The air we breathe

My family has tried a couple of air purifier machines at home. In Manila one would think this would work, but I am not sure if it really does. In Sydney, when I moved here, the family I lived with used air purifiers as well. One of the kids had asthma and the parents thought that by turning the machine on at night this would have the child avoid an asthma attack. The question are air cleaners safe really? It really depends on how one is convinced to use them at home, or whether the machines are used properly the way they are meant to be. For me, I think I don’t really mind not having it. I suppose it is all just about preference.