Specifies a method for the determination of compressive creep of rigid cellular plastics under specified conditions of load, temperature, relative humidity and time. Test specimes in form or rectangular parallelepipeds are placed between two flat plates and the specified load is applied as follows: procedure A) at standard conditions and procedure B) at agreed conditions of temperture and time. The difference in compressive deformation of the loaded specimen at standard atmospheric conditions and at elevated temperature after specified time shall be calculated.