Any mask with activated carbon[1] can filter basic odors. For more gases, get a chemical cartridge[2].

[1] https://www.homedepot.com/p/HDX-N95-Disposable-Respirator-3-... [2] https://www.homedepot.com/p/3M-OV-AG-P100-Professional-Multi...

It seems to greatly reduce odors for me? Maybe placebo effect but it does seem to help a lot.

Also when someone farts it’s the particles that smell bad, not the air itself