smoke
煙 centers on visible airborne particles from burning: smoke. The concept extends naturally to anything smoky or hazy.
煙 combines 火 (fire) with 垔, which likely contributes the sound and the idea of something rising or filling the air, together suggesting smoke from fire.
Fire 火 on the left and a shape 垔 that looks like a heavy lid trapping rising fumes: together they make smoke.
For エン, picture smoke rising from an engine: engine -> エン, and the fire 火 produces thick smoke.
tobacco; cigarette; cigar
smoking (tobacco)
smoke; fumes
abstaining from smoking; quitting smoking
chimney; smokestack; funnel (of a ship); stovepipe
steam
emitting smoke; fuming
smokescreen
separation of smoking and non-smoking areas
beacon; skyrocket; signal fire; smoke signals
(tobacco) pipe with metal tipped stem; kiseru
(eruption of) smoke
kiseru; Japanese smoking pipe
dislike of smoking
gunpowder smoke
to smoke (e.g. fire); to billow smoke; to smoulder; to smolder
mist over a body of water; spray
smoke and fumes (e.g. from cooking)
smoky
cloud of dust