Volume Compensators are used for a vapor canister which includes a partition adapted to be disposed in an interior chamber of the vapor canister and having a single opening extending. The volume compensator assembly also includes a grid pattern disposed on the partition about the opening to guide airflow to the opening. This assembly includes a spring connected to the partition and contacting the vapor canister to move the partition for compensation of a volume of a bed of vapor adsorbing material in the vapor canister.