Posted By David Scott Nick, We asked the very same question of the HSE some 7/8 years ago via our trade organisation BAMA and the reply was as follows; 'There are, as far as I am aware, no electronic wris[expletive deleted]ches commonly available which have been formally approved for use in hazardous areas ie Zoned areas where explosive or flammable atmospheres may be present. Some years ago ignition tets were carried out on typical wris[expletive deleted]ches. The findings suggested that generally speaking there was no risk of ignition but under particular circumstances ignition was possible. A risk of ignition exists if lithium batteries of 3 volts (or more) are used or the watch casing becomes broken so exposing the backlighting filament to a carbon disulphide mixture. Electronic wris[expletive deleted]ches using a nominal 1.5 volts battery worn in less sensitive mixtures than CS2 are not considered to pose a risk'. This was signed by a D Pumford of the then Electrical&Control Systems Group of the HSE! As for hearing aids, you can actually get intrinsically safe variations and you need to talk to your local audiometry department within the NHS. I have just had one employee supplied with two units, 1 for each ear of course, free of charge. That said, if the type required cannot be supplied as an intrinically safe varient then risk assess and write down your decisions using the logic from above. Hope that this helps. As a matter of interest, I use a hearing aid which cannot be supplied as intrinsically safe in a LPG environment.