Can I draw your attention to an article in Spring Issue of Switchedon, published by the Electrical Safety Council.
It warns of the danger of the usual plug-top charger, that you find everywhere these days. They tested ten samples obtained from various suppliers, and found that all ten failed the safety tests
The article says that 1.8 million were bought in the UK last year, and they are produced in Hong Kong for 3p each!
If you have bought any of these,particularly if they are to be used in medical locations, you might not get what you expected.
It seems that even CE marked devices can be dangerous!

Hi Bam

Can you elaborate on the problem/s they found?

btw - I've heard the referred to as "wall warts" partucularly by guitarists!

Mick

Unfortunately the article is not available on the web, only in print, which is not helpful
It states that 3600 chargers have been seized from retailers over a 6 - 8 week period.
It was found that typically there was insufficient insulation between live parts and between input/output circuits
This could result in the output reaching mains voltage.
A number of other faults were found, and it is suggested that you should not assume that because the device is CE Marked it is safe to use, due to lack of control over CE Marking.
There is a similar article on the MHRA web site, to find it go to www.mhra.gov.uk then type "switch-mode" into the search box in the top right hand corner.

One big problem is the IET code of practice for PAT testing non-medical devices only indicates to conduct visual checks on class II devices. This means no routine safety testing is conducted so we have no idea how big the problem is.

Even if the COP was changed, another problem is that most of those involved in PAT testing don't know how to test these devices properly.

They think wrapping some foil around the plastic case and conducting an insulation test between the mains pins and the foil is a good test!

They never think that the user will touch the metal (low voltage) output plug or metal chassis of the laptop it connects to and therefore it might be a good idea to test the insulation between the AC pins and output pins! (Ideally using an AC leakage test and not a DC test to ensure you get a true idea of the potential leakage.)

First of all (and as I have said before) ... forget (that is, ignore) CE marking. In practical terms, it means nothing. You can buy rolls of CE stickers, and stick them on yourself if you want.

Secondly, yes ... "wall warts" are junk, electrically (safety) speaking. But, who is at risk here? The patient? I don't think so. The user then? Yes, perhaps.

But (unless I've lost the plot, and failed to keep up ... both of which are quite likely), I believe that the stringent low values of allowable leakage currents applicable to the various classes of medical equipment (with which we are all familiar) are there to protect patients in electrically compromised situations (that is, when natural defences have been breached), as when in direct electrical contact (for purposes of examination or therapy), or when undergoing surgery, with electrodes poking about within the body, in an anaethetised state, etc., etc.

So let's not get too excited about the 3p "charger" ("adapter", whatever). What are you going to do ...bin them all? [yes ... good idea]

And ... what about all the clearly "non-medical" ones seen every day in any hospital? All the "personal stuff" ... like mobile device chargers and all the rest? How about going around and cropping the leads off just where they exit the "charger". H'mmm. That should get the owner's attention!

Not being one to "disrespect" the NHS (for example) ... surely hospitals have some sort of policy about all this?

Personally, if I was doing the rounds on an electrical safety mission, I would assess each bit of kit as I found it. My reaction would depend upon where the thing was, what its purpose was, and what else was supposed to be going on there. If it was owned by someone other than the hospital (and I thought it presented some sort of risk), I would "have words" with the owner. If it was something outrageous, I would destroy the thing and chuck it in the bin. How's that for a Policy Guideline?

Like the Retailers (and worms like Estate Agents) like to say, it's all about "Location, Location" ... and, er "Location".

One last thought ... if the laptop (etc.) user is happy enough to accept the "risk" (or, more likely, crack on in blissful ignorance) of using the laptop (etc.) at home, with all the attendant "accidents waiting to happen" there (spilled coffee comes to mind) ... need we make a fuss about the same equipment being used in the hospital? Well, unfortunately, yes ... "duty of care" and all that. And third parties (injured parties, even) are likely to be involved. So ... surely we (the management, someone) has the right to require that no unsafe junk be brought within the hospital from outside.

Again ...location:- office environments :: OK. "Medical" environments (define) :: keep the junk out. Discuss (actually, it's an important issue) ... similar to the perennial "extension lead" problem!

Some good points there, Geoff. I think at least some of the issue comes down to successful education. I have had, over the years, quite senior medical people basically saying 'what's wrong with that, it's OK at home'? My reply has usually been along the lines of 'true, but when was the last time you carried out major invasive surgery at home on your kitchen table'? Of course, they commented that it would be a totally inappropriate environment (for 1st world locations at least), to which I said 'and so this hospital environment is inappropriate for this 'home' electrical device'! It seemed to get the point home!

Of course in developing countries such as where I am now, it's difficult (and perhaps counter-productive) to be quite so strict. Sometimes of course, the environment is so 'bad', that it's even MORE important to be strict about certain patient-safety issues. Surely, that's what part of our profession is about; knowing what really IS important in any particular situation, with often conflicting needs existing simultaneously?!

People who make the rules might like to think about colour coding.

You know, have "home use" equipment painted Day-Glo Orange ... then ban such devices from entering specific areas of the hospital ... on pain of meeting the guy with the side cutters!

Another "solution" could be yet another stick on label:-

Not for use in Patient Areas

... or some such thing (again, on pain of seeing it ... er, taken away)!

So ... when doing the rounds, if you come across objectionable kit that lacks your regular asset/PM/green dot/date (whatever) sticker, or no label like that above ... it's "Heigh-Ho, Heigh-Ho ... and in the Bin We Go"!

By the way, what is the allowable insulation and leakage criteria for these things (both in the home ... and in the "patient ennvironment" where applicable and/or necessary)?

Let's have Chapter and Verse (which Standard, what figures, how should we test - if at all), please.

And (here's a teaser for you all whilst I'm out) ... if such junk has to be used in, say, the operating theatre ... would plugging them in to a medical isolation transformer render them "safe"?

I don't think that the actual leakage current on some of the chargers tested matters too much, in many cases the output voltage was at about the mains input voltage, since the only separation between the input and output was the enamel on the copper wire!
You would expect the leakage current on a 60601 compatible charger to be less than 10 microamps, but if you cannot trust the CE Marking, you might just as well buy the cheapest available.
To test the charger I would suggest that you plug it in to the normal mains supply, and then measure the voltage between earth and either side of the output using an autoranging DMM. In most cases the output voltage will be less than 12 volts DC, so it does not matter which side of the output you measure.If the meter reads 100 volts or more, then stop there, but if you are getting a reading of just a few volts, then it should be safe to switch the meter to the AC current range. If there is any likelihood of the patient that is using the device being supplied by the charger having a catheter inserted into the central circulatory system, then anything greater than 10 microamps would be dangerous.
It would not really help to use an isolation transformer. If you measure the current between either side of the transformer secondary and earth you will find that it is much more than 10 microamps!

Who is the Electrical Safety Council? What weight do their recommendations have?


What tests were these, I wonder?


Do they say what what they regard as an acceptable figure for insulation?

It sounds to me like we're actually talking about macro shock (rather than patient related micro shock) hazards here. Just as (potentially) deadly, of course, but dare I suggest that a different set of "duties of care" may apply?

Surely the Bottom Line here is to (whilst forgetting about CE marks) only permit chargers (adaptors ... call them what you will) with certified 60601 approval into any "medical area"?