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). A ULPA filter can remove (to a large extent, not 100%) – oil smoke, tobacco smoke, rosin smoke, smog, insecticide dust.
It can also remove carbon black to some extent.
What is ULPA filter made of?
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 consideration of these fibres. Lower porosity, while decreases the speed of filtration, increases the quality of filtered air. This parameter is measured in pores per linear inch.
How ULPA filter cleans the air?
Most people who are not aware of the air filtration process, believe that filtration works by physically blocking the material by a filter. Particles which are large do not get pass through and smaller one 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 size 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:[1]
See also
References
- "IEST Recommended Practices". IEST. 2007-12-03. Retrieved 2008-01-14.