Posted By Martin J Morley HSE have just put out guidance about the safe use of these trolleys. See http://www.hse.gov.uk/se...ucation/safety121009.htm for the 'full' details. So what is there inside these trolleys that is so dangerous? I used to work with studio electronic flash units with 5000 joules of capacitance, without any incidents from the power packs. I had assumed, possibly as some of the manufacturers also had, that these trolleys were merely extension leads on wheels. This incident and the HSE warning suggest something more complex - but how does just switching off the socket prevent a possible incident? They say that an investigation was carried out into an electric shock incident involving a laptop charging trolley that had been presumed to be a static discharge, but was strong enough to hospitalize the teacher. This investigation apparently found there was "sufficient stored electric charge on the pins of the plug to give the user an electric shock." The key recommendation seems to be that the socket should be switched off before removing the plug, but the quote above suggests that there is still the possibility of danger. If there is capacitance, then surely the units need rebuilding to ensure adequate discharge? Are there any electronics expert out there who can shed some light on this? martin

Posted By Bob Howden A similar (or the same) accident is covered in a RoSPA e-bulletin for the education sector. It provides a little more information about the incident and subsequent investigation. Found it just be doing a simple search on Google.