Heating and Ventilating, supplying heat and pure air. Primitive man was satisfied with a fire of sticks built in the open air. Even after the invention of huts and tents the only source of heat was a fire built in the center with an opening above to allow the escape of smoke. The American Indian had no other means of heating. The council fire of the Iroquois was built in the center of a large wigwam. The cliff dwellers of New Mexico built a central fire in the assembly or men's room. Where wood was not to be had they used buffalo "chips" or the dried stalks of weeds. The Eskimo, living in a region where there was no wood, converted a block of soapstone into a rude lamp. A twisted bit of moss served for a wick. The blubber of the seal furnished fat for fuel. The ancients depended entirely on open fires. To avoid the discomfort arising from smoke they devised the plan of charring wood and using charcoal for inside cooking and heating. In art, the aged Roman is represented warming his fingers over a pan of live coals. The open pan, pot, or kettle in which to burn charcoal is called a brazier. Even the wealthiest Roman or Greek had no other plan of heating. The brazier is in universal use in China, Japan, and many parts of India. It is still the chief dependence of the Italian. In fact, it is common in the Mediterranean countries. Many Spanish cities, and even some in South America, cook and heat with the brazier. The fireplace was a distinct advance over the floor fire of the savage. It consisted essentially of a small chamber or cubbyhole at one end of the room, furnished with a chimney for the escape of smoke. In wooden houses the construction of the chimney was of especial concern. It was built necessarily of masonry laid with care to prevent fire from reaching the woodwork. The fireplace is supposed to have been invented in the wooded regions of western Europe. English colonists brought the idea of a fireplace with them to this country. The Virginian house in which Washington passed his boyhood had two large outside fireplaces, one at each end. They were built of limestone and mortar. Very frequently the colonial fireplace was built of bowlders or other loose stones. The chimney was built of sticks laid four square, plastered inside with mud or mortar. These chimneys were a constant source of danger through fire. The fireplace, with a crooked, swinging, iron crane for supporting the housewife's kettle, and andirons for holding fuel in place, are of frequent mention in literature. A very good account of the New England fireplace may be read in Whittier's Snowbound. The fireplace was succeeded by the stove. The stove of continental Europe is still a large structure of masonry, having a small cavity within in which fuel may be burned. Once a fire is started and the interior filled with live coals, the door is closed. It takes hours for a tile stove of this sort to heat up. It cools off slowly, giving out in the meantime a gentle, agreeable heat. Iron stoves were an invention of the eighteenth century. They are too well known to require description. No attempt was made to heat the colonial hall, church, or meeting house. Feeble people carried foot stoves or foot warmers of some description. Public buildings and large residences are now heated chiefly by means of furnances, steam, or hot water. Stated in simple terms, a furnance is merely a large stove in the basement. The firebox is inclosed in a jacket of metal or brick work. An intake pipe conducts fresh air to the space between the firebox and the jacket. The air is heated and is conducted through pipes to the various apartments above. The air does not "rise" through these pipes, but it is driven up by atmospheric pressure from outside acting through the cold air intake. In order that atmospheric pressure may work successfully, air must be allowed to escape from the rooms. A furnace is more or less unmanageable. Furnace heat has a provoking way of pouring up when it is not wanted, and of being sluggish when it is most needed. On a windy day one-half of a building is likely to be cold, while the other half is overheated. A furnace is not expensive to begin with, but it is considered wasteful in operation. Heating by steam has been reduced to a science. Steam is generated in a boiler. It is conducted through an iron pipe to the place where it is required, where the steam is admitted to a mass of short iron pipes, known as a radiator. When the radiators are placed in the apartments that are to be heated, the system is said to be direct. When the radiators are massed in a hot air chamber from which the heat is distributed, the system is said to be indirect. Most engineers prefer to combine the two systems. If the unit of heat be defined as the amount of heat necessary to raise the temperature of a pound of water 1 deg. F., engineers expect a square foot of radiating surface to give off 250 units of heat per hour. By taking into consideration the size of the room and climate, steamfitters know how much radiation to provide. In the cold winter climate of Minnesota the following order may be taken as a guide: Divide the area of the glass windows by 2; the area of the outside wall by 10; and the cubical contents of the room by 200. The sum of the three results in the radiating surface required. Steam distributes itself by reason of its own pressure, of course. Steam gives off an enormous amount of heat in cooling. A pound of steam gives off 536 heat units in the mere change from steam to hot water. Each radiator must be provided with a return or drain pipe through which the water of condensation may drain back to the boiler. In starting a steam plant it is necessary to open a vent in each radiator so that the confined air may escape, or else the steam cannot enter. As soon as the air has been driven out and the radiator has been filled with steam, the vent should be closed. There is no further advantage in allowing a small amount of hissing steam to escape. When the steam plant is closed down for the night the vents should all be open in order that air may enter the radiators as fast as the steam condenses into water. Otherwise the condensing steam forms a vacuum and the steam in the upper part of the boiler drives the water of the boiler up the returns into the radiators. The hot water heating plant is very similar to the steam plant. Both pipes and radiators are filled with water. As the water in the boiler heats, the colder, heavier water in the radiators settles downward, establishing a circulation throughout the entire system. In this way the warm water of the boiler reaches the radiators, warms the rooms, and returns to the boiler to be reheated. An elevated standpipe with an open upper end permits free expansion and prevents an explosion. All in all, hot water supplies the most agreeable and even sort of heat. A foot of radiating surface gives off about 180 units of heat per hour. A greater radiating surface is needed than for steam. A hot water plant costs rather more to begin with, but it can be operated with a lower fire and, up to a certain limit, at less cost. Once a hot water plant is heated up, however, it is like the old continental style of stove; it takes some time to cool it off. Steam can be shut off at once. Boise, Idaho, enjoys a unique system of hot water heating. A deep well furnishes a supply of hot water from subterranean sources. By means of mains and house pipes, a central plant furnishes hot water for heating purposes throughout the entire city. Cities situated near the natural gas belt, as Columbus and Indianapolis, are heated with gas. Hundreds of miles of mains and house pipes introduce the natural gas from oil fields into the public buildings and residences of these cities. The gas is consumed usually in what appear to be small fireplaces. Tongues of flames playing over andirons and castiron logs of the most natural appearance imaginable give apartments the cheerful, open-fire effect of an old-fashioned wood fireplace. Electric heat is used in the arts, as in welding metals and the like. Electricity furnishes a very agreeable domestic heat, but it is too expensive for general use. Engineers consider that an efficient steam or hot water plant converts three-fifths of the possible energy of coal into available heat. The most economical electric plant thus far constructed turns only one-eighth of the energy of coal into available heat. Ventilation is entirely a modern problem. Primitive man, the sport of the winds, may be said to have had too much ventilation. The most expensive buildings of the ancients were built without glass. The windows of the Taj Mahal are closed with marble screens only. The wonderful buildings of Egypt, Greece, and Rome were provided with unclosed openings. In the countries where braziers are used, the climate is mild enough so that the walls of houses are of slight construction. Even the snow igloo of the Eskimo, heated as it is by burning blubber in a stone lamp, is not without ventilation. Air passes through the snow walls, it is said, quite freely. With the introduction of close windows and the construction of practically airtight wooden and masonry buildings, ventilation, especially in the northern part of the world, has become a problem of importance. It is a well established principle of physiology that air once breathed should not be breathed again. While in the lungs it loses a quantity of oxygen and absorbs a quantity of carbon dioxide which renders it positively useless when breathed again. When the hot air chamber of a furnace is fed with pure outdoor air, the air in the rooms heated undergoes a change. Experience shows, however, that furnace ventilation is only partial. On the whole, it is very unsatisfactory. A furnace system of ventilation can be made fairly efficient, however, by providing large foul air ducts. In case of steam heat a radiator located in each duct insures fairly satisfactory ventilation. Too many builders make the foul air escape about one-fourth as large as it ought to be. For churches, schools, lecture halls, and other rooms where many people congregate, the only system found satisfactory is that known as fan ventilation. According to this plan, outdoor air is admitted to a chamber. Here it is heated by steam or hot water. A large fan constructed usually on the principle of a steamship propeller with blades like the sails of a windmill, rotates rapidly in a tube and forces the fresh, warm air through pipes to the various parts of the building. In a complete system, a second fan in the attic draws foul air out of the building. Sometimes the fan is driven by steam pressure from the boiler which supplies heat. It is better, however, to operate the fan by means of an independent gasoline engine or dynamo. Such a system can be depended upon to furnish pure air in all kinds of weather. Engineers lay down the rule that the pure air inlet should have a sectional area, at its smallest point, of not less than one square foot for each fifteen persons. Medical authorities maintain that an adult in good health should be provided with 30 cubic feet of pure air per minute. While this claim may be excessive, it is very evident that, even at increased expense of heating, ventilation should receive attention. It is said that a person can live three weeks without food; three days without water; and three minutes without air. The following pertinent excerpt is taken from a circular of instructions issued by W. W. Walling, chief factory inspector of New York, to his deputies: Ventilation as commonly understood means the removal of foul and the introduction of fresh air, and in many cases it includes the idea of a thorough mixing of pure with impure air, in order that the latter may be diluted to a certain standard. According to Dr. John S. Billings, perfect ventilation means that any and every person in a room takes into his lungs at each respiration, air of the same composition as that surrounding the building, no part of which has recently been in his own lungs or those of his neighbors, or which consists of the products of combustion generated in the building, while at the same time he feels no currents or drafts of air and is perfectly comfortable as regards temperature, being neither too hot nor too cold. . . Expired air contains five per cent less oxygen and a little over four per cent more carbonic acid gas than that which is inhaled. Carbon dioxide, better known as carbonic acid gas, is commonly considered a poisonous gas in the atmosphere, but this is hardly true, as large quantities can be breathed with impunity when pure and mixed with air. It will not support life, and by shutting out the required amount of oxygen it produces asphyxia. We need ventilation because we have to breathe, because every breath uses up and spoils a certain amount of air. A person will drown in one or two minutes, in vitiated air, because good air is kept out of the lungs. Sleeping in a room wherein an open charcoal fire is burning produces the same results as drowning and has been frequently used by those with suicidal bent. In this connection is always cited the famous instance of the Black Hole of Calcutta. This was a room about eighteen feet square, and during the Sepoy Mutiny of 1857, 146 Europeans were incarcerated for a night. Although the room had two small windows, 126 men died during the night, while the survivors lived but a short time. Another case is that of the steamer "Londonderry." which was overtaken by a storm in the Irish Sea. The 200 passengers were ordered below and the hatches battened, when, before their suffering could induce the captain to set them at liberty, seventy-two had died of suffocation. While these are extreme cases, causing almost instant death, impure air produces slow poisoning, and is too frequently the direct cause of consumption and its accompanying diseases, bronchitis, catarrh and pneumonia, while diphtheria, measles and various fevers are promoted by it. The immediate effort of breathing impure air, one experienced by each of us, is a feeling of stupor, inactivity, drowsiness, languor and sometimes headache, vertigo and nausea. Little dependence can be placed on the sense of smell as an agent in detecting foul air, as no other organ is more easily deadened by excessive action than the nose. The oppressive, sickening, ofttimes nauseating odor that greets one upon entering an illy ventilated room is scarcely noticed after a few minutes. Not until the return to the pure air is the foul atmosphere a subject of thought. It has been aptly said that "He who lives in a garden cannot smell a rose, while the woodcutter in the southern forests is insensible to the odor of the magnolia." Stepping into a closed bedroom where a person has slept all night, the smell is often intolerable, while the person who occupied it detects nothing unusual. The peculiar odor common to churches, noticeable upon entry, is forgotten by the time one reaches his pew. It is therefore obvious that the sense of smell is not sufficient to warn us of danger in atmospheric conditions and that other means have to be adopted. The safest and most practicable method is that of measuring the carbon dioxide. While not itself particularly dangerous, carbon dioxide is usually found in very bad company and its presence indicates with much certainty the presence of those really offensive and dangerous gases and impurities which are a menace to life and health. In large factory buildings, heating and ventilating are almost inseparably connected, still there is scarcely a factory in New York where any provision is made for proper ventilation. In order to heat a building with the greatest economy, windows and doors are made as tight and close-fitting as possible consistent with opening, and in many cases the only pure air entering a building is that which finds its way around windows and doors. An old writer said: "When men lived in houses of reeds they had constitutions of oak; when they live in houses of oak, they have constitutions of reeds." Whenever the introduction of sufficient air reduces the temperature of the room to an uncomfortable degree, it is obvious that the ventilation and heating systems must be combined. I believe we are justified in demanding a system that will furnish, in ordinary trades, a minimum of two thousand cubic feet of fresh air per hour for each person, and the removal of the same amount, which supply under no circumstances should fall below 1,500 cubic feet per hour. See FIRE; HEAT; FLINT; MATCHES; COAL; PEAT; STOVE; AIR; WIND; DAMPS; GAS; LUNGS; FAN.