“Stay inside” is no longer a safe way to escape from unhealthful air. Recent studies have shown that indoor air pollution is almost always two to five times worse than outside pollution. Buildings create their own pollution, and the air inside many homes, office buildings, and schools is full of pollutants including chemicals, bacteria, and smoke. These pollutants are causing a group of unpleasant and dangerous symptoms such as eye or throat discomfort, headache, dizziness, and tiredness, which experts call “sick building syndrome.”

     There is a possible solution to the problem of “sick” buildings. A scientist at NASA was trying to find ways to clean the air in space stations. He discovered that houseplants actually remove pollutants from the air. But we don’t know enough yet. There are many questions. For instance, which pollutants can plants remove? Which can’t they remove? How many plants are necessary to clean the air in the room? When we are able to answer these questions, we might find that plants offer an important pollution-control system for the 21ˢᵗ century.