In clean room design, the anteroom must meet ISO class air quality.

• A. Anteroom
• B. Buffer room
• C. Main clean room
• D. Storage room

Answer: (A)

The transition space between less clean areas and the main controlled space is designed to control contaminants before they reach the cleanroom. That is why the anteroom must meet a defined ISO class—so when doors are opened or items pass through, particles are kept from migrating into the main cleanroom. This space acts as a buffer that helps maintain the cleanroom’s airflow pattern, pressure relationships, and overall cleanliness while personnel gown, move equipment, or transfer materials. By ensuring the anteroom itself meets the ISO class requirements, the integrity of the entire cleanroom system is preserved. The main cleanroom will have its own ISO class specification, while the storage or other non-interface rooms do not serve this boundary-control role.