I kind of look at it this way. Dude had to go somewhere to figure out how to build the coil, or someone built it for him and
they had to go somewhere to figure out how to build the coil. There have been plenty of news write ups on explosions by now, surely someone in his social circle has heard and mentioned to him, even if he hasn't. If I heard, or was told, that the device I was using had the chance of blowing up, I think I'd google it on my handy dandy smartphone. The first guy? He gets a pass, maybe even the second and third. But now? Uhm... yeah.