This International Standard specifies a method of determining: a) the compressive strength and corresponding relative deformation, or b) the compressive stress at 10 % relative deformation, and c) when desired, the compressive modulus of rigid cellular plastics. There are two procedures: — Procedure A employs crosshead motion for determination of compressive properties. Procedure A is intended to be used when compressive stress at 10 % relative deformation has to be determined. — Procedure B employs strain measuring devices mounted on the specimen (contact extensometer) or similar device which measures directly sample deformation. Procedure B is intended to be used when compressive modulus has to be determined. NOTE Compressive strength (at maximum load) can be determined either with Procedure A and B.