Viruses are organic structures that spread as virus particles, known as ‘virions’, and usually have a diameter of 0.015 µm to 0.4 µm (µm = micrometer). One micrometer corresponds to a thousandth of a millimeter. Viruses are therefore very small and allocated to the PM1 category. The classification of particles into the categories PM10, PM2.5 and PM1 is based on the "National Air Quality Standard for Particulate Matter" of the US Environmental Protection Agency (EPA) and is accepted and used worldwide. This classification plays a particularly important role in air filtration, as the size of the particles to be filtered is important in mechanical filtration. The choice of right filter is decisive here.
They do not themselves consist of cells and can only reproduce with the help of other cells. For this reason, they are fundamentally dependent on living organisms as hosts. Like bacteria, parasites and fungi, viruses belong to the category of pathogens and cause health-damaging conditions in their hosts.
Pathogens compared: viruses, bacteria and parasites
In contrast to viruses, bacteria are unicellular organisms and can multiply via cell division. Parasites also consist of cells. However, like viruses, they exploit the metabolic processes of a host to reproduce themselves.
Transmission path: Droplet and contact infection
The Covid-19 (Corona) virus can cause diseases ranging from a normal cold to severe disease progression. The WHO has declared the outbreak of this virus to be a health emergency of international concern.
Transmission path: droplet and contact infection
“Standard” flu is one of the most common viral infections. The World Health Organization (WHO) estimates that between 10-20% of the world's population is affected every year.
Transmission path: Droplet infection
Measles is regarded as a typical childhood disease. Transmission is prevented by vaccines. Cases of infection are still widespread in Africa.
Transmission path: Smear infection
Ebola can be transmitted by animals and between people. It causes the deadly Ebola fever.
Transmission path: Droplet and contact infection
The H1N1 virus can infect both humans and mammals. In 2009, over 500,000 people in 200 countries were infected within a matter of months.
Not all viruses are equally contagious. While some pathogens are only transmitted through intensive contact, others can be spread simply by physical proximity. In the case of infection paths that use air as the transmission medium, effective air filter concepts can be used to combat these pathogens. The quality of the room air and thus the air filtration have no influence on other sources of infection, such as contaminated food or water.
Viruses that colonize the respiratory tract and mucous membranes are mainly absorbed through the ambient air. When we sneeze, cough or speak, tiny droplets containing virus particles are released into the air. The tiniest droplets are suspended in the air for a long time and are inhaled by other people. Droplets >5µm sink relatively quickly and reach objects and surfaces from where they are then indirectly spread.
With contact and smear infections, the pathogens are transmitted by touch. Sick patients may also have viruses on the palms of their hands. If they shake hands with other people, the viruses are transmitted. Infection can also be indirectly transferred via objects such as door handles. Thorough hand washing is an effective way of preventing contact infections.
In recent weeks, this topic has attracted a great deal of media attention. So do respiratory masks offer sufficient protection against viruses or not?
Wearing a normal respiratory mask or a respiratory mask of class FFP1 is not sufficient protection against viruses. It is only suitable to avoid contaminating others by droplet infection if you are already ill yourself. Class FFP2 and FFP3 respiratory masks are recommended for hospital staff, care workers and other groups of people with an increased risk of infection. In the case of direct contact with infected individuals, FFP3 respiratory masks offer the best protection against pathogens such as viruses and bacteria.
In addition, disposable products (including most respiratory masks) should be changed several times a day. They gradually become damp from breathing and lose their protective effect once saturated.
We produce filter media suitable for the assembly of respiratory masks in protection classes FFP2 and FFP3.
|FFP1||FFP1 respiratory masks should only be worn where only non-toxic dusts and respiratory irritants are expected. They are used up to 4 times the occupational exposure limit value and filter at least 80% of airborne particles >0.6 μm.|
|FFP2||FFP2 respiratory masks provide protection against solid and liquid aerosols and airborne infectious agents that are hazardous to health. They are used up to a 10-fold excess of the occupational exposure limit value and filter up to 94% of particles >0.6 μm from the air breathed. According to the common opinion of experts the minimum protection class against virus infections.|
|FFP3||FFP3 respiratory masks offer the highest possible protection against toxic and harmful aerosols and airborne infectious agents within the protection classes for masks of EN149. They are used up to a 30-fold excess of the workplace limit value and filter at least 99.5% of particles >0.6 µm from the air we breathe.|
In buildings, offices and public facilities, high-performance air filtration reduces the risk of pathogens such as viruses and bacteria. It therefore makes sense to use individually adapted air filtration systems for the following sensitive areas:
e.g. in isolation rooms, operating rooms, treatment rooms, corridors
e.g. schools, universities, sports halls, department stores, concert halls, etc.
e.g. in buses, trains, ships and aircrafts (cargo hold and cabin ventilation)
e.g. in cars
A common infection pathway is droplet infection. The virions are distributed in the air by droplets of <5 µm. Powerful filter elements and multi-stage air filtration systems can almost completely separate these particle sizes and thus effectively reduce the pathogen concentration in the room air:
Air filters of different filter classes are combined in a multi-stage system to ensure the desired indoor air quality. The basis for perfectly matched filter stages and the classification of air filters is the ISO 16890 test standard. Air filters are classified into the corresponding ISO classes based on their separation efficiency of the different particle sizes PM10, PM2.5 and PM1. For HEPA filters (EPA, HEPA and ULPA filter classes), the new ISO 29463 provides orientation based on the European filter standard EN 1822.
Filter stage 1Pocket filters initially separate most of the larger particles (PM10) such as dust and pollen from the supply and recirculated air. Their low pressure drops make them particularly energy efficient.
Filter stage 2Almost all PM2,5 particles are filtered in filter stage 2. Cassette filters excel here with their high dust holding capacity and stable separation efficiency.
Filter stage 3The third stage with HEPA filters is responsible for ensuring sterility and clean room air. A HEPA/ULPA filter of filter class H14 removes more than 99.995 % of the remaining particles, germs and viruses from the air – and thus effectively minimizes the risk of contracting infections indoors.
Here is an exemplary representation:
Individually tailored concepts
Every room has its own specific requirements. The most effective air filter system is therefore always a solution that has been individually tailored to meet the local conditions and individual needs.
Minimize the risk of contamination through individual services and solutions
- Comprehensive, individual planning and conception of your air filtration system
- Commissioning and implementation by our expert technicians
- Maximum hygiene protection through compliance with VDI Guideline 6022
- Regular inspection and maintenance with Viledon filterCair
- Professional replacement of contaminated filter elements
How do air filters work to protect against viruses?
A common infection pathway is droplet infection. The virions are distributed in the air by tiny droplets of <5 µm. Powerful filter elements can separate these particle sizes almost completely from the air and thus reduce the pathogen concentration in the room air.
The recirculation component of the ventilation system plays a major role in the germ load of rooms. High levels of fresh air reduce the virus concentration in contaminated rooms because the contaminated air does not circulate within the building. The risk of becoming contaminated by germs in the circulating air is negligible.
What happens to viruses in air filters?
Powerful HEPA filters separate the tiniest particles such as viruses to a particularly high degree. Because they cannot reproduce themselves, once separated the viruses remain in the filter and decompose over time. Microbiologically inactive filters such as our HEPA filter H14 (according to EN 1822) capture more than 99.995 % of all particles and aerosols to which viruses can adhere.
Since viruses need liquid water to survive, they decompose relatively quickly in the filter elements, as long as these are not saturated. This is true even at higher levels of relative humidity.
Can a filter itself become a source of contamination?
To prevent air filters from becoming a source of germs themselves and dispersing them around buildings, proper operation and maintenance are crucial. Systems that meet the requirements of VDI Guideline 6022 are designed to offer comprehensive protection from a hygienic point of view – from planning and operation to maintenance.
Together with the professional replacement of filter elements, expert servicing of the entire ventilation and air-conditioning system (including the thermodynamic treatment steps of heating, cooling, humidifying and dehumidifying) minimizes the risk of filters becoming a source of contamination.
How are contaminated filters replaced?
Filter elements that have come into contact with highly infectious viruses, such as the novel corona virus, must be replaced by experts following a specific procedure. The act of changing the filters has the effect of contaminating the rooms. This means that they must be sterilized or decontaminated before being used again. This can be done by spraying with hydrogen peroxide, via heat or radiation sterilization, or through ethylene oxide sterilization.
Because of this, many filter systems that are used in particularly sensitive areas such as isolation stations have special protocols to ensure contamination-free filter changes.
Do the maintenance intervals have to be increased due to viruses in the air?
If a ventilation system is properly operated and maintained according to schedule, no additional filter changes are necessary. Air filters are not usually a source of contamination when maintained properly. However, we do recommend air filters for ventilation systems with circulating air operation, change the filters at the latest after the pandemic has subsided.
It is also not necessary to increase the cleaning cycles of ventilation ducts, as a ventilation system is not a source of contamination if the recommendations of VDI 6022 for air conditioning systems are observed. Viruses that adhere to small droplets or particles can of the air flow is difficult to deposit in the ventilation ducts. They are normally carried on by the airflow. It is much more important to increase the fresh air proportion and minimize, if possible eliminate the recirculated air proportion.
Operators of ventilation systems are often faced with special challenges regarding the correct handling of viruses. For this reason, many institutes and organizations are dealing with this critical topic, especially due to the current situation. For further information we have therefore compiled a list of links to interesting and informative websites, which we constantly update and expand for you:
ASHRAEAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers
Current information on the use of COVID-19:
Document on airborne infectious diseases:
(as of 05 February 2020)
EUROVENTEurope's Industry Association for Indoor Climate (HVAC), Process Cooling, and Food Cold Chain Technologies
REHVAFederation of European Heating, Ventilation and Air Conditioning Associations
Current information on the use of COVID-19:
Guidelines for handling COVID-19:
(as of 17 March 2020)
Robert Koch Institute (RKI)Central institution of the German Federal Government in the field of disease surveillance and prevention
Current information on COVID-19:
World Health Organization (WHO)United Nations Coordinating Authority for International Public Health
Current information on COVID-19:
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Robust in sustained use, high operational dependability and reliability even in the face of extreme moisture and wet conditions. They enable the energy-efficient operation of air conditioning systems. This translates to energy cost savings and a reduction in CO2 emissions.Show details in e-catalog
The premium class in patented quality. Highly stable filter designs for the greatest possible operational dependability even under extreme loads. Water-repellent. Long service life, making them very economical.Show details in e-catalog
Satisfy the highest requirements for clean air and sterility of filter classes E11 to U15. Reliable protection against particles and microorganisms. The MiniPleat technology ensures a homogeneous media velocity for safe, economical operation.Show details in e-catalog