What is the appropriate size HEPA filter used in a laminar hood?

The appropriate size HEPA filter used in a laminar hood is designed to capture a wide range of airborne particles, including bacteria and viruses. A HEPA filter is characterized by its capability to trap particles that are as small as 0.3 microns with an efficiency of 99.97%. While the size of the filter is an important factor, it is crucial to recognize that the standard HEPA filter size commonly used in laminar flow hoods is 0.22 microns. This size effectively ensures a sterile environment for compounding sterile preparations, which is essential in pharmacies to prevent contamination.

Filters that are larger, such as 0.45 microns, 1 micron, or 5 microns, do not meet the stringent requirements for the sterile processing of drugs and could allow harmful microorganisms to pass through, thereby increasing the risk of contamination in the compounding environment. Therefore, the correct size of HEPA filter for use in a laminar hood is indeed 0.22 microns, as it provides optimal filtration necessary for maintaining a clean and sterile working area.