[6] When Oakland High School in California moved into a new building, the students and teachers noticed a strong smell. Then almost half of the students began to have headaches and sore throats and very tired. This three symptoms disappeared on weekends. The cause was mystery. Experts came to investigate and find the cause of the sickness. Finally, they discovered that the air in the building was not safe to breath. They were surprised to find that the cause were the shelves in the school library! These shelves were made of particleboard. That is, an inexpensive kind of board that is made of very small pieces of wood held together with a chemical. This is just one example of a modern problem that is most common in cities- indoor air pollution.

[4] People have worried about smog for many years, and the government has spent billions of dollars to try to clean up the air of big cities. In addition, now we find that there is no escape from unhealthful air. Recent studies have shown that air inside many homes, office buildings, and schools are full of pollutants: chemicals, bacteria, smoke, and gases. These pollutants are causing a group of unpleasant and dangerous symptom that experts call "sick building syndrome". A "sick building" must be a small house in a rural area or an enormous office building in an urban center.

[2] A recent study reached a surprisingly conclusion: indoor air pollution is almost always two to five times worser than outside pollution! This is true even in buildings that are close to factories that produce chemicals. The solution to this problem would seem very clear: Open your windows and stay out of modern office buildings with windows that don't open.

[8] Unfortunately, the solution might not be so simple. Better ventilation- a system for moving fresh air- can cut indoor air pollution to safe level, but lack of ventilation is seldom the main cause of the problem. Experts have found that buildings create its own pollution. Imagined a typical home. The people who live there burn oil, wood, or gas for cooking and heating. Cigarettes, pipes, or cigars might be smoked. They use chemicals for cleaning. They use hundreds of products make of plastic or particleboard, these products- such as shelves in Oakland High School give off chemicals that we can't see but that we do breathe in. And in many areas, the ground under the building might send a dangerous gas called radon up the home. The people in the house are breathing in a "chemical soup" and medical experts didn't yet know how dangerous this is for the human body.