Earlier quoted context omitted.
In such a case the crew would be dead whatever they did. Even if we assume there were enough suits for everyone to evacuate the Shuttle through the hatch (which AFAIK there weren't), and that people were able to evacuate before the fire caught them (which is unlikely), they would still be stuck in orbit with suits having only enough air for a few hours (the length of an ordinary EVA) and no way to get back to Earth.
Both of us are reasoning from a lack of access to shuttle schematics, but I'm always hesitant to say "never." I was thinking of a fire that incapacitated the commander, was spreading, and the best available option was immediately venting all oxygen in the shuttle (probably with some crew loss of life), in order to potentially save enough systems to return home. On the one hand, that's an extremely far-fetched scenari…
If you're referring to Apollo 1, that event drove comprehensive changes to the Apollo design to ensure that it wouldn't happen again. And it didn't.
If you're referring to Challenger and Columbia, I'm not sure what "means to save themselves" you are referring to.