The more pure the oxygen, the more explosive it is if I remember my science class.  I empathize with anyone who has emphysema, for there is no cure..it gets progressively worse. and eventually kills. I suppose some might think he just fired up a heater and thought nothing would happen. My feeling is if he just had a treatment, often times too much or too little oxygen can among other things, cause confusion. If that were the case, he might have forgotten the fact the tanks were in the van. Another possible is the "fight or flight" syndrome. He could have run out of oxygen when he needed it. Panic sets in (fight or flight) and could have been on his way to the hospital to get emergency. Why light up then you might ask? Oddly enough, a few puffs off a smoke can temporarily ease both the breathing and the panic.

 

An 82-year-old New Jersey homeless man with emphysema inadvertently caused an explosive car accident after his cigarette ignited gas leaking from at least one of the seven oxygen tanks stashed inside his car.

But the saying “smoking kills” doesn’t apply to this lucky man, who escaped with only superficial injuries.

Hackensack Fire Chief Matt Wagner said the unidentified man uses a tank of oxygen every day and regularly stores his tank, along with his other possessions, inside his vehicle.

via Smoke, bomb - WWW.THEDAILY.COM.