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Tim R[_2_] Tim R[_2_] is offline
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Default Diffferent techniques in troubleshooting

I'm a mechanical engineer but I've been in management a long time, I don't get to do much technical stuff.

This week I got called to a gas leak. The emergency response and the mechanics had already been there and confirmed safe to reoccupy, but somebody wasn't so sure and called me.

These things are 80% one problem and 9% the other. The crew that showed up found and fixed the 80% problem, but it wasn't actually causing the leak. The leak was somewhere else. Just because one thing is broken doesn't mean something else isn't broken too.

Once a problem is identified, attentional blindness sets in. Contrary evidence is not just ignored, it cannot be seen.

In this case the pilot light was out in the kitchen, and they assumed the gas smell came from it. They shut off the gas to the kitchen and authorized the building to be reoccupied.

They ignored the evidence the real leak was somewhere else - well, they were incapable of seeing that evidence because they already knew what was wrong.

When I got on scene it took little time to find where the smell was coming from. Partly that's from my bias to try to avoid assigning the cause until I've looked at all the evidence, but partly it's from knowing human nature and knowing if it were the usual problem they would have fixed it the first time, and it obviously wasn't.

I sent the mechanics back and told them where to look, and the second trip they fixed it correctly. Of course I had to keep quiet my part in it, there's always politics in these things.

So yes, fix the most likely fault first, but bear in mind the potential cost of it being something else.