Air supply to the sterile area must be appropriately filtered to minimize the potential contamination by both viable and nonviable particulate matter. HEPA filters are used to filter the air, both at terminal points of blowers and in Laminar Air Flow Hood where product will be exposed. The HEPA Filter fixtures are to be monitored periodically by the following tests to check that they maintain their rated efficiency.
In addition to monitoring the filter surface, the seal of each filter element to its frame and the seal between the filter frame and the filter housing must be monitored to verify that particles are not escaping around the filter.
Air velocity of laminar flow hoods is measured to assure an acceptable level of airflow in the sterile area, solution preparation area.
In case of Laminar Air Flow hoods, measure the air velocity by positioning the velometer probe at a distance of one foot above the work surface. Read the air flow directly form the meter and record. Six readings should be taken and the average calculated.
In case of Terminal HEPA filters, the velocity should be taken six inches away from the grill and six readings should be taken and averaged and these readings should be taken for calculating air changes in the room.
A minimum acceptable air velocity for vertical Laminar Air Flow hoods is 0.3 meters/second (60.0 ft/minute). Similarly minimum acceptable velocity for horizontal Laminar Air Flow hoods is 0.45 meters/second (88.5 ft/minutes)
* If velocity drops below the acceptable criteria, replace the filters
Frequency of Test: Quarterly