How safe are the MQ- Gas sensors?

I've been reading these things run HOT!

Would it be a good idea to have multiple MQ- type gas sensors of different kinds all in row of each-other on a wrist watch?

I read they run at 500c just one of them alone could melt your skin off if there is a short or an electrical issue some where?

Am i just over thinking this or are these things safe to run as a wrist watch?

just one of them alone could melt your skin off

No, skin doesn't melt, it will only char and then bust into flames.

What you need to find out is how hot these things are on the outside not the inside. See the data sheet for this sort of information.