HEPA and ULPA Filters: Advantages, Limitations, and HVAC System Considerations
Choosing the wrong air filter can compromise regulatory compliance and indoor air quality (IAQ). Some facilities require more specialized air filtration than what MERV filters can provide. Industries such as pharmaceuticals, aerospace, and other critical environments need to ensure airborne contaminants are kept to a minimum. Both HEPA (High Efficiency Particulate Air) and ULPA (Ultra Low Particulate Air) filters can be suited to the task, but they are not the same thing.
High-Efficiency Rated Filters Versus MERV
Both HEPA and ULPA filters feature thicker media compared to MERV-rated pleated filters. HEPA filters are designed to remove a minimum of 99.97% of particulate matter 0.3 micron or larger in diameter. ULPA filters are denser than HEPAs and target a smaller particulate range, with a minimum capture efficiency of 99.9995% for particles 0.12 micron or larger. Both types of filters are generally sealed with a self-repairing gel. Both HEPA and ULPA filters capture particles in the same way as MERV-rated filters in HVAC systems, but their thicker, finer media can risk causing a resistance to airflow called pressure drop (discussed later).
It is critical to note HEPA and ULPA filters are not suitable for removing volatile organic compounds (VOCs), gases, chemical contaminants, or odors. Carbon filters are built for these jobs, working through chemical adsorption rather than particulate capture. Facilities requiring comprehensive IAQ control to address gaseous contaminants may find it helpful to explore carbon filtration's role in IAQ.
Challenges with High-Level Filtration
While HEPA and ULPA filters are engineered for optimal performance in critical environments, they are not without potential issues. Addressing these challenges requires careful planning and system assessment.
· Extending HEPA and ULPA Usability with Pre-filtration
o The fine media in HEPA filters and the superfine media in ULPA filters clog faster than other pleated filters, which shortens their lifespan.
o Pre-filtration can be used to improve performance and extend the lifespan of these filters.
o Pre-filtration involves installing a lower-rated filter, such as a MERV 8 filter, upstream from the HEPA or ULPA filter.
o Pre-filtration captures larger particles before they reach the high-efficiency filters, keeping the HEPA and ULPA filters free to capture the smaller particles they are designed for, and helps the HVAC system run more smoothly.
· The Problem of Pressure Drop and System Strain
o Pressure drop is a critical issue that can occur because HEPA and ULPA filters are thicker with finer media than standard MERV-rated filters. This makes them naturally more resistant to the flow of air and can restrict or block airflow.
o Implementing high-efficiency filters may present a challenge for smaller HVAC systems. They may not be equipped with motors and blowers strong enough to overcome this resistance. The system must be capable of producing sufficient airflow to compensate for the denser media.
o Pressure drop leads to increased energy consumption when the HVAC system must work harder to force air through the filters. Due to the combined effects of resistance and size, ULPA filters are not suitable for some HVAC systems designed for lower static pressure. The increased size of HEPA over MERV filters combined with pressure drop may render them incompatible with some compact systems.
· Preventing Bypass Leaks
o Air bypass happens when some system air flows around the filter, rather than through it.
o This issue is caused by filters that are improperly installed, damaged, or of the wrong size, or when filters become clogged quickly and are not changed regularly.
o Bypass leaks force unfiltered air through the HVAC system and directly into the critical environment.
o Because an improperly installed, sized, or damaged filter can severely impact performance and lead to costly strains on the system, it is imperative a qualified professional assess the system and facility's requirements before HEPA or ULPA filters are deployed.
How ATL Filtration™ Can Help
Choosing between HEPA and ULPA filters is dependent on the requirements of your critical environment, and professional guidance is imperative. The NAFA Certified Air Filter Specialists (CAFS) at ATL Filtration™ have the knowledge and experience to not only ensure you use the correct high-efficiency filters but also to integrate necessary solutions to extend filter lifespan and smooth HVAC system operation. We ensure your facility remains compliant with local regulations while mitigating risks like costly system overwork. Book a free consultation through our Aire Assist program today to protect your HVAC investment, improve performance, and optimize your critical environment's air quality.