While the astronauts appear to have enough oxygen to keep them alive, one thing they have too much of is carbon dioxide.
9 seconds sound clip from the Apollo 13 movie soundboard.
You can hear this line at 01:29:45 in the Blu-ray version of the movie.
Quote context
[...]
- Now, wait a second. That's not what he said. He said we're working on it.
- You want to cut the duct tape three feet long. Just use your arm. It's an arm's length.
- Okay, Housotn, I see what you're getting at. Hold on.
- Hey, Jack, tear that piece of tape down the middle lengthwise.
- Houston, what do we do if we ripped the bag? Can we tape it?
- Oh, no.
- Stand by. What should I tell them to do?
[...]