Do You Need Air-Conditioning?
IT IS a hot, sultry day. The sun beats mercilessly down on you as you drag yourself home from work. But when you open the front door to your house, a wave of cool, refreshing air welcomes you. Ah-h-h-h, air-conditioning! What a relief it can be!
But say it is a cold, wintry day, and when you open the door of your house, a wave of warm, soothing air welcomes you. Do you thankfully say to yourself: ‘Ah-h-h-h, air-conditioning’?
Perhaps not. Nevertheless, it would be an appropriate response. “Air conditioning,” explains World Book Encyclopedia, “cools the air when the weather is hot. It warms the air when the weather is cold.”
However, the term “air-conditioning” is generally applied to the cooling of the air in an enclosed environment, whether that be a house, an office building, an auditorium, a movie theater, an automobile, a bus, a train, or some other enclosed space. Yet, air-conditioning does more than change the air’s temperature; it also controls the air’s movement, cleanness, and humidity, or moisture content.
But what produces the excess heat and humidity in an enclosed environment? Of course, the main source of the heat is often the sun. Yet, you or other persons with you in the home, office, automobile, or other enclosed area are also responsible. This is because we humans are heat- and humidity-producing machines. The more we exert ourselves, the more heat and humidity we create. Even when we sit quietly, our bodies produce some degree of heat and humidity.
So for us to be comfortable, the heat and humidity we give off has to be removed at the same rate that it is emitted. If it is removed too fast, we will be too cold. If it is taken away too slowly, we will be too hot. Just to remove the heat and humidity produced by a hundred people sitting quietly in a large room takes, in technical terms, about three tons of cooling, or 36,000 Btu’s (British thermal units) per hour.
One Btu is roughly equivalent to the heat emitted by a burning match. (As a comparison, 252 calories represent the same amount of heat as one Btu.) Thus, the heat that a sedentary person gives off is about equivalent to that of 360 burning matches! But adding to the significant heat that a group of people creates in an enclosed area is the heat created by the lights and other electrical appliances that may be operating. So the advantage of air-conditioning can easily be seen.
Pros and Cons
Besides creating a more pleasant inside environment, air-conditioning may be beneficial to your health, especially if the equipment is properly used and maintained. It may eliminate heat rash, and since it often filters out pollen, it may provide relief for hay-fever sufferers. Especially for older ones, moderating the extremes of temperature can be a health benefit, and so is the replacing of stale air with fresh and the removal of dirt and dust, which air-conditioning accomplishes.
However, at the same time, modern air-conditioning, using refrigeration, can cause health problems. Many have been made sick by extreme variations between outside temperatures of over a hundred degrees Fahrenheit [40° C.] and inside temperatures of below 78 degrees Fahrenheit [26° C.] created by air-conditioning. In fact, for this reason some have declined to use modern air conditioners in favor of ceiling fans and have apparently benefited as a result.
On the other hand, air-conditioning is said to contribute to greater productivity of office workers. It also helps delegates attending conventions in an indoor arena or auditorium to be more attentive. No doubt you will agree that it is a struggle to keep alert when such facilities are hot and stuffy.
Air-conditioning is also vital to the successful operation of many industries. In the food industry, air-conditioning has especially been an asset. It makes possible the storage of foods throughout the year by preventing the growth of bacteria that cause spoilage. It keeps flour from molding in bakeries. And it is utilized to make cheeses. At one time Roquefort cheese could be made only in certain caves in France that had cool, moist air. But with air-conditioning, which duplicates the environment in the caves, similar cheeses can be produced elsewhere.
However, modern air-conditioning has also been implicated in the death and sickness of many. For example, in 1976, during a convention of the American Legion, 182 Legionnaires contracted what was later identified as Legionnaires’ disease, and 29 died. Regarding the spread of this disease, The New Encyclopædia Britannica noted: “It is suspected that contaminated water in central air-conditioning units can serve to disseminate Legionella pneumophilia in droplets into the surrounding atmosphere.” Inadequately maintained central air-conditioning systems have contributed to contaminated air that has also caused other sicknesses.
Filling a Need
Many people feel a real need for air-conditioning. In the past, wet grass mats were hung over windows or doors in the summer, and the incoming air was cooled as it evaporated the moisture. About 500 years ago, the first mechanical fan was built. It provided relief from the heat by circulating the air. Even today many people find that all they need to keep cool in the summer is the ventilation that a good fan provides.
In desertlike areas where the humidity is low, many enjoy an inexpensive method of cooling. In such a system, the outdoor air is sucked through a wet fiber mat, and the air is thereby cooled before it enters the building. With this type of cooling, though, the indoor air has to be allowed to escape at the same rate that cooled air is brought in. Usually several windows left slightly open will suffice. However, this form of air-conditioning has often proved unsatisfactory because the moisture content of the air is raised to uncomfortable levels.
A need, therefore, was filled when a means was developed in recent times to refrigerate air. Actually, the operating principle of a modern air conditioner is similar to that of the household refrigerator that is used to keep food cold. Thus, the air-conditioned building—perhaps your home or office—becomes, in effect, one large refrigerator.
To lower the temperature of the inside air, warm air is cooled as it is circulated. To accomplish this, a liquid but volatile refrigerant is circulated through a set of evaporator coils. As a blower passes the warm air over these coils, the refrigerant evaporates and absorbs the heat, thereby cooling the air. This conditioned air is then returned to the area that is being cooled. Some of the moisture is also removed when the air is cooled; it condenses on the cold evaporator coils and drains off.
In the meantime, the refrigerant, which vaporized because of its absorption of heat, passes into a compressor. There it is pressurized. It is then forced through condenser coils, where it gives up its heat and returns to a liquid state. The heat is expelled from the building, and the refrigerant circulates again through the evaporator coils to continue the cooling process.
The process of conditioning air by means of refrigeration is of relatively recent origin. An air-conditioning unit expressly for human comfort was first used in a motion-picture theater in 1922. The first air-conditioning system for trains was installed in 1931, and in 1939 units were first put in automobiles. The following year, units were introduced in buses. Homes and apartments began to use air-conditioning during the 1930’s.
The need people feel for air-conditioning obviously differs. However, there is a range of temperature that most people find comfortable. From 72 degrees Fahrenheit [22° C.] to 78 degrees Fahrenheit [26° C.] is a typical comfort zone, with relative humidity from 40 percent to 60 percent. When the weather is cold enough to require heating, most people will be comfortable when the temperature is from 72 degrees Fahrenheit [22° C.] to 76 degrees Fahrenheit [24° C.].
On the other hand, when it is hot outside, most will be comfortable when air-conditioning keeps the inside temperature from 76 degrees Fahrenheit [24° C.] to 80 degrees Fahrenheit [27° C.]. But if the outside temperature is extremely high and one is frequently going in and out, it might be wise for the sake of one’s health to keep the inside temperature somewhat higher than usual.
Do You Need It?
So, depending on your circumstances, air-conditioning may provide you with more comfortable surroundings. True, there are some areas in the world where it is not needed or even desired. Or purchasing an air conditioner may not be economically feasible for you.
However, you may decide that the benefits you could derive from air-conditioning are worth the expenditures required to have it. If the unit is properly selected, sized, installed, operated, and maintained, it can serve you well for a long time with minimal cost and, indeed, increase your comfort.