Zeolite-containing polyvinyl chloride containing compositions that are useful as the insulation for plenum cables are disclosed. A zeolite, either natural or synthetic, can satisfactorily replace either part or all of the molybdenum compound, particularly ammonium octamolybdate, in low smoke polyvinyl chloride based plenum compositions. Ion-exchanged zeolites, such as the zinc ion-exchanged zeolite can also be used. Zeolites are especially useful in lead-free Low Smoke PVC compositions. Because the cost of zeolite is only a fraction of the cost of the molybdenum compounds currently used in plenum cable compositions, this will dramatically reduce the cost of these materials.