After the problem realized when trying to put up three astronauts for an extended stay in the Apollo 13 LEM, namely that the square CM CO₂ scrubbers didn't fit in the LEM's slots, were they redesigned?

Apollo 13 "Mailbox" CO₂ scrubber adapter rig

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    $\begingroup$ A "simple" change in shape can have multiple knock-on effects (volume, flow rate, etc.), all of which would have had to be reviewed and approved by the configuration management board, which wasn't a fast process. Meanwhile, no work could be done on the spacecraft until the change was approved. The better option was to ensure that such an incident wouldn't reoccur. $\endgroup$
    – John Bode
    Commented Dec 16, 2016 at 22:32

1 Answer 1


No, the scrubber design was not modified.

The Apollo 14 press kit has a list of the changes made after Apollo 13:

The major changes to the command/service modules include adding a third cryogenic oxygen tank installed in a heretofore empty bay of the service module, addition of an auxilliary [sic] battery in the service module as a backup in case of fuel cell failure, removal of destratification fans in the cryogenic oxygen tanks and removal of thermostat switches from the oxygen tank heater circuits. Provision for stowage of an emergency five-gallon supply of drinking water has been added to the command module.

(and several more paragraphs)

The file doesn't mention any changes to the CO₂ scrubbers.

A thread on Yahoo claims no changes were made, but offers no references. One of the posters there does say he has an Apollo 16 LM CO₂ canister, and it looks identical to the Apollo 13 items.

The Lunar Module, LM 10 Through LM 14, Vehicle Familiarization Manual (large PDF) shows a drawing of the Environmental Control System (page 3-55/page 89 of the PDF). LM 10 flew with Apollo 15. The drawing still has round covers for the scrubber canisters, like the photo below. LM ECS with captions

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    $\begingroup$ There was no real need to unify the designs, given that after Apollo 13, a proven procedure to build an adapter was available. $\endgroup$ Commented Jun 16, 2016 at 3:59
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    $\begingroup$ In addition to @RussellBorogove I think it was also simpler to manufacture a properly built, ready to use adapter rig and stow it away. Also don't forget that during a mission going to plan the LEM was jettisoned before leaving lunar orbit. So on the journey home the LEM was not available as a life raft. So provisioning for keeping the CM functional in case of a SM failure was priority, since there'd not always be a LEM around to retreat to. $\endgroup$
    – datenwolf
    Commented Jun 17, 2016 at 19:20
  • $\begingroup$ According to the Apollo Flight Journal: "New procedures were planned and included in the checklist procedures carried for the missions [...] This included a diagram showing the arrangement of the tape and plastic bag adapter for using the Command Module lithium hydroxide canisters in the Lunar Module's Environmental Control System. Despite the long-standing rumors to the contrary, there was no effort to standardize the canisters between the two spacecraft." Unfortunately the AFJ doesn't show said diagram. $\endgroup$ Commented Nov 23, 2023 at 12:02

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