Moshe, The answer to your question is Reinforced insulation for the working voltage measured in that location.
The 72V supply is considered hazardous voltage and if an SELV circuit is present on conductors nearby, this is the type of insulation system that is required. If this "CO like" enviroment can be considered a "Restricted Access Area" per 2.1.4.2 (EN60950), or "Service Access Area" per 2.1.4.1, lesser requirements may apply. Also consider if this "SELV" circuit does not need to be classified as SELV (no operator access), you may be able to get away with no insulation, but other requirements may apply depending on how this system is set-up. Regards, Edward Eszlari TUV Rheinland of N.A., Inc. Marlborough, MA 508-460-0792
