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is a Hepa Fliter Air Purifier or Ionizer be use low astma people?
You do not want an ionizer or anything which generates ozone. Ozone is a well known irritant and is especially bad for asthmatics. A good HEPA-standard air purifier will serve you well.
Ionizers have horrid reviews so far as actually removing particulate matter from the air.
Here’s an EPA article, but you can also look up the Consumer Reports review at your local library.