The LM carried enough oxygen, but that still left the problem of removing carbon dioxide, which was absorbed by canisters of lithium hydroxide pellets. The LM's stock of canisters, meant to accommodate two astronauts for 45 hours on the Moon, was not enough to support three astronauts for the return journey to Earth. The CM had enough canisters, but they were of a different shape and size to the LM's, hence unable to be used in the LM's equipment. Engineers on the ground devised a way to bridge the gap, using plastic covers ripped from procedure manuals, duct tape, and other items available on the spacecraft. NASA engineers referred to the improvised device as "the mailbox". The procedure for building the device was read to the crew by CAPCOM Joseph Kerwin over the course of an hour, and was built by Swigert and Haise; carbon dioxide levels began dropping immediately. Lovell later described this improvisation as "a fine example of cooperation between ground and space".
The LM carried enough oxygen, but that still left the problem of removing carbon dioxide which was absorbed by canisters of lithium hydroxide pellets. The LM's stock of canisters, meant to accommodate two astronauts for 45 hours on the Moon, was not enough to support three astronauts for the return journey to Earth. The CM had enough can,isters, but they were of a different shape and size to the LM's, hence unable to be used in the LM's equipment. Engineers on the ground devised a way to bridge the gap, using plastic covers ripped from procedure manuals, duct tape, and other items available on the spacecraft. NASA engineers referred to the improvised device as "the mailbox". The procedure for building the device was read to the crew by CAPCOM Joseph Kerwin over the course of an hour, and was built by Swigert and Haise; carbon dioxide levels began dropping immediately. Lovell later described this improvisation as "a fine example of cooperation between ground and space".