ULPAfilters

ULPA filters, short for Ultra-Low Penetration Air filters, are high-efficiency air filtration devices designed to capture a very large fraction of submicron particles. In standardized testing, ULPA filters typically remove at least 99.999% of particles around 0.12 micrometers in diameter, placing them beyond standard HEPA performance for most applications. They are commonly classified into U15, U16, and U17 classes under ISO 29463/EN 1822, with higher classes indicating greater efficiency at the most penetrating particle size.

Construction and operation aspects include a pleated media made of glass fiber or synthetic materials housed in a rigid frame. Because ULPA filters generate a higher pressure drop than HEPA units, proper installation in sealed housings and, often, the use of prefilters are important to maintain airflow and extend service life.

Testing and standards typically involve challenging the filter with an aerosol such as PAO or DOP and measuring penetration at the most penetrating particle size, often referred to as MPPS. MPPS for ULPA systems generally lies around 0.1–0.2 micrometers.

Applications for ULPA filters are concentrated in environments requiring extremely clean air, such as semiconductor fabrication, pharmaceutical and medical device manufacturing, biotechnology laboratories, sterile hospital suites, and nuclear facilities. They are not designed to remove gases or odors, and their higher cost and higher pressure drop mean careful system design and maintenance are essential. Regular replacement and ensuring seal integrity are important to prevent bypass and maintain rated performance.