If there's blood, I think it's fair to say they should have gone off. I'd have those airbags checked and possibly replaced.

> They’re primarily intended to provide some protection for unbelted passengers

I don't think they're meant for unbelted passengers; they should be belted first. I once saw a program about the difference between regular airbags and airbags designed to be used without a seatbelt, and the latter were enormous monstrosities that could knock you out. They were determined to be a bad idea. (I wish I knew where I saw this, but it was decades ago and I don't.)