hydrogen refinery would look same when on fire as when not. - except for the heat wave distortion, plumes of smoke from burning paint, drooping steel gangways, showers of electrical sparks from the shorting electrical system, and workers leaping from the upper levels.

And if the fuel in a hydrogen car decided to burn, everyone in its vicinity will find out in a real hurry - a fire that looks different is still a fire.

Though his point is valid - hydrogen will burn extremely quickly, we used to do these as demonstrations in school. Where a pool of gasoline will burn over a period of time, a tank full of hydrogen will burn almost instantaneously to disastrous effect - forget about rescue, the only sort of "rescue" will be body retrieval of whatever is left.

However, hydrogen will not pool like gasoline. If it doesn't ignite, it will just fly off into space. This mitigates some of the risk (i.e. if there is an accident, a fuel leak will either kill you quickly, or it won't)

so what youre telling me is that setting someone on fire with hydrogen is the perfect crime.

Or methanol (under the right circumstances): "Pure alcohols burn with a nearly invisible flame in daylight." (http://www.energyquest.ca.gov/transportation/alcohols.html)

Which was done in (yeah, I know) an episode of CSI:Miami: http://csimiami.wetpaint.com/page/207:Grand+Prix

Though, of course, hydrogen is far more exciting.

Indeed. I found the following amusing:

"There is actually more hydrogen in a liter of gasoline (116 grams) than there is in a liter of pure liquid hydrogen (71 grams)!"

But the coolest of all is that hydrogen flames are invisible! Hydrogen flames are so energetic that they emit UV radiation! I remember when I was in grade school and tried electrolysis at home. I managed to collect some hydrogen in a test tube, and I ignited it with a match. I heard a loud bang, but no flame. Sound, but no light. That was fascinating.