Closed living environments with poor circulation of air are methodical killers. Carpets, wallpaper, and couches are ideal repositories for household dust. Even pressure can bring on symptoms--students at "star schools" for brighter students have a higher rate of asthma, and some find it difficult to breath whenever a test approaches.
例如：日常用品嗆鼻的漂白水、殺蟲劑；封閉、空氣流通不佳的居室空間；地毯、壁紙、沙發是室內灰塵最好的儲存所；壓力也會致病，明星學校學生罹患氣喘的比例偏高，有些學生甚至每到考前，一緊張就氣喘不止。