The filter on your scrubber canister can get worn out over time, considering your scrubber is what prevents you from breathing CO2 rather than O2, it is a good idea to make sure your filter is in tact before diving. If it is not, this kit will do the trick!
While there's no hard and fast rule on replacing these filters, they should be checked when you assemble your Poseidon Rebreather.
Customers using the Tecme Self-Pack Canister for the SE7EN will need two of these kits to complete a filter replacement.