Iskar gas, wani muhimmin "man fetur na gadoji," galibi yana ɗauke da hydrogen sulfide (H₂S) da mahaɗan sulfur na halitta (mercaptans, COS), waɗanda suke da guba, suna lalata, kuma suna haifar da SOx mai cutarwa idan an ƙone su. Don haka, rage sulfur (zaƙi) yana da mahimmanci.