Final answer:
The frequency of HEPA filter testing depends on the setting and use, but is generally conducted annually to ensure efficacy and performance.
Step-by-step explanation:
A HEPA filter, which stands for high-efficiency particulate air filter, is designed to capture a wide range of particles, including bacterial cells, endospores, and viruses, as air flows through it. The frequency at which a HEPA filter should be tested to ensure its effectiveness is not specifically spelled out in the provided reference material. However, in many professional environments, HEPA filters are generally checked on an annual basis to maintain performance standards. This is especially critical in settings such as hospitals, laboratories, and manufacturing facilities, where air quality is of paramount importance. While certain settings may require more frequent testing depending on regulations or operational conditions, if you have to choose between the given options without further context, an annual check would be a reasonable answer.