Both Liquid Bottles and Gas Canisters can be "Emptied", dumping the contents into the surrounding environment. While this generates a chore, it does not enable the priority overlay like "sweep" will.
If you set a container to both "Sweep" and "Empty", you will be able to set the priority of the "Empty" task
1. Mark an Oxygen canister for "Empty" 2. Note the lack of a priority overlay. 3. Mark the canister for sweeping. 4. Change the priority from 5 5. Unmark the canister for sweeping 6. Note the priority on the generated "Empty Storage" chore.