Have experienced this while seated in window seat also on some LOT Embraers, AA Embraer 145, LH 747-400, LH A380, LH A320, AC B777. So this is nothing new.

Most worrying what I have seen has been on United A320 when during taxi and takeoff from AC vents started coming something like smoke/fog (especially during takeoff when engines were running at max power) that subsided shortly after takeoff... It was not pleasant flight...