How do I know if my rear derailleur is going to explode?

[velosam]

My chain snapped and bent both derailleurs.  I stripped everything and put it back.  I had to bend some bit of the bottom rear derailleur pulley but am concerned it's going to explode. How can I check its ok?


Also my new chain has not arrived but oddly enough the old one feels fine, is it safe to use until the new one arrives? ( I can't stand commuting on the winter bike!)

[Biggsy]

The derailleur is easy enough to check well enough by visual inspection, the chain not so easy.  I would not trust the chain again unless I knew the snap was caused by a bad join and had removed/fixed the link in question.  At least don't stand up on the pedals if you do risk it for one more ride.