Abstract: A foam body structure formed of plastic foam with one or more flame retardant reception cavities formed in the main body either simultaneously with an initial foam body formation process such as expandable plastic bead molding or subsequent to the foam body formation such as by melting, drilling or cutting. A solid flame retardant such as one in granular form is preferably supplied in sufficient quantity as to entirely fill the volume defined by the reception cavities. A covering or coating is provided over the flame retardant material to fix the material within the cavities. The volume and distribution of the reception cavities and the amount of the chosen flame retardant received in the cavities is sufficient to provide an essentially common flame retardation quality or characteristic over the entire volume of foam body (or at least the volume that could be exposed to a flame in its intended use).