Determines CO2 evolution to assess biodegradability by soil and sewerage micro-organisms. Shake flask fits standard laboratory shakers. #7 Ace-Thred side port with Nylon bushing and FETFE O-ring holds a glass septum adapter. Inner well has a capacity of 10 mL plus head space. Well is held securely in Ace-Thred with nylon bushing and FETFE o-ring that permits variable depth positioning. Well top is flared to accept septum and can be removed or pierced to permit venting for aerating of culture media.