The fire on the west side of the earth made the air too smoky to ENJOY.
禁 (prohibition) + 煙 (smoky)
= 禁煙 (no smoking)
喫 (enjoy a drink and a smoke) + 煙 (smoky)
= 喫煙 (smoking)
the act of smoking. You'll see this on signs a lot, meaning 'this is the smoking section.'