Ultra-Low Penetration Air Filter

By Tabitha Mishra
Last updated: January 10, 2017

What Does Ultra-Low Penetration Air Filter Mean?

Ultra-low penetration air (ULPA) filters are used in commercial air filtration systems to trap airborne contaminants.

ULPA filters can capture extremely small particulates from the air, allowing them to remove all but 0.001% of particles, pollen, dust, mold, and bacteria that measure less than 120 nanometers (nm) in size. In contrast, high-efficiency particulate absorption air (HEPA) filters will only filter out particles that are 300 nm and larger.

The filter media used in ULPA filters is denser than those used in HEPA filters, reducing the airflow by 20 to 50% compared to HEPA filters.

Safeopedia Explains Ultra-Low Penetration Air Filter

Ultra-low penetration air filters are generally used in containment rooms where processes involving the use of nanoparticles are conducted. Nanoparticles cannot be handled in open-air situations and require cleanroom protocols, people wearing specialized disposable clothing or PPE, and carefully calibrated ventilation systems.

ULPA filters are used to control indoor atmospheres in the aerospace, military, pharmaceutical, and medical industries as they provide clean air that is as free of particulates as possible.

The Efficacy of ULPA Filters

ULPA filters are rated among the highest efficiency filters as it has the ability to stop the spread of airborne infectious diseases. In addition to cleanrooms, ULPA filters are also used in hospitals and healthcare organizations for their intensive care units (ICUs), operation theatres, isolation wards, and biological safety cabinets.

ULPA filters are made of spun hooked fibers rolled into paper-like material that is then formed into pleated panels to increase the surface volume of the filter. Low-porosity fibers (like cellulose acetate, carbon, ceramic, glass fiber, cotton, and polyester) are used to make these panels. The low porosity results in reduced airflow but also provides enhanced filtration.

The efficacy of ULPA filters can be further improved by using pre-filters, such as foam or electrostatic filters, to remove larger particulates so the ULPA filter can focus on finer contaminants.

Advantages of Using ULPA Filters

  • Higher efficiency than HEPA filters
  • Only one spore per million will escape the ULPA filter (compared to 10 with a HEPA filter)
  • Provides an ISO Class 3 clean room (as opposed to the ISO Class 5 work zone provided by HEPA filters)
  • Highly effective at controlling respiratory hazard and creating a safer working area
  • Greatly reduces the chance of infection in workers or contamination of products

Limitations of ULPA Filters

  • Higher cost when compared to HEPA filters
  • Restricted airflow means more ULPA filters are needed to get a number of air exchanges per hour comparable to that of a HEPA filter
  • Air passing through the filter medium undergoes a significant pressure drop, requiring a larger fan and more energy to filter the air
  • ULPA filters clog more quickly than HEPA filters and have a shorter lifespan, increasing maintenance costs

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