PAT Testing Day!

Today was PAT testing day in the lab.  This is a peculiar British institution in which an electrician comes in to test all your portable appliances to make sure you don’t get electrocuted by them.  As an immigrant, I find this ritual a bit odd, because I spent my previous (American) life with untested portable appliances, and I (somehow) escaped electrocution.

The procedure involves testing the continuity of the earth (ground for Americans) conductor, then zapping the cable with a high voltage in the hope that this will detect any incipient failure of the insulation. [One hopes the high voltage doesn’t damage the equipment.] It costs the lab about £300, I think, and it takes some guy the better part of a day.

I was curious about whether or not this guy wastes his life in a vain attempt to save mine, so I looked up electrocution statistics for the UK for 2009-2010 [] There were just two fatal electrical accidents in the workplace in the UK that year, a surprisingly small number.  For a comparison against somewhere that doesn’t have PAT testing, let’s look at the USA: With a 5x larger population, there were 168 accidental workplace electrocutions per year [].    Correcting for the difference in population, a UK-sized chunk of the USA would have about 33 electrical fatalities.  Quite a few more.

Does that mean the PAT testing man is really being helpful?   Probably, though it’s hard to say how much.   Mostly, that’s because only a fraction of electrical fatalities involve problems with electrical cords and plugs.  Construction workers sometimes accidentally work on a “hot” circuit, people sometimes drive cranes into power lines, and other things, too.  So, while the PAT testing man and his safety-related kin are saving about 30 lives per year, probably most of the saves aren’t due to PAT tests.

Of course, those lives saved come at a cost.  The ten (or so) of us in lab seem to employ a PAT guy for about a half of a day per year.  If I extrapolate to all of the UK, there must be about
30 million workers * (0.5 PAT man-days per year / 10 equipment-user-man-years per year)
which works out to about 7500 full-time PAT testers in the UK.  So, if we want to compute how many people an average PAT tester saves in a lifetime, we do this:
50 years-of-work * 20 lives-saved-per-year / 7500 PAT-testers,
which is just 0.13 person.  Hmm.  I’m not sure I’d be entirely happy being a PAT tester.   Spend 7.5 lifetimes to save one life?   I suppose it could be worse, though.   [This is a very rough guess, because there are a lot of factors being ignored.  For instance, we may have more equipment than the average British worker.   So, it might not be fair to extrapolate from us to the UK economy.   There may be fewer than 7500 PAT test guys, and therefore there may be more saves per person.  On the other hand, not all the 20 saves are from PAT testing…]

Financially, it looks like PAT testing costs about
7500 PAT-testers * about 30,000 pounds-per-year = 225 million pounds,
which is quite a lot of money: about 10 million pounds per life saved.  Probably, PAT testing is not the best way to save lives.  For instance, that money would pay for an awful lot of medical care or medical research. [We also spend some time disconnecting and reconnecting equipment and making him a cup of tea, all of which is lost productivity in addition to the direct cost.  So the total cost is somewhat larger than this figure.  But also see above: lots of uncertainties.]

One of the odd wrinkles in the regulation is that it doesn’t apply to everything, only equipment that is easy to move or intended to move when connected to the power line.  Somehow, this gets translated into the electrician unplugging the electrical cord from a computer — unplugging it both from the wall socket and from the computer — and then testing the disconnected cord.  I think the computer doesn’t have to get tested because it “has a mass exceeding 18kg and is not provided with a carrying handle” [] but the power cord itself is portable.  Watching this process may be the visual equivalent of a Zen koan.

My bet is that PAT testing is a living fossil from the 1960s, when everyone put their own plugs on their electrical equipment, and half of them were done badly.   And, back then, cotton cloth was used to insulate electrical cords, rather than modern tough plastics.  I’ll bet PAT testing saved a lot more lives in the 1960s (if my guess is correct).  I rather think the advance of technology, specifically moulded plastic plugs, has made it largely obsolete.

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