Typically, air purifiers and related items such as humidifiers and electric air cleaners are not covered by Medicare. However, Medicare may be able to cover a humidifier, when medically necessary, if used with some forms of durable medical equipment (DME). Under that scenario, I would suggest confirming with Medicare directly to see what would be necessary to meet those requirements.
I don’t know how much they cost brand new, but if expense tolerance is a large concern and one is desired, there may be discount ones or pre-owned ones that may be available for a low price that is tolerable on websites such as amazon, ebay, etc. I would suggest taking a look in those areas for an alternative way to save money on the purchase of an air purifier.
I hope the information is helpful – please feel free to contact me with any other questions. Thanks very much.