Which of the following is not considered a confined space?

• A. Manhole
• B. Anaerobic digester
• C. Lift station wet well
• D. Operator control room

Answer: (D)

Operator control room is not a confined space. Confined spaces are places with limited entry and exit and not designed for continuous occupancy, often with poor ventilation and potentially hazardous atmospheres. A manhole has a small opening, restricted air movement, and limited egress, making it a confined space. An anaerobic digester is a large enclosed tank where gases can accumulate and entry is restricted, so it also fits. A lift station wet well is an underground chamber with restricted access and possible hazardous atmospheres, qualifying as a confined space. The control room, on the other hand, is designed for ongoing occupancy, with good ventilation and easy entry/exit, so it does not meet the criteria for a confined space.