CHAPTER XIII
DISINFECTION AND FUMIGATION
DEFINITIONS
Disinfection
When an object is contaminated with so-called pathogenic germs it is said to be infected. To disinfect an object it is necessary to destroy the microörganisms. The destruction of all so-called pathogenic germs, whether in the substance of the object or on its surface, is called disinfection. All lower forms of animal and vegetable life are destroyed in sterilization, while in disinfection only the germs which, from the medical standpoint, are the cause of dis-ease, are destroyed. The agent used in disinfection is known as a disinfectant or germicide.
Sterilization
The destruction of all germ life in or on an object is known as sterilization. From the standpoint of hygiene sterilization is unnecessary except in dis-eases such as anthrax, tetanus, and other spore-bearing dis-eases, the spore being highly resistive and not so easily destroyed as the vegetative cells. Sterilization will disinfect but disinfection will not necessarily sterilize. Disinfection is thoroughly efficient in almost all cases. Sterilization destroys all life.
Antiseptic (Anti, against, and septos, putrid)
An antiseptic prevents putrefaction but does not necessarily destroy the microörganisms. A substance may act as an antiseptic by delaying or preventing the processes of decay and decomposition, but still not be a germicide. In other words, anything that will hinder the development of germ life acts as an antiseptic. Thus cold has a preservative action, although it will not destroy the microörganisms. A disinfectant may be diluted and used as an antiseptic. A 10% solution of formalin is a good disinfectant and will kill bacteria in a relatively short space of time, but formalin in a solution of one to fifty thousand will be a very good antiseptic. The germination of anthrax spores may be prevented by the use of bichloride of mercury in as weak a solution as one to three hundred thousand, but it will require a solution of one to one thousand to destroy the spores. A disinfectant is also an antiseptic but an antiseptic is not a disinfectant.
Asepsis
Asepsis is an absence of putrefactive bacteria. This may be accomplished without the use of germicidal agents by cleanliness which excludes all so-called pathogenic germs.
Insecticide
An insecticide is an agent capable of destroying insect life. Many of the germicidal agents are also insecticides. There is a great difference in the resistance of different insects. Formaldehyde is a good germicide but is not an insecticide. There are four ways of using insecticides. In liquid form, powder, vapor form and those placed in food to be eaten by the insects.
Germicide
A germicide and a disinfectant are the same for they both destroy germ life. Many germicides are so powerful that they completely sterilize or destroy all life.
Deodorant
A deodorant is not in any sense a disinfectant and has no power to destroy germ life. It is an agent which neutralizes unpleasant odors. A disinfectant destroys germs but does not necessarily destroy odors. A deodorant must not be confused with a substance having pungent odor which merely substitutes one odor for another. A deodorant destroys the unpleasant odor.
Fumigation
Fumigation is a means of disinfection by use of fumes or gases, and is used generally for the purpose of destroying germ life only on the surface of objects. For this reason fumigation should not be used as a substitute for disinfection. Formaldehyde and sulphur dioxide are used largely for fumigating purposes.
Of these two gases formaldehyde is the better since it is not poisonous, does not injure the surface of objects and will not damage the most delicate fabrics nor destroy colors. Sulphur dioxide is very destructive and therefore less desirable. However, all the gaseous agents lack sufficient penetrative power to accomplish more than a surface disinfection. Formaldehyde is a good germicide and this adds to its efficiency.
To obtain the desired results in fumigating there must be special attention given the preparation of the rooms or spaces to be fumigated. All objects in the room should be so exposed that the gas may readily get to all surfaces. All furniture and other objects should be moved into the room away from the walls and all doors and drawers of bureaus and boxes should be opened so the gas may find free access to every nook and corner. Much of the gas may escape through cracks and crevices, therefore special care must be exercised that these openings are all properly closed before the fumigation is started. In view of the fact that the gas is non-destructive there is no harm done even to the most delicate materials.
The best results are obtained from the formaldehyde when the temperature of the room is 65° F. or over, with a relative humidity of at least 60%. While formaldehyde has the power to kill spores it is not considered sufficient to disinfect in such dis-eases as anthrax and tetanus.
Formaldehyde gas kills all forms of microörganisms almost instantly but is not particularly destructive to higher form of life. It produces a marked irritation in the mucous membrane of the respiratory tract which may result in death to animals exposed to the gas for any length of time. It is not considered an insecticide.
In fumigating a room with formaldehyde great care must be exercised that the individual does not remain in the room after the gas begins to be liberated. After the process of fumigation has been completed the windows and doors should all be opened that the gas may escape. It is always best to have the doors and windows open from the outside so that it will not be necessary for any one to go into the room until the gas has blown out.
AGENTS OF DISINFECTION
Physical Agents
The physical agents of disinfection are sunlight, electricity, pressure, dry heat, burning, boiling, and steam.
Chemical Agents
Chemical agents of disinfection are divided into two divisions—gaseous and liquid disinfectants. The gaseous disinfectants are: formaldehyde gas, sulphur dioxide gas, hydrocyanic acid gas, chlorin, oxygen, and oxone.
Some of the most important liquid disinfectants are metallic salts, bichloride of mercury, silver and zinc salts, coal-tar creosote, carbolic acid, phenol, lysol, creolin and formalin.
MEANS OF DISINFECTION
Natural Means
Nature’s means of disinfecting are by dilution, sunlight, desiccation, time and antibiosis. The direct rays of the sun are Nature’s greatest germicide. Few of the microörganisms will live in the direct rays, but there are none that will withstand them for more than a few hours. Germs can not withstand the effect of dryness. Thus we see there is in Nature that which works as a most efficient germicide. The combination of sunlight and dryness forms a most desirable means of disinfection. When germs become attenuated through the effects of these natural processes they do little harm when introduced into the body.
One of the most important adjuncts to the work of disinfection is personal cleanliness and sanitation of the environment.
Other Agents
Fire is not a practical disinfectant. It can be used only with those articles that are of little or no value since the article that is being disinfected is destroyed. The burning of all refuse and garbage is by all means the best method. Burning is the most satisfactory and cheapest method in disinfecting sputum and other excreta from the body, and in disposing of articles of little value saturated or contaminated with such.
The dry heat method of disinfecting requires specially built apparatus such as dry air sterilizers. This form is not practicable for use in disinfecting fabrics and other materials that are destroyed or injured by extremely high temperature required to destroy the germ life. Metals are easily injured by this method as they are likely to be scorched. All forms of life are destroyed in an hour’s time when exposed to a temperature of 150° C. Such articles as glassware will withstand this heat or even higher and may be thoroughly sterilized in from one to two hours. This insures proper penetration and sufficient heat to completely destroy all life.
Boiling is one of the most satisfactory and easiest methods of disinfecting. Continuous boiling for an hour in water at 100° C. will result in the destruction of most germs of the so-called infectious dis-eases. There are some of the spores, such as those of anthrax and tetanus, that will survive the most strenuous processes of boiling. However, most of the germs will be destroyed before the boiling point is reached.
Boiling is the best method to be used in disinfecting bedding, body linen, towels and other fabrics which will not be harmed by this process. There is a great variety of articles that may be disinfected in this way, such as utensils and bed pans. The surfaces of the floors, walls, beds, and other objects may be cleansed with boiling water. In this use it is advisable to add some disinfectant to the water.
Steam is not only a disinfectant but it is also a sterilizing agent. All forms of germ life, including spores, are completely destroyed. It is therefore our best known disinfectant. There are many objects that are injured and some ruined by steam, such as silk, wool, furs, oilcloth and rubber goods, and articles containing varnish or glue. There is danger from staining and running of colors. Disinfection may be either with streaming steam or with steam under pressure. For the use of streaming steam no particular device is necessary. Some means of providing the steam and some place to hang or place the objects and articles to be disinfected are the two essentials for this method. It is not necessary to have an air-tight place. To use steam under pressure there must be a specially constructed apparatus. There are many such devices on the market and they are used in institutions where it is found necessary to disinfect with steam.
Sterilization may be accomplished in twenty minutes with steam at about one atmosphere of pressure which will give a temperature of about 120° C. A temperature of about 125° C. is obtained with the pressure at about twenty pounds to the square inch. This reduces the time for sterilization to about fifteen minutes.
Other Disinfectants
Carbolic acid which is a good antiseptic but a comparatively mild germicide is another disinfectant. It has very little penetrating power and is of most value in a 3% to 5% solution for washing floors, walls and woodwork. The cresoles are more powerful and effective disinfectant than carbolic acid. The most common of this group are: creoline, lysol, and saprol. Their use is about the same as that of carbolic acid. Bichloride of mercury may be used in a solution of from one to two thousand, to one to five hundred and forms a very good disinfectant. It kills germs but corrosive sublimate will kill spore-bearing bacteria only in a solution of one to five hundred. In weaker solutions it forms a very good antiseptic. Lime forms a very good disinfectant, especially for excreta, cesspools and cellars.