Prototype of the "mail box" constructed at the Manned Spacecraft Center to remove carbon dioxide from the Apollo 13 Command Module is displayed in the Mission Control Center. The 'mail box' was constructed when it became apparent that carbon dioxide was prevalent in the Command Module and the spacecraft's lithium hydroxide system was not removing it sufficiently. Looking at the "mail box" are, from left: Milton Windler, shift 1 flight director; Dr. Donald (Deke) Slayton, director of flight crew operations, MSC; Howard Tindall, deputy director, flight operations, MSC; Sigurd Sjoberg, director, flight operations, MSC; Dr. Christopher Kraft, deputy director, MSC; and Dr. Robert Gilruth, director, MSC. Source: NASA.