The canary's suffering helped the crew discover a problem with the air purifier.
True. When Claribel fainted and was found unconscious by Sven, the crew initially did not understand the cause. However, when she revived briefly after receiving oxygen and then fainted again, the narrator realized that the canary's condition was a warning sign of air quality problems, similar to how miners used canaries to detect dangerous gases.
Explanation
The story confirms that Claribel's fainting spell alerted the crew to the air quality problem. The narrator remembers that 'miners used to carry canaries down to warn them of gas,' and this realization leads to the discovery that the air purifier had malfunctioned. Without Claribel's reaction, the crew would not have known about the danger until it was too late.