Hot-air Systems.—The advantages of the hot-air system of heating, after the first cost of installation, are that it does not require a supplementary system of ventilation, can be easily cared for, and readily adjusted to changes in temperature. The disad vantages oftenest complained of are the dust and gases that sometimes rise from the register, the difficulty caused by high winds blowing into the cold air boxes, and dryness of the atmos phere caused by delivering the heated air at too high a temperature. But these disadvantages may be overcome by proper construction and installa tion.
To Prevent Dust.—Dust may rind its way either from above or from below into the stream of warm air that rises from the register. To pre vent its rise from below, the outer opening of the cold-air box may be screened with cheese cloth or other thin fabric, and over the seams of the cold-air box and flues may be placed a metal protector with tightly soldered joints. Thus the gases and any foul air that may be in the cellar will be excluded from the draught, and the supply of air coming in from out of doors will be fresh and pure as well as warm. To prevent dust from en tering the flue from above, the regis ters should be closed while sweeping and should be removed each day after sweeping and dusted out of the win dow; one or more thicknesses of cheese cloth or netting should be stretched under the register and across the flue so as to screen the current of air as it rises. Registers set in the wall naturally receive less dust from sweep ing than floor registers do. They also give the warm air a somewhat better circulation.
How to Regulate Hot Air.—Hot air is a misnomer. Overheated air is detrimental to health and also in jurious to woodwork and furniture. The term " warm air " is preferred by most authorities, and the best results are secured by having a relatively large furnace that, by delivering a large quantity of air at a moderate temperature, will heat the house com fortably in the coldest weather. The air should not be delivered at a tem perature greater than 120°, and under no circumstance should the fires be allowed to rage until the fire box is red hot.
To Overcome Dryness.— The dry ness of the atmosphere caused by the warm-air furnace may be overcome by keeping a supply of water in the receptacle usually furnished for that purpose inside the jacket of the fur nace; or by hanging a small tin pail of galvanized iron from a hook below one or more of the registers in the room, so that the current of air there from will receive a small amount of moisture.
Hot Air — To Prevent Waste. — A great saving can be effected by casing the jacket of the furnace mad the hot-air pipes with several thicknesses of asbestos paper to prevent direct radiation in the basement. Heat which would otherwise be wasted may also be utilized by the addition of a hot-water attachment. This combina tion of the hot-air and hot-water sys tems affords, perhaps, the greatest possible economy in fuel. The hot water piping may be used in distrib uting the heat to any parts of the house not equipped with the hot-air system. When possible, the hot-air flues should be so adjusted that the same flue will serve two or more reg isters. Thus, by closing the register in the lower rooms, the heat can be diverted through the same flue to the upper part of the house, with the least possible number of pipes and waste of heat.
The Franklin Stove. — The cele brated device invented in l782 by Benjamin Franklin, and called by him the " Pennsylvania fireplace," is still in some respects the most satisfactory contrivance in existence for heating individual rooms. Oddly enough, in modern stoves of this pattern 4 prin cipal feature of Franklin's invention has been neglected. The Franklin stove had an air chamber behind the grate, communicating with the outer air through a pipe passing beneath the hearth; by this means a current of pure, warm air was admitted to the room for ventilation. If this device could be revived and widely adver tised, there is no doubt that its supe rior advantages would be generally recognized. The modern Franklin stove is similar to an ordinary closed stove except for its open hearth. It combines the cheerful open grate of a fireplace with economy of the heat lost in a fireplace by passing up the chimney. The Franklin stove can be connected by means of stovepipe with an ordinary flue.
Closed Stoves.—Closed stoves burn ing coal, oil, or gas as fuel are, of course, in very general use for heat ing individual apartments. Of these, the coal stove has the very decided advantage that the products of com bustion pass through the stovepipes into the chimney, whereas both gas and oil stoves vitiate the air with car bonic-acid gas and other injurious substances. For this reason, gas logs and gas grates should not be used ex cept immediately under a chimney flue, nor should small gas stoves or oil stoves be used in living rooms or bedchambers without abundant ven tilation.