Humidifying air purifiers

Most air purifiers sold in Japan come with a humidifier built in. The ones you see most on Amazon are Daikin's MCK series, Sharp's KI series and Panasonic. Their ion technologies are called Streamer (ストリーマ), Plasmacluster (プラズマクラスター) and nanoe (ナノイー) respectively, and in everyday use you can't really tell which is better.

When reading the specs, note that the room size is given in jō (畳), and that the humidifying area is a notch smaller than the purifying area and comes as two figures: one for a wooden Japanese-style room (木造和室) and one for a prefab Western-style room (プレハブ洋室). If you live in a wooden house, go by the wooden figure, and picking one size up from your room is the safe bet.

Dust filters these days are mostly rated to go about ten years without replacement, so the routine upkeep is mainly the humidifier part. Top up the tank every day, and every so often soak the humidifier filter and tray in citric acid to remove scale; leave them too long and they start to smell. In summer you don't need humidifying, so just switch it off and run the purifier only.

These brands put out new models pretty much every year, and last year's models get marked down to clear stock. The features barely differ, so if you want to save money, go for an older model. Amazon's Prime Big Deal Days (プライム感謝祭) and Black Friday often have deals too.