor in the atmosphere is that the greatest amount possible varies decidedly with the temperature. While at degrees Fahrenheit, the greatest possible weight of a cubic foot of vapor is 0.54 grain, or 35 milligrams,