Untrue about the accident. It only produces enough HHO to be in the transfer tube and if applicable, the bubbler.
I did a little experiment with mine, I held a lighter to the end of the HHO tube when it was on, it popped, and the top came off (the pressure release valve), but no explosion...no detonation...nothing.
Until I'm proved otherwise, HHO will not be deadly in an accident.
And steve, I've yet to see a car blow up around 10 city blocks...and I'm in the fire service, so I've seen a few car fires
I actually have seen 1 car blow, and it had a propane tank in the back and it wasn't even on duty...it was pretty neat though.
But don't be too worried...your worse off to have an oxygen cylinder (which people drive around with all the time) in the trunk, or a propane tank for a BBQ. Or even 5 gallons of gas sitting in the bed....so don't be too worried about HHO. You might melt your paint on your hood a little, or cause a single vehicle fire, but it's going to be nothing seriuos...and after all, there is water in the device :)