Santa Farts to get around?

I left some cookies and milk out fo Santa last night and lo and behold when he came he ate the cookies and drank the milk. I found out why one is supposed to leave cookies and milk for him. The milk gives him gas so he can fart and propel back up the chimney. Its really true because I witnessed it last night and I still have all the windows open to air the house out 12 hours later. Why does Santa's farts smell so bad?