Actually, one of the best ways to go is whole-house HEPA filtration. For roughly $800 installed, you can filter a 3000 sq foot home. These units are certified to remove particles down to .3 microns (this includes viruses). Look at Fantech.net under HEPA filtration. The Sharper Image unit received bad marks from Consumer Reports and it sued CR, lost and was ordered to pay 400K back to CR for filing a "meritless suit" Ozone is also not recommended for asthma sufferers and has actually been reported to cause asthma. This info is all available with a Google search.
Disclaimer - I do have a connection to the ventilation market through the electrical industry.
Disclaimer - I do have a connection to the ventilation market through the electrical industry.