Hairdryer heaven

I was out of ideas and at the end of my tether this morning with both babies crying. It was raining hard, my back was hurting too much to lug the car seats around and my hair was still wet from my shower. Then I remembered the magic effect of the hairdryer. I sat on the bed with a baby lying on either side of me and dried my hair. They stopped crying immediately and E even fell asleep. Now all I need to know is how long can a hairdryer run for before it explodes?