Smoking in the terminals is prohibited by Hong Kong law, except in the designated smoking lounges.
There are 2 smoking areas located between gates 210 and 212 near the escalator on both arrivals and departure levels.
Arrivals: Smoking areas are located near gates 60, 20, 21.
Departures: Smoking areas are located near gates 60, 64, 43, 29, 25
Many reports of these areas being “toxic” unventilated and uncomfortable. Seems you’ll be in for a quick fix then back to fresher air inside the terminal.