Yeah, I guess in the event of a problem, there'd be lots of nasty fumes around the launch complex.
Ah, the announcer just explained that they make that announcement every time, and I've just never heard it before.
I hope Amy's parents are enjoying their visit to KSC today. :-) They're still more or less expecting to launch, despite the sensor malfunction. I suspect they'll make a final decision later; the consensus seems to be that they can fly without that sensor working.