Hi Steve, sorry to hear about the burn!
This happened to me early on with my #3 before I got the 3D. I was using very dry wood, the wood actually came from outside a grocery store used for smoking in a standard grill, not a smoker, it was VERY dry and before long, my temperature was higher than I had set it to and there was a lot of white smoke pumping out of the unit.
I have since learned several things, 1: Use quality chunks of wood, I highly recommend www.smokinlicious.com their moisture content is around 20%+ and burns slowly and will not catch fire like your son experienced. 2. If you are using a dryer wood then use a foil boat, wrap the wood up in foil or at least half wrap in foil so it won't catch fire. 3. If you don't already have one, get a chip screen to place in the bottom of your fire box, this also helped with my smokes. 4. You can place the wood in the back of the fire box, it seems that is the cooler spot of the element so that may help from starting the wood on fire.
I will say since I received my shipment of smokinlicious wood, I haven't had that issue at all anymore, that alone will probably solve the problem.
Hope that helps, there are others here that will also help out but the information I listed, I actually learned right here on this forum ;>)
Carl