Abstract: An insulated conductor and the flame retardant insulation composition used in plenum cables. The insulation composition includes as a polyolefin blend from about 50 to 85 parts by weight of polypropylene, 10 to about 40 parts by weight of a very low density polyethylene and from about 5 to about 20 parts by weight of a high and/or low density polyethylene. To one hundred parts by weight of the polyolefin blend there is about 6 to about 20 parts by weight of a chlorinated flame retardant, from about 4 to about 12 parts by weight of a flame retardant intumescent, from about 20 to 60 parts by weight of a non-halogen flame retardant, from about 0.2 to about 1.0 parts by weight of hindered phenolic stabilizer; and from about 0.1 to about 0.4 parts by weight of additional stabilizers. One of the non-halogen flame retardants in the polyolefin composition, may be zinc borate which triggers polymer and flame retardant decomposition when the polyolefin composition is exposed to an igniting flame.