The term HEPA filter has been loosely used as a term for most secondary and final filters for many years. Although this in itself is not a big deal, the fact that many facilities believe they have HEPA filters when they actually don’t, is a bit alarming!

The first step in this issue, is to know either what is required by the regulating body in your industry or what you are trying to achieve. Then reach out to a professional that can help identify what filters you have or what you need.

True HEPA filters are typically identifiable by a rating on the filter that says it is a 99.97% efficient or higher and will not have a MERV rating listed on the tag. If the filter is a 98% or lower, it is not considered a HEPA. Normally HEPA filters would have a face gasket of of either a foam rubber or a gel material in a track that a knife edge imbeds into for a air tight seal. HEPA filters also would typically have 2 layers of prefilters ahead of them, for example a MERV 10 pleated filter and then a MERV 14 bag or box filter with the HEPA filter last in line.

Using a HEPA where the system was not designed for one can be very problematic due to the back pressure created by these filters. This could severely impact the airflow of your HVAC system causing a host of issues from the unit freezing up creating service issues to a substantial reduction in air changes creating further IAQ issues. If you are trying to improve your facility filtration, it is advised that a engineer or a filtration specialist be involved in laying out a plan that takes everything into consideration.

Not using a HEPA where one has been designed in a system is not a problem for the HVAC system, but if your areas fed by the unit are dependent on high purity filtration, you may experience contamination issues or compliance failures if its an inspected facility.

To summarize:

• A HEPA Filter will have a tag on it that states its a 99.97% efficient or higher.
• It will have a gasket to achieve an airtight seal.
• It will not likely have a MERV rating on the tag.
• A HEPA filter will likely have 2 stages of filtration before it.