Start in upper tunnels. You will want to stand in this corner (right up against the corner on the left side):
This corner.
Your aim needs to be pixel-perfect. Aim on the dark bottom edge of the door trim, in between the middle blotch and the smaller blotch immediately to its left. You need to CROUCH and then JUMP THROW.
This is probably the hardest smoke on the website, so here's even finer detail:
In even finer detail:
Here's where your smoke should land, ideally:
