Additional preparations are conducted on the day before release. (There should be three instruments on standby, i.e. checked and charged with solution at least three days earlier). The solution in the cathode and anode chambers is discarded, and the chambers are flushed and cleaned with de-ionized water, and then recharged. The sensor is connected to the bench tester and run on O3-free air for 10 minutes. While the instrument is running on O3-free air, the air flow is measured using the bubble apparatus and a stopwatch.