Awful smell!

My dad has this neck thing, a heating pad I think its called, you heat it in the microwave.
The thing is, he heats it up for too long.
Your only supposed to heat it for 2 minutes, he sometimes leaves it in for four minutes.
The smell of it is horrendous, it smells like burn!
Today, he left it in even longer, until, boom!
It went off like a bom! Sparks were flying!
He tried to get it out of there but it was too hot to the touch!
Eventually he did get it out! Oh man!
I came into the kitchen with my laptop to sit and write, and that smell!
I dont know if a bomb smells when it goes off, but if it does, this sure smelled like burning and was just, awful.