Abstract: Fire-retardant, heat-resistant, smoke-suppressant plastic materials, such as polyvinyl chloride, having incorporated therein an intumescent material are disclosed. The intumescent material comprise and intumescent catalyst selected from the group consisting of salts of phosphoric acid and salts of sulfuric acid; and a carbonific material selected from the group consisting of starches, sugars, sugar alcohols, oils, and plasticizers. The fire-retardant, heat-resistant, smoke-suppressant plastic materials may be in the form of a foamed or non-foamed plastic. Methods of making such plastic materials are also disclosed.