Ultra-low particulate air

ULPA is an acronym for "Ultra Low Particulate Air (filter)" An ULPA filter can remove from the air at least 99.999% of dust, pollen, mold, bacteria and any airborne particles with a minimum particle penetration size of 100 nanometres (0.1 µm, ultrafine particles). A ULPA filter can remove (to a large extent, not 100%) – oil smoke, tobacco smoke, rosin smoke, smog, insecticide dust.

For the model law, see Uniform Limited Partnership Act.

It can also remove carbon black to some extent.

Some Fan filter units incorporate ULPA filters.[1]

Materials used in ULPA filters

Both HEPA and ULPA filter media have similar designs.

The filter media is like an enormous web of randomly arranged fibres. When air passes through this dense web, the solid particles get attached to the fibres and thus eliminated from the air.

Porosity is one of the key considerations of these fibres. Lower porosity, while decreasing the speed of filtration, increases the quality of filtered air. This parameter is measured in pores per linear inch.

Method of functioning

Most people who are not aware of the air filtration process, believe that filtration works by physically blocking the material with a filter. Particles that are large do not get passed through and smaller ones pass.

The above process called sieving is indeed used in air filtration but it is not the only process as it is not possible to use this method to remove smaller-sized particles.

The cleaning process is based on the particle size of the pollutant. Based on these, there are four:

  • Sieving
  • Diffusion
  • Inertial impaction
  • Interception

A number of recommended practices have been written on testing these filters, including:[2]

  • IEST-RP-CC001: HEPA and ULPA Filters,
  • IEST-RP-CC007: Testing ULPA Filters,
  • IEST-RP-CC022: Testing HEPA and ULPA Filter Media, and
  • IEST-RP-CC034: HEPA and ULPA Filter Leak Tests.

See also

References
  1. http://www.escoglobal.com/products/download/FFU.pdf
  2. "IEST Recommended Practices". IEST. 2007-12-03. Retrieved 2008-01-14.
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