Cleaner Air

I often wonder if I could create an completely clean air in my home if it could help my sons asthma. He has been have a difficult time with his asthma lately. I know there are some things I can do to improve the air quality in my home. Air purifiers, quality vacuum cleaners and humidifiers are ways I know can help.
I have heard the Dyson vacuum cleaners are good. They claim that most other vacuums expel the dirty air that is sucked up then blown back into the air. This is what was happening to my vacuum. Not only was it expelling bad air it wasn't even holding the dirt in. The Dyson web site where I got this information also has a visual of how this happens. I found it interesting.
This site also has information on the Dyson Airblade hand drier. According to this site most public hand driers suck the dirty bathroom in, heat it up, and then blow it back on to your hands. Yuck! I never realized that is what was happening. They also have given a visual for this.
So, I am seriously considering buying a Dyson vacuum cleaner and I may decided to pass on using the public bathroom hand driers unless I see the words Dyson on it.