I used to work in the petroleum field and my suggestion would be you need to consult a specialist. It may be a zone 2 area but unless the hearing aid is atex rated then there is the potential for ignition. A specilaist will provide guidance on this. Try the Association for Petroleum and Explosives Administration, they may be able to provide contacts. Not sure if you can get atex rated hearing aids and it may be that the HASAW overrides DDA in this area and that the employee can no longer work in zoned areas.

If it is a conventional and modern hearing aid without a power on-off switch with contacts that directly interrupt battery current, then ATEX is not an issue. Typically, this type of device is classed as a PEP 1 device and can be used within the ZONE 2 area without risk of ignition and without requiring an ATEX or CE mark. PEP 1: body worn portable electronic product, in direct contact with the skin, that is deemed incapable of causing an ignition under normal conditions. PEP shall meet the following criteria: a) Radio frequency energy transmission limited in accordance with 8.3 b) No provisions for forced ventilation c) No sparks visible in normal operation d) No excessive temperatures in normal operation e) No camera flash unless it can be mechanically disabled f) No motors unless it can be demonstrated the motor incorporates non-arcing technology g) No visible damage h) No available listed apparatus suitable for the area classification and capable of performing the intended function PEP 1 Products meeting the general criteria in 6.1 and all of the following additional criteria may be designated as PEP 1: a) Powered by a maximum of two button cells b) Body-worn and in direct contact with the skin c) No electrical connections accessible outside the product Examples are electronic wris[expletive deleted]ches and hearing aids that are inserted into the ears.

Thanks all for the welcome advice. Much appreciated.