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How to choose an air purifier
Deep-clean your living space.
If there's dust lurking in your living space, it will make your need for an air purifier seem more dire than it actually is. Vacuum regularly, including furniture, and check your heating vents for lint and dust.
If you still feel like you'd breathe easier with cleaner air, then you can start doing research on an air purifier. Determine why you need an air purifier.