How to clean and naturally purify room air

This below is a $15 car air purifier, comes with a hepa filter ( for whatever gimmick it's worth, not much), in the middle of that filter is a hollow spot. Use lump charcoal, broken into smaller pieces and insert them in the hollow spot, and cover with a cutout piece of foam so charcoal dust doesn't go into the fan area.

This works marvellously to clean and freshen the air, much better than the original filter. I have a 12x12 room where the dog and I sleep in the summer as it is the only room with window ac, it used to get stuffy in the mornings regularly, no longer the case after I did this. Charcoal also removes chemical and biological poisons from the air. Even a small unit like this works wonders due to charcoal. Replace charcoal every 10 days. Use actual lump charcoal not the briquettes