The efficiency rating of HEPA filters is 99.995%, making them a popular choice for air filtration. However, ULPA filters trap more and smaller particles than HEPA filters, with an efficiency rating of 99.999% at removing submicron particles 0.12 microns in diameter or greater. HEPA filters are 99.97% efficient at removing particles 0.3 microns in diameter or greater. To increase their effectiveness, HEPA filters can be combined with pre-filters to trap larger particles before they come into contact with the main filter. The MERV rating system is used to measure the effectiveness of air filters, with HEPA filters being at the highest level.
These filters remove more pollutants from the air than HEPA filters, requiring 99.99% efficiency with a target particle size of 0.1 micron. ULPA filters are designed similarly to HEPA filters, but feature a denser network of randomly arranged fibers. HEPA and ULPA filters are used in a variety of applications, such as industrial vacuums to remove asbestos, remove toner dust from office equipment, prevent the spread of bacteria in operating rooms, and other medical air filtration applications. However, designing a ULPA system to deliver the same ACH as a HEPA system would require a larger filter to compensate for the more restrictive flow and, possibly, a more powerful blower, making the entire filter system larger and more expensive. HEPA filters have a lifespan of up to ten years, while ULPA filters typically last between five to eight years. This reduction is due to the fact that the air first passes through the HEPA filter and goes through the UV-C process.
Additionally, pre-filters are often used to protect the finer filters downstream, so additional pre-filtration may be necessary to protect the ULPA filter. When searching for air filters, you may come across one that claims to be a true HEPA filter. It is important to understand your application requirements and the level of efficiency required in order to choose the right air filter for your needs. An ULPA air filter may look better on paper because it reduces particles of smaller sizes and larger particles; however, a filtration system designed for a certain airflow must be designed to anticipate the resistance of the filter element to flow, and an ULPA filter would be too restrictive in a system designed for HEPA.