We are researching truly non-toxic ductwork for our all new electric heating/cooling… HVAC system. We are only finding the usual hardpipe which is known to be coated on inside with rust proofing, and the flex. The flex is found to be polyester and nylon in the interior with a wrap of insulation, probably but we’ve not been able to find that info yet, probably has fire retardant and formaldehyde, and who knows what. then the outer black plastic layer or silver whichever, silver would be best as all plastics outgas toxic fumes and when heated… even moreso. If someone could please point us to some truly non toxic ductwork… for a chemically sensitive person. Most normal people wouldn’t notice but all of us do, and must have all the toxic chemicals out of the line of fire, so to speak, as best we can. Thanks for any suggestions at all.