I use dehumidifier when its rainy season like now. Sometimes kasi yung carpet basa because of my shoes. At bumabaho yung carpet. True the air-con is also a dehumidifier but you can't just let the air-con on always.
Sa Japan Home mura lang dehumidifiers. 4 pcs. 88 pesos lang.
Ionizer hindi pako nakagamit.
useful links.
http://en.wikipedia.org/wiki/Dehumidifier
http://en.wikipedia.org/wiki/Ionizer