4 FILTRATION STAGES FOR OPERATOR’S SAFETY
The RGS vacuum cleaners are equipped with four-cascade filter systems, which help to keep low bacterial loads in the workplace
HEPA AND ULPA FILTERS
These filters are part of the so-called category of “Absolute Filters”
The terms HEPA and ULPA derive respectively from the English acronyms “High Efficiency Particulate Air filter” and “Ultra Low Penetration Air”.
Filtration mechanism
- The interception occurs when a contaminating particle passes within the distance equal to the radius of a particle of a filter fiber, touching the fiber, it is removed from the airflow. Particles Exceeding a particle radius will not be trapped by a fiber.
- Inertia occurs when a particle of large size, unable to adapt to the change in the direction of the air near a filter fiber, remains trapped on the fiber. The inertia of the particle ensures that it continues along its original trajectory instead of circumventing the fiber and will consequently be captured
- The diffusion is based on the Brownian motion of the gas particles. Small particles (typically 0.1 μm or less) tend to travel irregularly, creating random movements while interacting with gas molecules. This irregular movement causes the contaminating particles to get stuck in the filter fibers.
HEPA AND ULPA FILTERS
By understanding these three methods, it becomes clear why particles around 0.3μm are more difficult to be filtered. Particles less than 0.1μm are easily trapped by diffusion, while particles larger than 0.4μm are trapped by inertial impact. Particles between 0.1 and 0.4μm are therefore too large for effective diffusion and too small for inertial impact and efficient interception, so that the filter efficiency decreases within this range.
By specifying the efficiency of a HEPA filter of 0.3μm, a variant of the minimum filter efficiency is described.
HEPA AND ULPA FILTERS
Filtering efficiency
The evaluation of the filter medium has index of lower efficiency or maximum penetration for a specific particle size. The certification of the class is based on the tests required by EN1822 and are indicated in the following tables:
EPA – HEPA FILTER
| Class | Efficiency | Penetration |
|---|---|---|
| E10 | > 85% | — |
| E11 | > 95% | — |
| E12 | > 99.5% | — |
| H13 | > 99.95% | ≤ 0.05 |
| H14 | > 99.995% | ≤ 0.005 |
UPA-FILTER
| Class | Efficiency | Penetration |
|---|---|---|
| U15 | > 99.9995% | ≤ 0.0005 |
| U16 | > 99.99995% | ≤ 0.00005 |
| U17 | > 99.999995% | ≤ 0.000005 |
ULPA filters are closely related to HEPA filters but they are even more efficient. ULPA filters are specific for removing 99.999% of contaminants of 0.12μm or more in diameter.
The following chart shows the overlap in the capacities of the ULPA and HEPA filters.
HEPA AND ULPA FILTERS
Conclusions
The 0.3 μm standard was chosen to test the HEPA and ULPA filters because this particle size is actually the most difficult to be filtered.
Particles measuring 0.3 μm are small enough to fit with many filter fibers and are also heavy enough to have sufficiently inertia to fly generally in straight lines. A straight flight path makes a particle more likely to pass through a filter without touching a fiber. The smaller particles have less inertia and are therefore more at the mercy of microcurrents and other random forces. This causes their flight patterns to wind and resemble that of a confused hummingbird. With these random and tortuous flight paths it is much more likely that they will encounter a fiber when passing through a filter. Once they meet a filter fiber that lack inertia makes them even more susceptible to being trapped by forces such as static electricity. This phenomenon is supported by a NASA study that found HEPA and ULPA filters very efficient in capturing particles in the size range of 0.1 μm.
4 FILTRATION STAGES FOR OPERATOR’S SAFETY
Does the adoption of HEPA and ULPA filters on vacuum cleaners reduce the spread of the COVID-19 virus?
Assuming that the COVID-19 virus is approximately 0.1μm in size, HEPA filters have demonstrated to be able to capture more than 99.9% of the viral particles that reach them and ULPA filters up to 99.999%.
We could say that these filters are effective in capturing airborne viruses and that they are attracted inside the vacuum cleaner. In this case, without the adoption of adequate filters, they would return to the environment through the exhaust air of the aspirator itself. Therefore, the adoption of a HEPA or ULPA filter will surely have a retention effect of almost all particles and microorganisms up to 0.1μm that are sucked in.
It should be specified that only a part of the viruses present in the environment will be intercepted by the air flow of the vacuum cleaner and therefore the use of the vacuum cleaner fitted with HEPA and ULPA filters, will produce a benefit for the operators but cannot be considered as a sanitizing system or total protection of the environment in which it is used.
It is necessary to follow the rules established by the relevant bodies by adopting the appropriate individual protection devices accordingly.
HEPA AND ULPA FILTERS
Use of UV-systems (ultraviolet rays) to produce advanced oxidation processes (AOP- Advanced Oxidation Processes)
The UV cells inside the HEPA and ULPA absolute filters of the vacuum cleaners, in addition to eliminating part of the microorganisms trapped in the same filters, and therefore keeping them cleaner, produce a series of oxidants (peroxides, hydroperoxides, ozonide ions, superoxide, hydroxide ions) which are released into the environment through the air coming out of the vacuum cleaners themselves.
These so-called “friendly” oxidizers and therefore not harmful to humans contribute in part to the reduction of bacteria, viruses and other pollutants present in the air surrounding the vacuum cleaner during the use of it.
The oxidants produced return to the state of oxygen and hydrogen after oxidation of the pollutant.
The oxidants produced return to the state of oxygen and hydrogen after the oxidation of the pollutant.
Are oxidants produced by UV-AOP systems effective against COVID-19 virus?
There are currently no specific tests on Coronavirus (COVID-19) as there are a limited number of facilities capable of testing this virus and at the present time priority is given to tests that have a direct relationship with recent outbreaks.
Test results showing a 99 % reduction in viruses similar to Covid 19 have been validated and therefore it could be assumed that these systems are also effective against the current coronavirus, but till now we cannot have reliable data supported by scientific analysis made by competent bodies.
