The humble window screen is not usually thought of as a health measure. However, screens for windows and doors are still among the basic tools used to protect against germs and infection. The early domestic sanitation tools first promoted 100 years ago—refrigeration for food, the porcelain toilet, and screens for windows and doors—are taken for granted now.
Using glass in windows was a fine solution to a problem that had plagued people for centuries. The windows needed to let in light but keep out air (when it was cold) or let it circulate (in hot weather). Before germ theory was accepted as explaining the causes of many diseases, it was believed that much disease was the result of miasmas, bad airs that rose from the ground at night and spread out over the land. Because miasmas could enter houses and make people ill, it was safest not to breathe night air but rather to stay behind shut windows and doors regardless of the weather. By the end of the 1800s, when germ theory was accepted as the explanation for many diseases, the attitudes of physicians, the public health community, and the public toward air in their houses changed.
This change in attitude led to the mistaken notion among the lay public that breathing fresh air was especially healthful and therefore houses should be well ventilated. People soon faced a conflict between the desire for fresh air and the new teaching of the dangers of the bites of mosquitoes and of contamination by flies on food. The solution was ready to hand—wire cloth set into frames to be put onto windows and doors, creating the window screens and screened doors we are still familiar with. The metal mesh allows excellent circulation while keeping out insects.
Screens were also used on porches. Although in the early years architects and designers often decried the look of screened-in large verandas and sleeping porches, the owners recognized the benefits, and it was the rare porch in insect-infested places that was not at least partially screened. These porches are everywhere today, although we now think of them not as havens from disease but as places to relax, visit with friends, or read.