Air Filtration for Buildings Air Purifier against Covid

Make short work of Covid-19!


Whether in a classroom, classroom or seminar room, doctor's practice, office or restaurant - the antiviral air purifier ensures clean healthy indoor air everywhere. The latest development from the expert in filter systems, Hengst SE, has been tested by scientists at the Westphalian Wilhelms University in Münster and is already in use in hundreds of schools, daycare centers, medical practices, offices and restaurants.

After only 10 minutes, the virus load of the room air drops by 50%, after only 30 minutes even by 90% (room size 80 m²) at an air exchange rate of 6 times per hour.

The HEPA class H14 combination filter achieves a filter efficiency of ≥ 99.995 %. Fine dust, aller - gene, bacteria as well as smallest viral contaminated aerosol droplets are reliably filtered out of the room air. And this without the use of UV-C irradiation.

The noise level in continuous operation at 800 m³/h nominal volume flow is below 35 db(A). The Power Diffusor Pro distributes the intake air evenly towards the room ceiling without any disturbing draught effects. This ensures the best possible air circulation throughout the entire interior. + The robust, flow-optimized design and energy-efficient technology guarantee safe continuous operation and low energy consumption.

The air purifier is controlled via a clear display. Here, the room size can be conveniently entered, which automatically sets the optimal performance of the purifier, the air exchange rate can also be adjusted at any time (a 4-fold exchange rate per hour is recommended). A weekly schedule can be programmed in the menu, as well as a silent or booster function and an overrun time can be activated. The filter saturation as well as the room air quality are displayed and the device can be controlled via a weekly schedule. The air purifier also has a daylight sensor and a timer.

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Advantages Air Purifier against Covid – Your customer benefit at a glance:

  • The HEPA class H14 combination filter effectively removes ≥ 99.995% of airborne viruses and aerosols.

  • Fine dust, allergens, bacteria as well as the smallest viral contaminated aerosol droplets are reliably filtered out of the room air.

  • Without the use of UV-C irradiation.

  • Reduction of virus load by >90 % after 30 minutes (room size 80 m²). At an air exchange rate of 6 times per hour.

  • The noise level in continuous operation at 800 m³/h nominal volume flow is <35 db(A) (as of October 2022).

  • The Power Diffuser Pro distributes the intake air evenly towards the room ceiling without any disturbing drafts. This ensures the best possible air circulation throughout the entire interior.

  • The robust, flow-optimized design and energy-efficient technology guarantee safe continuous operation and low energy consumption.

  • Made in Germany.


Here you will find (almost) all the answers to your questions at a glance:

What are aerosols?

Aerosols are generally defined as a fine distribution of tiny suspended particles in a gas, in our case the air. The current discussion focuses primarily on droplets of different sizes and quantities that people exhale with the air when they breathe and speak. Larger droplets (> 5 µm) sink down quickly due to gravity, while small and very small droplets can float in the air for a long time. The mixture of these very small droplets (especially suspended particles < 1 µm) and the surrounding air is called an aerosol; the smallest droplets themselves are often called aerosol particles - also to distinguish them from larger droplets. In infected persons, these exhaled droplets and aerosol particles contain infectious viruses, which are distributed in the surrounding air via the aerosol. Indirect infection by aerosol transmission is considered an important route of transmission, particularly in enclosed spaces [i, ii].

Will airing become superfluous with the air purifier?

The is a recirculating air purifier and was specially developed for the safe separation of airborne viruses, germs, bacteria and spores to clean the room air of harmful aerosols in the shortest possible time. This is done to reduce the risk of infection. The device does not bring fresh air into the room from outside. However, it is well known that people need oxygen to breathe, and it is also important that the CO2 exhaled by people does not concentrate too high in the room. By the way, these relationships apply completely independently of the current corona pandemic. Therefore, rooms must be ventilated regularly, as usual, to maintain good breathing air quality and to supply fresh air to the room.

How effective is the antiviral air purifier?

Our simulations show that the, if positioned and adjusted correctly, can halve the virus load in a room already within approx. 10 min. After 30 min, a reduction in the concentration of viruses of up to 90% can be achieved. This effectiveness significantly reduces the risk of indirect infection. To ensure the effectiveness of the, it is important that the set volume flow of the device is adjusted to the room size (see also "How high must the air exchange rate of the air purifier be?").

Can an indirect infection be prevented with the

The risk of infection due to infectious aerosols in enclosed spaces is determined on the one hand by the virus load (i.e., virus concentration) in the room and on the other hand by the exposure time, i.e., the duration of stay of an uninfected person in this room. With increasing virus concentration and with increasing exposure time, the risk of indirect infection also increases. How exactly to quantify the risk and where exactly the boundary to an infection is located, very extensive studies are still ongoing, e.g. [iii, iv]. However, it is not possible to simply reduce the time people spend indoors, e.g., in schools, as long as one wants to maintain face-to-face teaching. Therefore, indoor air purifiers aim to reduce the other crucial factor, the virus concentration in the room. See also [8], which can be used to estimate the risk of infection depending on room size, room occupancy and use, and ventilation situation. The is able to very effectively lower the concentration of (infectious) aerosol particles indoors. It thus significantly reduces the risk of indirect infection by the SARS-CoV-2 virus and other viruses.

Can use of the device release me from regulatory requirements?

No, the currently applicable regulatory requirements regarding distance, mouth-nose protection, etc. are not overridden by the use of the device. The combination of the AHA rules with ventilation and recirculating air filtration represents the best possible protection against infection.

How high must the air exchange rate of an air purifier be?

Various publications point out that the effectiveness of indoor air purification devices depends in particular on achieving a sufficiently high air exchange rate. The air exchange rate is the ratio of the volumetric flow rate of the device and the room volume (i.e. floor area x height of the room). Studies citing this relationship include [3, 4]. It is shown here that an increase of the volume flow in relation to the room volume improves the cleaning performance accordingly - and vice versa. On the other hand, an ever-increasing recirculated air volume flow in rooms has a negative effect on people's well-being. In [7], an air exchange rate of 6 is suggested as a reasonable setting to ensure adequate purification of indoor air. For a room with a floor area of 8m x 8m and a room height of 3m (i.e. a room volume of 192 m³), for example, this results in an air exchange rate of six at a volume flow rate of 1,152 m³/h.

What kind of filter element is used?

A HEPA combination filter of filter class H14 according to the EN 1822 or ISO 29463 standard is used, consisting of a specially matched pre-filter and main filter. Pre-filter and main filter are offered as an integrated HEPA H14 filter set for easy handling.

Why is a HEPA filter of filter class H14 used?

Many sources recommend that mobile room air cleaners should be equipped with high-separation filters of filter classes H13 or H14, as only these are effective in reducing viruses in the air. One such source is the German Federal Environmental Agency [v]. In the study of the Bundeswehr University in Munich [7] the effectiveness of air cleaners for the filtration of infectious aerosols in the ambient air was investigated and there the use of H14 filters is explicitly recommended.

What is a HEPA filter?

Air filters can be divided in terms of their efficiency into coarse dust filters, fine dust filters and HEPA filters. The HEPA filters are those with the highest efficiency. HEPA filters are standardized in the EN 1822 and ISO 29463 standards. HEPA filters belong to the HEPA filters and are used in places where very high cleaning performance is required, for example in hospital operating rooms. "HEPA" also stands for "High efficiency particulate air filter".

What exactly does H14 mean and does the HEPA H14 filter really only filter particles from 0.1-0.3 µm?

A HEPA filter has very high collection efficiencies for virtually all relevant particle sizes due to the effective collection mechanisms. This also makes sense, because impurities in the (breathing) air can have very different particle sizes. For example, viruses or smoke particles are significantly smaller than bacteria, and these in turn are significantly smaller than pollen or dust particles. A HEPA filter is tested at different particle sizes. In order for a HEPA filter to be labeled with a certain filter class, it must achieve certain minimum collection levels for the particle size that it separates most weakly (the so-called MPPS "most penetration particle size"). This means that it must achieve even higher collection efficiencies than at the MPPS for all other relevant particle sizes. This also applies to particles even smaller than 0.1 µm. The MPPS is usually in the range between 0.1 and 0.3 µm. A Class H13 filter must achieve at least 99.95% collection efficiency at the MPPS. A Class H14 filter must even achieve at least 99.995% here. As mentioned, for all other relevant particle sizes, the efficiency is then even higher. In addition, the standard stipulates that each individual filter element must be tested at the factory to ensure that it is leak-free; this means that there is a 100% check on the efficiency of the filter elements. It can therefore be assumed that filter elements that have been qualified as H13 or H14 in accordance with the above-mentioned standards will actually separate almost ALL particles. The filter set in the achieves filter class H14 at nominal volume flow and smaller air volumes.

Why does the not use UV-C radiation or heat in the device to destroy viruses?

The use of UV-C rays in non-industrial applications has been little tested. Depending on the technology, it cannot be ruled out that waste products (endotoxins) are produced which may be harmful to humans. The German Federal Environment Agency is therefore critical of the use of this technology [8]. Thanks to the HEPA H 14 filter, viruses and bacteria are safely trapped inside the air purifier. We do not consider additional heating to be necessary, since viruses cannot multiply in the filter element and become inactive ("die off") on porous surfaces after a relatively short time anyway. We therefore refrain from unnecessary processes to destroy viruses in the filter, as such processes only consume additional energy without providing further protection.

How often must the filter element be changed?

The filters must be changed every 6 months if used as intended and for an average of no more than 40-50 hours per week. Replacement filters are available at Depending on the room conditions and types of use, a shorter or longer service life may also be indicated. However, according to VDI 6022, filters must be changed after 12 months at the latest.

How do I change the filter?

The can be opened with an enclosure key supplied. The HEPA combifilter itself is clamped in the housing via two nuts and can be loosened with a standard wrench (SW17). In addition, the filter change is shown in the operating instructions in an easy-to-understand and pictorial manner.

What do I have to pay attention to when changing the filter and how must the installed filter be disposed of?

When changing filters, care must be taken not to accidentally release dust particles that come into contact with mucous membranes or are inhaled. After all, an incalculable number of types of contamination have accumulated in the filter during operation. Therefore, it is a precautionary measure to please wear appropriate protective equipment for the change according to the operating instructions. The used filter must be disposed of in a tear-proof, sealed plastic bag of suitable size. The original spare part is packed in a bag suitable for disposal. The materials used for the filter can usually be disposed of in household waste, but if in doubt, please inform yourself about deviating local regulations.

How much space does the need and where do I have to place the device?

The dimensions of the L are: Length 560 x width 730 x height 1.68 mm. In principle, the device can be placed anywhere in the room, both in the center of the room and further to the edge. The air inlet and outlet should not be directly obstructed or covered and should have a distance of at least 30 cm from the walls. Separate considerations may be necessary for special room geometries such as long hallways, or angled floor plans. The same applies to room dividers or particularly large furniture that protrudes into the room: In these cases, special care must be taken to find an installation location for the unit that allows an even flow through the room. In the case of very large rooms or very unfavorable floor plans, however, several room air cleaners should possibly be used. If there is a joist in the room, it may make sense to place the device directly underneath it, see => "I have several in use, how do I best distribute them in the room?".

How is uniform clean air distribution ensured?

The special design of the PowerDiffusor Pro with its specially developed design ensures a uniform, room-filling ventilation with filtered air. In order to achieve sufficient cleaning performance, the correct air exchange rate is of particular importance, see => "How high must the air exchange rate of the air purifier be?". The placement must be carefully planned, see => "How much space does the need and where do I have to place the device?". Will the work even if there are large pieces of furniture in my room or other obstacles could deflect the airflow? We designed and developed the for crowded classrooms, offices or restaurants. The simulations clearly show that the function is not restricted by tables, chairs or even people, for example. This is also shown in practical measurements, which have been carried out, for example, by the University of the German Armed Forces [7]. As long as no objects or objects directly cover the, the function is not restricted. The placement should be chosen carefully (see also "How much space does the need and where should I place the device?").

I have several in use, what is the best way to distribute them in the room?

This will mainly be the case if you want to equip either a very large room or a room with an angled geometry, such as an L-shaped floor plan. The devices should then be placed a few meters apart from each other in the room. And in such a way that each of them is "responsible" for cleaning a part of the room. The best way to find the placement is to imagine dividing the room into two halves with a partition wall and then placing the device appropriately in the respective part-room.

Can I change locations quickly with the

Thanks to sturdy wheels and the device height of 1.95m, which allows it to pass through all normal doors and elevators, the robustly designed room air purifier can quickly change the place of use.

What do I have to consider during commissioning?

The antiviral air purifier is delivered already assembled and equipped with a HEPA H14 filter set, and commissioning requires only a few simple steps. The cold appliance plug must be plugged into the device and a standard 230 V socket. Please switch on the device at the on/off switch. The room size can be entered via the easy-to-use display and the unit automatically sets the correct volume flow. Please also refer to the operating instructions here.

Is overnight operation necessary?

No, it is quite sufficient to start the when the room is in use. The L air purifier has a booster function that automatically switches on a fixed maximum power. Likewise, a daylight sensor can be switched on, with which the device automatically turns off in the dark.

Product variants (Variante L) (Variante L)

1,68 x 0,73 x 0,56 m
135 kg
Sound pressure level at 1 m distance at 800 m3/h <35 db(A), sound pressure level at 1 m distance at maximum volume flow at 2000 m3/h 46.2 db(A)
Max. Air output
1.800 m³/h
Air exchange rate
Variable adjustable via the touch display. Recommendation according to VDI-EE 4300 sheet 14, the device should be set to a 4-fold air exchange per hour.
230 Volt / 50Hz
Power consumption
250 watts at nominal volume
Filter Efficiency
≥ 99.995 % of all particles incl. bacteria and viruses
Filter combination
HEPA H14 combination filter according to standard EN 1822 or ISO 29463


Was sind die Vorteile eines großen Luftreinigers gegenüber eines kleinen Luftreinigers?

  • Konstruktionsbedingt ist bei kleineren Geräten die Luftwechselrate deutlich geringer als die empfohlenen 6 x pro Stunde, daher eignen sie sich nur für sehr kleine Räume. Siehe => „Wie hoch muss die Luftwechselrate des Luftreinigers sein?“.
  • Ein kleineres Gerät stößt die gereinigte Luft auf Körper- oder Kopfhöhe oder gar bodennah aus, die entstehende Zugluft wird als unangenehm empfunden (direktes Anströmen, Zugluft).
  • Nur in einem großen Gerät haben die wichtigen HEPA-Filter eine ausreichende Filterfläche, um einen langfristigen Schutz ohne ständigen Filterwechsel zu gewährleisten.
  • Um eine geringe Lautstärke sicherzustellen, muss eine ausreichende Schalldämmung verbaut sein, die nur in größeren Geräten Platz findet.
  • Aus dem gleichen Grund setzt man in einem großen Gerät einen entsprechend leistungsfähigen Ventilator ein, den man in dem angegebenen Nennbereich des Volumenstroms nicht voll auslasten muss. (Variante M) (Variante M)

1.08 x 0.45 x 0.40 m (with handles and door)
50 kg
42 dB(A) - Sound pressure level at 1m distance at nominal volume flow rate
Max. Air output
770 m³/h
Air exchange rate
6 x per hour for a room up to 50 m²
230 Volt / 50Hz
Power consumption
75 Watt
Filter Efficiency
≥ 99.995 % of all particles incl. bacteria and viruses
Filter combination
HEPA H14 main filter and F7 activated carbon pre-filter according to standard EN 1822 or ISO 29463

Test passed! Room air in. Clean air out.

The features a HEPA filter class H14 and is equipped with a nominal volume flow of 1,150 m³/h. This means that particle reductions of between 94 and 95 % were achieved under reproducible conditions in a practical test by an independent accredited test laboratory. This was achieved with the relevant particle size of 0.5 µm. The [to the test report] thus proves that it is an effective aid in reducing the risk of corona infection.

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