It can also be used to purify hydrogen in flame ionization detectors. Maximum pressure is 100 psig. The Big Trap has a 400 cc total volume of cobalt-free CoFree™ indicator and molecular sieve 5A in a clear acrylic tube. The CoFree changes from greenish-yellow to blue at low relative humidity to warn of leaks in the gas stream. Our unique O-ring design allows hand-removal of the cartridge without disconnecting the fittings from the line, while a plastic insert at each end keeps the packing from spilling. 1/8" fittings. Dimensions 2-1/4" x 17" including fittings.