How safe is hydrogen as a fuel?

09 October 2011

Question

I drive a car and I'm perfectly happy with the idea of driving around with a big tank of petrol underneath me, but for some reason, I'm slightly nervous about the idea of driving around with a big tank of hydrogen. For some reason, I just feel it could just explode! How safe are hydrogen driven cars or fuel cells compared to combustion engines?

Answer

Mark - This is obviously a very often asked question. The people who have looked at it really thoroughly conclude that it's about the same, if anything possibly a little bit safer, with the hydrogen. As we know, hydrogen is easier to ignite than petrol - but the thing is if you have a hydrogen leak, the hydrogen diffuses away so quickly that the hazard is very temporary. Conversely, if you have a leak of petrol, it's just going to sit there until someone cleans it up, and when it sets on fire, you have a fire blanket that covers everything and engulfs the car. Look up Michael Swain on the internet - there's a really nice comparison of a normal petrol car on fire and hydrogen car on fire, and you'll see that by the time the hydrogen is burned away, the car looks very much the same, whereas we've all seen on action films (or even in the street depending on where you live!) a burning normal car is very much not a car at the end of it.

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