What happens is when your ac is on, it is generally a closed room and the level of oxygen reduces gradually, the curtains, bed sheets etc attracts lots of dust duing time when room is open to atmosphere, but when ac is on and we feel the low temprature and body feels good but on the contrary we inhale lot of dust, becteria, ., carbondioxide etc which is very harmful for all especially children, to come up with this problem one MUST buy a Ac which has a air purifier now a days for metro town it is mandatory to have such a