Abstract: A coaxial-type heater cable is described for significantly reducing both electromagnetic and electrostatic field while maintaining a flexible heater cable structure by enclosing coaxial arranged inner and outer conductors with a conductive polymer layer that is in electrical contract with the outer conductor. The outer conductor is helically wrapped around the inner conductor with the number of turns per unit length selected to significantly reduce the electromagnetic field emanating from the heater cable while the conductive polymer layer significantly attenuates any electrostatic field that would otherwise fringe through spaces between successive turns of the outer conductor. The heater cable can be of the self-regulating type using a PTC material in electrical contact with and between the inner and outer conductors.

Abstract: A self-temperature regulating heater cable using a PTC polymeric matrix is described. A commercially available low density polyethylene is combined with a desired carbon black so as to enable a continuous extrusion at an elevated temperature while enabling residual heat in the extruded PTC layer to anneal the layer to a desired low resistivity in a short time period before quenching. The polyethylene is of the DFD-6005 type in which the amount of molecules whose molecular weight does not exceed about 23,000 is less than about eight percent by weight. The carbon black preferably is a low structure, low resistivity, non-surface treated, conductive carbon black.

Abstract: A heated comfort product such as an electrical blanket having an elongate electrical resistance element is connected in a particular manner to an AC power line by connecting the ends of conductors used in the element at a common end to respective AC power lines so as to achieve reduced or non-detectable electromagnetic and/or electrostatic radiating fields from the comfort product.