This section is from the book "The Principles And Practice Of Modern House-Construction", by G. Lister Sutcliffe. Also available from Amazon: How Your House Works: A Visual Guide to Understanding & Maintaining Your Home.
In spite of the care which may have been spent on the sanitary condition of a house, infectious disease may at times be imported into it from outside. Certain considerations then arise which are not outside the scope of this book. W here the case is treated at home, isolation is, of course, imperative, and the choice of a suitable room is of great consequence. It should preferably be at the top of the house for the sake of light and airiness, and because the chances of infecting others are thus lessened: the air-currents in a house pass upwards. It should be reasonably large, well-ventilated, and, if possible, with a light and sunny aspect.It should have a fireplace, for a tire is desirable in any but the most sultry weather, not only to assist ventilation, but for the ready cremation of rags or other material which have received infectious discharges from the throat or nose of the sick person. Ail curtains, carpets, and hangings must, of course, be removed, and only such articles as are absolutely needful should be left in the room, and these should be such as are susceptible of ready disinfection afterwards. It is customary to hang outside the door a sheet soaked in some disinfectant, and the practice is at all events of use as a danger-signal. It is useful to place outside the door a bath containing an active disinfectant (such as five per cent carbolic acid), so that cups, spoons, and other articles used by the patient may be placed in it before being taken downstairs to be cleaned.
The relative value of disinfectants is so largely misunderstood by the public, and a proper knowledge of them is so important in house-sanitation, that a few words on the subject should not be amiss here. A disinfectant, as its name implies, is an agent which, applied in a certain strength and for a certain time, is capable of killing the germs of infectious disease. Carbolic acid is a disinfectant when properly employed, but to sprinkle a little pink carbolic powder down a gully-hole or privy is a useless proceeding except for deodorizing purposes, and may be actually mischievous by creating a false feeling of security. The facts that require to be insisted on are as follows: - Bacteria which do not form spores are killed by five per cent carbolic acid (phenol) in five minutes, but the highly-resistant spores formed by some species of bacteria require at least twenty-four hours' exposure to this solution before they perish. It is probable that most of the germs of our ordinary fevers do not form spores, but it is not safe to assume this; indeed, in the case of small-pox, the most recent evidence points to a spore-bearing bacillus as the cause of the disease. Carbolic acid, to be an efficient disinfectant, requires to be present in the proportion of one part in twenty of the total volume of the material to be disinfected, and contact should last at least five minutes, and in the case of spore-bearing bacteria, twenty-four hours. The cheaper dark commercial brands of "carbolic acid" are mixtures of phenol, cresol, and tar oils, but cresol seems equal to phenol in disinfectant action.
The most powerful chemical disinfectant we possess is perchloride of mercury (corrosive sublimate). A solution of this salt, of the strength of 1 in 500, kills the most resistant spores in about a minute, while one of 1 in 5000 kills bacteria which form no spores, equally quickly. It is by far the surest disinfectant, but it has the disadvantage of being a very deadly poison. It has, further, for household use, the disadvantage that it must not come into contact with metals, since it damages them, and is itself, at the same time, rendered ineffective.
The majority of the so-called "disinfectants" sold under fancy names are unreliable, though many of them have a valuable deodorant or antiseptic action. Where a genuine disinfectant action is required in a short time perchloride of mercury is the safest substance to rely on; or, failing that, carbolic acid of at least 5 per cent strength.
The practice of disinfection by fumigation is much in vogue, but not much reliance should be placed on it. The old-fashioned method of burning sulphur is not thoroughly efficient, even when well carried out. Chlorine is a better aerial disinfectant, but its application is troublesome. Even in a well-sealed room it is very difficult to keep up the percentage of the gas requisite for genuine disinfection for the necessary length of time: nevertheless, such methods are better than nothing. The method, used in Paris, of spraying an infected room and its contents with a solution of perchloride of mercury of the strength of 1 in 1000 by means of a powerful force-pump termed a "pulverisateur" is a much more effective and rational procedure.
Heat is the most speedy and convenient disinfectant we possess. Only the more resistant spores of bacteria are capable of withstanding the temperature of tailing water, and this only for a short time. Moist heat is better than dry, and steam under pressure is the best of all means for disinfecting clothing and bedding on account of its rapid penetrating power. Many sanitary authorities now possess the apparatus necessary for this purpose.
The foregoing facts may now be applied to the practical disinfection of a house where infectious disease has occurred. In the case of diseases such as diphtheria or scarlet fever, where the secretions from the nose and throat are infectious, such secretions should be received on old rags and at once burnt. In typhoid fever and cholera, where the discharges from the bowel are the main infecting agents, they should be treated with a large excess of at least 5 per cent carbolic acid or of a solution of perchloride of mercury (l in 1000), and they should remain in contact with the solution for an hour or two, the solid portions being well broken up. They may then be poured down the water-closet in towns, but in the country they should preferably be deeply buried, remote from any water-supply. At the close of the illness the room and furniture should be superficially disinfected by spraying with perchloride of mercury solution (1 in 1000), or by thorough fumigation with chlorine or sulphur for twenty-four hours. If the latter has been properly done, and the room previously rendered air-tight by pasting up all cracks and crevices, the air should be nearly irrespirable when the room is opened after twenty-four hours. All bedding and hangings should then be removed and disinfected by steam under pressure. The floor, walls, bedstead, and other furniture must he well scrubbed with 5 per cent carbolic acid, or, better (except for articles made of metal), with perchloride of mercury solution (1 in 1000), the paper removed from the walls, and re-papering and whitewashing performed. During these latter processes as much fresh air and sunlight as possible should be admitted into the room, which is then ready again for habitation.