When summer comes, the air is stuffy and the temperature is so high. Thanks to the invention of air-condition, people are no longer suffer to the hot weather, they can stay at the indoors and enjoy the coolness that air-condition brings. But the problem comes, when people count on air-condition for a long time, their bodies will be weaker. Some people feel dizzy and have no strength to do their work, some people are easy to catch the cold. All of these symptoms are typical illness which is from air condition. Though air-condition brings us comfort, we will get sick if we use it all the time. We need to go outside often, even is hot, what’s more, taking exercise is needed. The natural environment is suitable for us to live in, we can’t count on air-condition for a long time.