It's not supposed to, but the pressure grid is 4x4, and this DOES happen, unfortunatly. You have to make a 4 thick wall. And yes, some powder may fall through without air, falling powder dislocates some air and creates pressure.
@Wazabi-Bros(View Post) Hmm? Let me look into this better... Hmm, you're right. All I know is that it's not intended, it's hard to if not impossible to fix, and it has been here since as long as I can recall.
the problem is the way tpts movement code works, if the weight of an object is over 50 then it will go through and solid that is 1 pixel thick, it is known bug and it get fixed with savask fixing the movement code in realistic mode/if simon changes it in tptpp.