1. Waste of fuel.—It has been found that in a common open English fire, seven-eighths of the heat produced from the fuel ascend the chimney, and are absolutely lost. This lost fuel is thus accounted for. One half of the heat is carried off in the smoke from the burning mass; one quarter is carried off by the current of the warmed air of the room, which is constantly entering the chimney between the fire and the mantel-piece, and mixing with the smoke; lastly, one eighth part of the combustible matter is supposed to form the black and visible part of smoke, in an unburned state. Some writers have even gone so far as to estimate the loss of heat in an open fire at fourteen-fifteenths of the whole. 2. Unequal heating at different distances from the fire.—This forms a remarkable contrast with the uniform temperature in the air of a summer afternoon. In rooms with a strong fire, in very cold weather, it is not uncommon for persons to complain of being “scorched” on one side, and “pierced with cold” on the other; this is particularly the case in large apartments; for as the intensity of radiating heat (like light) is only one-fourth as great at a double distance, the walls of the room farthest from the fire are but little warmed, and, therefore, reflect but little heat to the backs of persons grouped round the fire. 3. Cold draughts.—Air being constantly required to feed the fire, and to supply the chimney-draught, the fresh air which enters by the crevices and defects in the doors, windows, floors, &c., is often felt most injuriously as a cold current. “There is nothing more dangerous to health than to sit near such inlets, as is proved by the rheumatisms, stiff necks, and catarrhs, not to mention more serious diseases, which so frequently follow the exposure. There is an old Spanish proverb, thus translated,
If cold wind reach you through a hole,
Go make your will, and mind your soul,
which is scarcely an exaggeration.” The current of fresh air which enters to feed the fire becomes very remarkable when doors or windows are opened, for the chimney can take much more than it otherwise receives when the doors and windows are shut; and thus the room with its chimney becomes like an open funnel, rapidly discharging its warmed air. 4. Cold to the feet.—The fresh air which enters in any case to supply the fire, being colder and specifically heavier than the general mass already in the room, lies at the bottom of this as a distinct layer or stratum, demonstrable by a thermometer, and forming a dangerous cold-bath for the feet of the inmates, often compelling delicate persons to keep their feet raised out of it by footstools, or to use unusual covering to protect them. 5. Bad ventilation.—Notwithstanding the rapid change of air in the room, perfect ventilation is not effected. The breath of the inmates does not tend towards the chimney, but directly to the ceiling; and as it must therefore again descend to come below the level of the mantel-piece before it can reach the chimney, the same air may be breathed over and over again. In a crowded room, with an open fire, the air is for this reason often highly impure. As another source of impure air in a house, it may be noticed that the demand of the chimneys, if not fully supplied by pure air from about the doors and windows, operates through any other apertures. 6. Smoke and dust.—These are often unavoidable from an open chimney, much affecting the comfort and health of the inhabitants of the house, and destroying the furniture. Householders would make great sacrifices in other respects to be free from the annoyance of smoke. In large mansions, with many fires lighted, if the doors and windows fit closely, and sufficiency of air for so many chimneys cannot therefore enter by them, not only do the unused chimneys become entrances for air, but often the longest and most heated of them in use overpower the shorter and less heated, and cause the shorter chimneys to discharge their smoke into the room. 7. Loss of time.—During the time every morning while the fires are being lighted, the rooms cannot be used; and there are, besides, the annoyances of smell, smoke, dust, and noise, all of which are again renewed if the fire is allowed to go out and to be relighted in the course of the day. 8. Danger to person and to property.—How numerous are the losses of property by carelessness as to fires is well known to all, while the loss frequent but more distressing loss of life too well attests the danger to children and to females thinly clad often consequent on an open fire.
Such are the principal defects which Dr. Arnott enumerates as being inherent in the use of open fires. Many of them have been greatly lessened by improved arrangements; but others are still without an appropriate remedy.
The usual construction of a fire-place is tolerably familiar. In most cases, the vertical or nearly vertical channel for the chimney is inclosed within a casing of brick-work, which projects into the room at one side. The opening for this chimney gradually narrows upwards, until only large enough to admit the poor little climbing-boy whose task it was, until within a recent period, to sweep down the unburnt fuel which our own ill arrangements have wasted; but, happily for humanity and justice, this system is at an end, and machines are now employed for the purpose. A hearth of stone is laid whereon to erect the stove or grate, and this grate is, as we all know, composed mainly of an iron receptacle for the fuel, and of “hobs,” for supporting culinary vessels. We cause fire to be kindled in the grate, and then suppose that all will go on well, without troubling ourselves to inquire whether the arrangements for the supply of cold air, and the exit of warmed air and smoke, are such as are best fitted for those purposes.
Remedies for some of these Defects.
In course of time, as the evils of this plan became one by one known, attempts were made to remedy some of them, and with an approach towards success. In a recent treatise on the subject by Dr. Fyfe, of Edinburgh, various modes are suggested for remedying many of the evils incident to open fire-places. These we must briefly notice.
Sometimes the rooms of a new house are subject to the nuisance of smoky chimneys simply from deficiency of air. The workmanship of the rooms being all good, the joints of the flooring-boards and of the wainscot panels are all true and tight, the more so as the walls, perhaps, not yet thoroughly dry, preserve a dampness in the air of the room, which keeps the wood-work swelled and close. The doors and the sashes, too, work closely and correctly, so that there is no passage left open for the air to enter except the key-hole, and even this is often closed over by a little brass cover. Thus, air being denied admission into the room, there is nothing to feed the fire and to cause a “draught,” and the smoke cannot ascend the chimney. Instances have been known of well-built houses being rendered almost untenantable from this cause, and several hundred pounds being spent in endeavouring to find a remedy. If, on opening the door or window of a smoky room, it be generally found that the smoke disappears, this may be taken as an indication that the close-fitting joints of the wood-work do not admit air enough for the fire when doors and windows are closed. In such a case, the opening of the door or window is a poor attempt at a remedy; for the air proceeds direct to the chimney, and in its way causes cold to the back and feet of those who may be sitting before the fire. Numerous methods have been devised for admitting additional air to the rooms without this inconvenience, among which Dr. Arnott recommends tubes leading directly from the outer air to the fire-place, and provided with what are called “throttle-valves,” for the regulation of the quantity. The following plan has also been recommended as one of the most practicable. As the air in the upper part of a room is warmer than in the lower, it is desirable that the supply should come in that direction, so as to be slightly warmed in its progress towards the fire, and thus produce less chill to those in its immediate vicinity. This may be done by drawing down the upper sash of the window about an inch; or, if not moveable, by cutting such a crevice through its frame; in both which cases, a thin shelf of the length of the opening may be placed to conceal it, sloping upwards, to direct the air horizontally along and near the ceiling. In some houses, the air may be admitted in such a crevice made in the wainscot or cornice near the ceiling, and over the fire-place; this, if practicable, is the better of the two, since the cold air in entering will there meet with the warmest rising air from before the fire, and be soonest tempered by the mixture. Another contrivance is to take out an upper pane of glass in one of the sashes, set it in a tin frame, giving it two springing angular sides, then replacing it, with hinges below, on which it may turn; by drawing in this pane more or less, the quantity of air admitted may be regulated, and its position will naturally direct the admitted air up and along the ceiling. The circular vane or ventilator sometimes fixed in windows admits cold air in a similar manner, when the supply for the room and fire would be otherwise deficient.
The opening or breadth and height of the fire-place, though we may fancy it leads to the diffusion of more heat into the room, is really a cause of loss of fuel, and of smoke. The size of the fire-place opening is often considered in relation to the size of the room, without regard to the principles on which a fire is maintained in a grate; a course about as rational (it has been well observed) as to proportion the step in a staircase to the height of the story, instead of to the convenience of our legs in mounting them. As the chimneys of different rooms are unavoidably of different heights, and as the force of the draught is in proportion to the height of chimney filled with warmed and rarefied air, it is found that the opening for a tall chimney may be larger than for a lower one. If the opening be unnecessarily large, there is room not only for the entrance of fresh air, but also for the exit of smoke driven down by an opposing current from the chimney itself; and the air, too, ascends into the chimney in too cold a state, because the largeness of the opening enables it to enter without passing very close to the fire. The principal evil attending the use of a fire-place having too small an opening, is that the fuel is burned away with unnecessary rapidity. When the opening is found by experience to be so large as to lead to the descent of smoke into the room, the easiest remedy is to place moveable boards or sheets of tin or iron, so as to lower and narrow it gradually. The effect of which, by excluding a part of the colder air from the chimney, is to produce a quicker action, so that the fire begins to roar as if blown by a bellows. “This means is often used to blow the fire instead of bellows, or to cure a smoky chimney, by increasing the draught. What is called a register stove is a kindred contrivance. It has a flap placed in the throat of the chimney, which serves to widen or contract the passage at pleasure. Because the flap is generally opened only enough to allow that air to pass which rises directly from the fire, the chimney receives only very hot air, and therefore acts well. The register stove often cures smoky chimneys; and by preventing the too ready escape of the moderately warmed air of the room, of which so much is wasted by a common fire-place, it also saves fuel.” There does not appear to have been any attempt to determine by experiment the proper opening of the fire-place for a given height of chimney; and, indeed, there are so many disturbing causes, that it would be scarcely possible to determine this with precision. Dr. Franklin, however, proposed to make the fire-place openings in the lower rooms about thirty inches square and eighteen inches deep; those in the upper, eighteen inches square, and not quite so deep; and those in the intermediate rooms, of dimensions between these two extremes.
In some cases, where other matters are properly attended to, inconvenience results from the chimney being too low; as, for instance, in the case of an attic chimney. In this instance the column of heated and rarified air is not high enough to give a rapid ascensive power within the chimney, and thus the smoke cannot be carried up. The best method of cure is to add to the length of chimney, if this can be done, and if the fire be in a low building near the ground, this may perhaps be effected; but in an attic, the means of supporting a lofty chimney would be inefficient. Another recourse is to contract the opening of the fire-place to the smallest available dimensions, so that all the entering air may pass through or close to the fire before entering the chimney, and thus acquire an ascensive power which will counterbalance the shortness of the vertical column. It has been recommended that in some cases there may be three chimneys to one room, so that the united length of the whole may be equal to that of a tall chimney; but it is not easy to conceive how this can be practically effected, nor how the desired result would follow, even if the arrangements were made. In some cases, the chimney of a room is rendered practically shorter by being bent round and made to enter the chimney of another room; since, unless there be a fire in this room also, the warm air from the shorter chimney has often an adverse current to contend against at the junction with the other chimney. This is one reason why every open fire-place should have its own chimney independently of others.