HEPA Filtering
HEPA (High Efficiency Particulate Arrestance or Air) and ULPA filters have been in use around the world for many years. Commencing in the late 1940s, the first HEPA filter was developed mainly for military gas mask filters and for protection against radionuclides in the nuclear industry.
HEPA filters are critical in the prevention of the spread of airborne bacterial and viral organisms and, therefore, infection. Medical-use HEPA filtration systems also incorporate high-energy ultra-violet light units to kill off live bacteria and viruses trapped by the filter.
Designed to capture airborne particles, the HEPA filter doesn't capture everything. A small number of particles larger than 0.3 microns and smaller particles pass through. This includes small bacteria (some as small as 0.1 micron), viruses measuring between 0.005 and 0.2 microns, some smoke particles, and gases.
Typical Applications
The human body has difficulty with 0.3 micron particles, this size can float in the air, and poses risk to asthma and allergy sufferers. A HEPA filter traps the fine particles (such as pollen and dust mite faeces) which trigger symptoms. To overcome this issue, some of the best-rated HEPA units have an efficiency rating of 99.995%, and are used in biomedical environments to prevent the spread of airborne bacterial and viral organisms. Along with their use in aircraft, HEPA filters are now appearing in motor vehicles. Tesla is the first manufacturer to claim the use of a HEPA filter, “allowing medical-grade air to fill the cabin, no matter what is going on outside,” (www.Tesla.com).
Construction of the filter
Fibre diameter, filter thickness, and face velocity are critical factors affecting the efficiency of a filter. HEPA filters are composed of a mat of randomly arranged fibres, typically fiberglass, and with diameters between 0.5 and 2.0 microns, and some have cellulose and a synthetic blend. For maximum efficiency, it is important that air does not bypass the filter. All seals must be fastened tightly, letting nothing flow past the filter.
Applying HEPA standards to vacuum cleaners
Good quality vacuum cleaners use HEPA filters as part of their filtration system.
According to Safework Australia, all asbestos vacuum cleaners must have a HEPA filtering system that is capable of trapping and retaining 99.97% of all mono-dispersed particles of 0.3 microns in diameter. Although, this is perhaps true of a brand new box vacuum cleaner, very quickly the “asbestos vacuum cleaner carries the dents and knocks associated with a hard working life,” Safework Australia (www.safeworkaustralia.gov.au)
The fact that the vacuum cleaner is fitted with a HEPA filter is not a good indication that will comply with the 99.97% filtration performance rate under field conditions. Each time the HEPA filter is replaced, and when the vacuum cleaner is taken apart for decontamination purposes, or it undergoes electrical or mechanical maintenance/repair, the integrity of the HEPA filter is compromised. “Full bags are regularly removed and replaced, but it has been observed that the HEPA filter is only occasionally replaced,” Safework Australia.
To ensure optimum efficiency, a HEPA filter in a vacuum cleaner must be designed so that all air drawn into the machine is expelled through the filter, without leakage. This is often referred to as "Sealed HEPA."
Vacuum cleaner filters marketed as "HEPA-like" will typically use a filter of a similar construction to HEPA, but without the filtering efficiency. Because of the extra density of a HEPA filter, HEPA vacuum cleaners require more powerful motors to provide adequate cleaning power.
Nilfisk vacuum cleaners equipped with HEPA filters are designed to be used in hospitals, hotels, accommodation facilities, office and retail environments and industrial sites. Nilfisk also manufactures specialist asbestos certified vacuums, as well as vacuums for use in manufacturing hazardous or explosive environments.
Standards
At Nilfisk, our efficiency of filtration standards complies with the EN1822 standard. This definition includes:
EPA10 – EPA 12 Efficiency Particulate Air Filer
EPA 13 – HEPA 14 High Efficiency Particulate Air Filter
ULPA 15 – ULPA 17 Ultra Low Penetration Air Filters
HEPA class | retention (total) | retention (local) |
E10 | > 85% | --- |
E11 | > 95% | --- |
E12 | > 99.5% | --- |
H13 | > 99.95% | > 99.75% |
H14 | > 99.995% | > 99.975% |
U15 | > 99.9995% | > 99.9975% |
U16 | > 99.99995% | > 99.99975% |
U17 | > 99.999995% | > 99.9999% |
Nilfisk has been developing cleaning machines for more than 110 years and is one of the world’s leading manufacturers of professional cleaning equipment.
Disclaimer
This information should be used as a guide only. For detailed information, contact Safe Work Australia for compliance, WHS and application specific guidelines. Contact SAI Global for HEPA specifications.
