Methods are disclosed for filling a filter cartridge canister. Flow through an exit plenum and a filter screen of the canister is initially blocked, a sorbent inlet of the canister is open, and a ring of the canister is open. Flow is then initiated through the inlet and ring so sorbent particles and fluid flow into the canister. A pressure differential is provided between the inlet and the ring to enhance filling. The exit plenum is opened to impart an even fluid flow across a sorbent stratum. Flow through the ring is stopped, and sorbent particles continue to be added via the inlet until the cavity is filled. The filter screen is then compressed, the sorbent inlet is sealed and the filter screen is fixed to a compressed position while flow is maintained through the exit plenum.