Traditional fiber filtration (F7, HEPA, ULPA)
In fiber filter technology, the contaminated air is lead through filter(s) for particles to stick into the filter material in the process. The quality of different fiber filters vary a lot, depending on the manufacturer. The filter’s cleaning efficiency is dependent on the filter material used, and the cleanliness level of it. Also, the efficiency of the filter varies. When the filter gets dirty, blowing power decreases, generating less airflow through the filter, resulting a pressure loss. There are various qualities of fiber filters available, e.g. coarse mesh filters for bigger particles and fine filters for smaller particles (e.g. Hepa and Ulpa). Different quality filters are often used together, such as F7 and Hepa. This requires frequent need to exchange both filters – in order to upkeep the desired level of filtering efficiency.
The fibre filter is like a net, which has been designed to catch certain sized particles, depending on the density of the net. A salmon net (F7 filter) will not catch vendaces and a vendace nets (Hepa, Ulpa) are usually not strong enough for salmon. In the same way, successful air cleaning usually requires several filter types.
Old standards for air cleaning do not serve the purpose anymore
Fiber filtration is over 50 years old technology and there are many deficiencies; the quality and amount of clean air diminishes in time, filters get clogged up, leading to increase in pressure drop, noise and energy consumption together with laborious change of filters. Therefore, in the long run, fiber filtration is often a non-economical solution. Additionally, typically used HEPA-filters in hospitals are effective only down to 0.3 µm, leaving out viruses and micro-toxins. Neither does fiber filtration remove gases and odours, for instance dangerous VOC-gases in hospitals. In worst case scenario fiber filter serves as a growth medium for microbes. Toxic microbial metabolites can get through filter and the air coming through is contaminated and the result may be fatal.
Older electric filtration
The traditional electric filtration methods, also called electronic filtration or electrostatic purification (ESP), has been developed to catch the particles using high voltage and electrical charge. Usually electric filters have been made as compact as possible, in order to ensure the theoretical and practical ability to collect particles. This kind of device may be very economical and compact, but it also results in severe problems:
- Automatic washing is not possible. Cleaning is done by dismantling the device and cleaning its interior parts in a time-consuming way.
- Electric filters usually have corona wires, which break easily and when they get dirty, the corona is not where it should be.
- The structure has been made so compact, that it gets dirty very easily, which causes leakage and a decrease of power.
Developed electric filtration technologies
New type of developed air filtration technologies that have been launched, are aimed especially for critical area air decontamination in hospitals. In the best of those the air filtration efficiency is high, collecting all particle sizes including the ultra-fine particles. The destruction of microbes is handled in an effective manner, and the system can additionally remove VOC-gases. Some of them do the air cleaning in free air flow with no pressure loss and have automatic washing for stable and constant air flow.
New type of developed air filtration technologies aimed especially for critical area air decontamination in hospitals.
Studies
A recent scientific study: EFFECT OF ELECTRONIC AIR FILTRATION TECHNOLOGY ON AIR QUALITY IN OPERATION ROOMS, realized by Faculty of Medicine, Ain Shams University, Egypt evaluated the effect of one these technologies in real surroundings. The results include that the OT airborne particle cleanliness classification level moved up from ISO 8 to ISO 6, there was highly statistical significant difference between particulate matter before and after intervention, also significant difference between active bacterial sampling and fungi sampling before and after and that the fungal colony count dropped significantly to zero and all virulent bacteria species disappeared from sample.
In Sweden at Skaraborgs Hospital, the first study of its kind is currently underway, which aims to show how modern, simple and very cost-effective technology can improve the air quality in care rooms. The goal is to halve the particle contents in the indoor air, which could contribute to reducing the number of healthcare-related infections. Health-related infections continue to be a very large medical problem and a financial challenge for the hospitals. The focus of action has long been on infection transmitted via the hands. However, most respiratory infections are transmitted via the air by so-called aerosols. According to the hospital staff performing the study there are great opportunities to reduce these significantly by electrostatic air cleaning, which is a simple and very cheap change; just "a cord on the wall". The preliminary measurement data indicate a very significant reduction in bacterial load and particle contents with electrostatic air purification. The study is intended to last for twelve months and the goal is to reduce the particle contents by at least 50 percent.
Conclusion
There is a lot of discussion today about the adequacy of traditional fiber filtration for preventing the airborne transmission of microbes, removal of the most dangerous ultra-fine particles from the air and removing the VOC-gases. The best electric air filtration methods can be a real help when addressing these issues. The issue is studied more and more, and the results are very encouraging.
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