i have returned to cell block c,but i cannot get any of the gas cannisters of the wall,even by useing the screwdriver.please help.

Hi bigal,

This is what Fongo stated about going back to cell block C:
Open up the location panel and go back to Block C. As before, carefully make your way up the corridor running from cell to cell - this time you want to make it all the way to the end of the hallway. Once there, press yourself right up against the wall - the robot cannot detect you here. Look up and find the gas canister hanging from the wall, and unscrew it with the screwdriver.

It might be your position to face the canister. Keep us posted if this worked.

More: I checked the Unofficial Tex site :
Work your way back down to the other end of the corridor. When it's safe, use the screwdriver on the orange canister, and Tex will take it down off the wall.

I've just done this part OK.
Is your problem :-
(a) That you can't REACH the (single I think) gas canister before being killed by the droid?
(b) That you DO reach the gas canister before being killed by the droid, but you haven't got enough time left to unscrew the canister before it kills you?
(c) It's not a matter of being killed by the droid at all, but that your screwdriver fails to unscrew the canister from the wall (no matter how much 'living' time you've got left)?

If it's (a) or (b) then it's just a matter of timing with a few hints as to how to maximise your movements & actions.
If it's (c) however, then it seems like a bug or technical problem.

Shortly after ........... Just looked at it again!!

THERE IS MORE THAN ONE GAS CANISTER !!
But only ONE that can be unscrewed!
Maybe it's neither my previous (a), (b), or (c) ... but simply that you've been trying to unscrew an "impossible" completely fixed canister ???

thanks,

i think i am trying to screw the wrong canisters,there are about four or five,i think i need to be at the other end of the block.
i will try this.
thanks.

The one you want is at the far end of the long row of cells in Block C. This means you have to dodge the robots again. It should be above your head in the centre of the short wall at the end of the cell row. I don't remember if there are multiple cannisters located there, but try the one in the middle of the wall.

Fongo is absolutely right.
If you are still stuck .............

You FOLLOW the droid (not TOO close to it ... I think it's got eyes also at the back of its head! ) down the fairly long double row of cells in block C.
It's impossible to reach the end (short wall) in one go without being killed. There is an open (safe) cell about 1/2 way down and another about 2/3rds way down ... both on the LEFT.
If you can make it to the further one in one go ... FINE. If not, it is easily done in 2 steps.
Once you are in this safe cell (the furthest you can go safely) watch the droid carefully. Soon (BUT NOT IMMEDIATELY) after he has passed from left to right, dash out to the left and unscrew the canister on the short wall immediately in front of you (you have to look up a bit for this!)

There ARE several (maybe 4 or 5) to the LEFT of this (vital) canister ... ignore them; they can't be unscrewed (welded to the wall or something).