Galacticraft Oxygen Sealer problem in Attack of the B-Team Posted February 24, 2014 · Edited February 24, 2014 by arriej your windows are from the default mc glass? And everything above the blue lamps is blocked off? try placing more then one. Because one sealer only covers around 1200 blocks. (i had to put more in one room first and after then it worked with only 3 sealers.) Some shapes are harder to seal then normal squares.