This could be difficult to apply for such an extended period of time, but I generally have good results by just breathing exclusively through my mouth. Pretend you’re underwater and breathing through a snorkel.
This technique has gotten me through many a fart and temporary sewage/fertilizer exposure.
Easy, just send him back in time.
https://store.steampowered.com/app/1349230/5D_Chess_With_Multiverse_Time_Travel/