Swigert counted down five, four, three, two, one.” Lovell pressed the big red engine button set in the bulkhead and once again felt the vibration below his feet. “Ignition,” Lovell said to his crew-mates.
There was now cause for optimism in Mission Control. At the TELMU station, where the Lunar Module’s environmental signs were being continually monitored, the readings of the carbon dioxide concentrations aboard Aquarius were steadily dropping all day long.
Jack Lousma – One of the Capcoms for Apollo 13
Vance Brand (standing right) another Capcom for Apollo 13
In a healthy spacecraft, the CO2 meter should climb no higher than 2 or 3 millimeters of mercury. When it rose above 7, the crew was instructed to change their lithium hydroxide canisters. If it was allowed to rise above 15, the first signs of CO2 poisoning would set in.
Carbon Dioxide Threatens Astronauts
Lovell & Swigert work with temp hose connections. CO2 scrubber in background