How often should a prefilter in a laminar airflow hood be cleaned or changed?

A prefilter in a laminar airflow hood should typically be cleaned or changed every 1 to 3 months, depending on usage and the specific environment. Frequent use or high levels of particulate matter can necessitate more regular maintenance. It's essential to monitor the prefilter for visible dirt or a decrease in airflow performance, which may indicate the need for cleaning or replacement. Always follow the manufacturer's guidelines for specific recommendations.