How big should a ceiling access panel be ?

Update:Aug 15,2023
Summary:If your access panel will grant personnel entry – in other words, if a human being will need to crawl partially or completely through the opening – it......
If your access panel will grant personnel entry – in other words, if a human being will need to crawl partially or completely through the opening – it must be at least 20 by 20 inches. If this is not possible, it should be large enough for cleaning and spaced at 12-foot intervals throughout the space.