YOU SAID:
Fumes and gases can be dangerous
INTO JAPANESE
煙やガスは危険である可能性がある
BACK INTO ENGLISH
Smoke and fumes can be dangerous
INTO JAPANESE
煙やガスは危険です
BACK INTO ENGLISH
Smoke and gas are dangerous
INTO JAPANESE
煙とガスは危険です
BACK INTO ENGLISH
Smoke and gas are dangerous
That didn't even make that much sense in English.