Final answer:
CCR title 23 UST regulations dictate that monitoring equipment must be certified at installation and then regularly tested, although the exact frequency can vary and is typically outlined in the state-specific regulations.
Step-by-step explanation:
According to the CCR title 23 Underground Storage Tank (UST) regulations, the frequency for monitor certification varies depending on the state and the specific requirements that are laid out in the regulations. Generally speaking, monitoring equipment must be certified at installation and then regularly tested to ensure it operates correctly. The exact frequency of certification may be annual or set to a different specific interval. It's important to refer to the applicable state regulations or the UST technical compliance guidelines for precise requirements.