Dry air

Woman in the water

The skin – the largest human organ is in constant interaction with its environment. The humidity in the air has a direct effect on our skin. Indoor air that is too dry dries out the skin and leads to itching and early skin aging. Creams are one way to lessen the effects – but they don’t remove the cause! 

Dry heating air: The main problem for dry mucous membranes, reddened and strained eyes, itching – and a weakened immune system. Moisture is measurably withdrawn from the skin .


  1. Dry air and health
    1. Moisture influences cell regeneration and the aging process of the skin
    2. Air hygiene: essential for our health
  2. Not all air is the same: open air vs. indoor air
  3. Optimal air hygiene in offices and interiors
    1. Relative humidity and temperature
    2. Air climate and humidity – focus on health and wellbeing
    3. CO2 pollution and significance for air quality
    4. Professional air humidification as a multi-perspective approach to health protection
  4. Overview of the humidification processes
    1. Passive humidification processes
    2. Aerosol humidifiers
    3. Direct evaporator – the natural humidification
    4. We recommend: direct evaporation with active water disinfection
  5. FAQ: Avoid dry air
    1. What does “ventilate properly” mean?
    2. How do I heat correctly?
    3. How do I ensure the correct humidity?
    4. How can the humidity be increased / influenced?
    5. How can the humidity be increased / influenced?
    6. What do “absolute humidity” and “relative humidity” mean?

Moisture influences cell regeneration and the aging process of the skin

Our body consists of around 13 billion cells. Each of these cells consists of a large percentage of water and is therefore dependent on a supply of water for comprehensive cell health. Whether and how well a cell can regenerate also depends on whether there is sufficient fluid available inside the cell.

For the skin in particular, it becomes clear that air humidity plays an essential role in health, not least because the largest human organ with its entire surface of almost 20,000 cubic centimeters is exposed to the ambient air 24 hours a day, 365 days a year. 

Not only can connections be made between humidity and skin health . The relationship between humidity, well-being and general health and susceptibility to infection is fundamentally more complex.

Air hygiene: essential for our health

The fluid of 2 to 3 liters per day that we drink regularly contrasts with around 12,000 liters of breathable air that flows through our bronchi every day. We absorb more moisture through the latter than through the daily intake.

Woman breathes

So it doesn’t seem surprising that humidity and air hygiene are far more important than most of us attach to them. Anyone who has ever undertaken an introductory dive with a compressed air cylinder knows: 

The dry air we breathe not only allows the mucous membranes in the throat and nose to dry out , but also removes around 0.5 liters of fluid per hour from the body , which the scuba diver then has to compensate for with additional fluid intake in order not to dehydrate in the long term.

Before we dive into the basics of humidification, let’s take a closer look at the general health and physical properties of air first.

Not all air is the same: open air vs. indoor air

We differentiate between the properties of the air in closed rooms and in the open air. The negative air ions play an essential role in this . Negative ions, the so-called anions, reduce particulate matter and air pollutants. The high concentration of air ions in mountain and coastal regions explains why the mountain and sea air is said to have a cleansing and health-promoting effect

Since the negative ion charge in the air from higher altitudes also eliminates spores, for example, mold formation in the interior of houses in mountainous and coastal regions is rarely a problem.

City dwellers indulged in complaining about an air that lacks this positive, self-cleaning property. Fine dust and other air pollutants are a common problem that weakens the organism and its immune system . And that’s not all: The reduced active power of dry air in urban areas, for example, is directly related to the transport of oxygen: The aging process is accelerated and the probability of the transmission of infectious diseases increases: Viruses increase their activity in an environment with low humidity and spread in Increased indoor spaces. Especially in the cold winter months, this becomes a problem in closed rooms with several people, which should be prevented.

Optimal air hygiene in offices and interiors

We give a lot of thought to a healthy diet. Drinking properly and adequately is also a topic that many medical advisors devote themselves to. What is neglected, however, is the importance of our greatest consumer good – the air that surrounds us for most of the day and that we breathe for many hours.

Clean and healthy indoor air is characterized by two essential properties: On the one hand , it should be free of pollutants and pathogens such as microorganisms, germs and viruses. 

On the other hand , temperature and the directly related criterion of relative humidity are of central importance.

Relative humidity and temperature

D.he relative humidity is an elusive term for many. It describes the amount of water contained in the air in relation to the maximum amount of water that can potentially be absorbed.

Important to know : warm air can absorb more moisture than cold air. This explains why temperature and humidity are two inseparable and mutually influenceable criteria and factors for healthy air hygiene . People feel particularly comfortable at a room temperature of 22 to 24 degrees Celsius and a humidity of 40 to 60 percent.

If you finally consider that a temperature increase of just 1 degree leads to a decrease in the relative humidity of around 3 percent, you become aware of the relevance of the factors temperature and humidity . The reason for this physical adaptation process lies in the basic property of the air we breathe to store vaporous water up to the saturation limit.

Air climate and humidity – focus on health and wellbeing

M.Microorganisms are an integral part of our air. Our immune system even needs them to remain resilient and adapt to the pathogens and pollutants surrounding us and to effectively protect the organism. However, some of these surrounding organisms have the potential to damage our health if they are too high . Why a non-optimal humidity can pose a threat to our health is based on two mutually negative factors:

1. Intact, ie not too dry, mucous membranes are important for our immune system: Their self-cleaning function protects us from infections. If the mucous membranes dry out due to the long-term low humidity of the air they breathe, they lose their protective function and the risk of infection with an infectious disease increases.

2. Influenza viruses and other pathogens prefer on the one hand a particularly dry, but on the other hand also a particularly humid air climate. The unwanted organisms not only live longer if the humidity is optimal for them, but also spread demonstrably faster in so-called aerosol clouds. Dried out mucous membranes are less resistant and offer an optimal target for these viruses.

Investigations into the relationship between air humidity and health have forced an optimal range for the relative air humidity, which is of particular importance for health and for the risk of infection with infectious diseases in living and working spaces such as offices, practices or business premises. Especially in times of pandemics and flu waves, this is an important approach that many employers do not yet pay sufficient attention to:

The diagram shown above makes it clear: bacteria, viruses, fungi, mites and other allergens spread particularly well in a humidity level of 0 to 30 percent . While suspended particles and the risk they pose can be reduced to a minimum in an environment of 40 to 60 percent , the latter increases significantly again from a humidity of 60 to 100 percent

In addition to physiological effects, which manifest themselves in itching , dry cough and the general susceptibility to respiratory diseases , the psychological effects of poor air quality cannot be dismissed out of hand: motivation to work decreases, fatigue and exhaustion increase.

The findings lead to a far-reaching hypothesis by experts that investing in measures for air hygiene humidification could be far more sensible and effective than preventive interventions such as flu vaccinations. 

Air hygiene that is conducive to health could significantly reduce staff absences due to colds and the economic losses . Even assumptions about the positive influence of such measures on lethality in the context of influenza epidemics are justified in this context; according to statistics, more people die each year from influenza than from typical occupational accidents. 

The facts are telling: the costs for sick leave amount to more than 7,700 million euros per year . With this in mind, it is interesting that a third of the reasons for illness-related failure can be traced back to a disease of the respiratory system

CO2 pollution and significance for air quality

B.Especially in closed rooms where several people are present, the CO2 pollution is an important component, which is also discussed again and again from a health perspective. The CO2 content in the air is given in the unit ppm ( parts per million ). If the CO2 content of the indoor air exceeds the threshold value of 1000 ppm , the measures for indoor air hygiene and air quality should be checked and, if necessary, adjusted. Optimizing the ventilation behavior is often sufficient to achieve the desired effect of improving the air in the room. From 2000 ppmventilation is no longer enough. Experts from the Austrian Institute for Building Biology and Building Ecology therefore advise: In offices and work rooms, an air exchange of 36 cubic meters of air per hour and person should be ensured in order to guarantee a consistently high and harmless air quality .

People in the office

In order to achieve these recommendations, in addition to a change in ventilation policy, it may also be necessary to reduce the number of people in the room. Fewer people and more ventilation activities have a holistic effect on the quality of the indoor air climate: Not only the CO2 content, but also the relative humidity can be regulated and neutralized.

Professional air humidification as a multi-perspective approach to health protection

D.o Most people spend more than 90 percent of their work and leisure time indoors. If the air hygiene is inadequate and the air is dry, they are exposed to these health-threatening circumstances for many hours a day over the long term .

Ventilation systems are therefore used in many places. The goal: to improve health through better air hygiene. This should be achieved, among other things, by a greater exchange of air and a higher air circulation. The promising use may reduce the CO2 load, but the exchange of air does not necessarily have a positive effect on the humidity .

The integrated solution of direct room air humidification is advisable , but this only achieves optimal results if windows, doors to the outside and skylights are kept closed . Background : Cold, incoming air sinks down and causes unpleasant drafts. Entrained, humidified outside air is constantly transported outside by the heat pressure, before the optimal and desired humidity improves the indoor climate. Numerous solutions are already available for less than 1,000 euros without having to accept limited hygiene convenience.

Tip:Ventilation is and will remain important. Please note the general rules for ventilation: Intermittent and cross ventilation ensures a quick and effective exchange of air without negatively influencing the room climate and humidity in the long term.

Overview of the humidification processes

Passive humidification processes

P.assive humidification, which are mentioned in the context of a “home remedy lexicon” does not hold the what they promise. Everyone has probably heard of the recommendation to put damp laundry on the heater in order to enrich the room air with moisture. The efficiency of this effort: low .

In addition to the risk of temporary overhumidification , which can lead to the formation of mold , damp laundry only stores insufficient amounts of water to enrich the surrounding room air with sufficient and constant moisture over the long term. The same applies to the recommendation to hang water containers on the heaters, which also increase the risk of legionella and bacteria . Indoor fountains and plants are pretty home accessories, but they are hardly an effective means of enriching the air humidity.

Aerosol humidifiers

If aerosol humidifiers such as ultrasonic humidifiers , nebulizers or atomizers are used, thorough hygiene in the premises is essential: suspended matter, germs, bacteria and other pollutants attach themselves to the finest aerosols and become respirable. The result: allergy sufferers complain of complaints. 

Nebulizer next to window

Evaporative humidifiers heat the water until it evaporates and add a noticeable amount to your electricity bill. The evaporation technology uses 8 times the daily requirement of a conventional refrigerator. As with the aerosol air humidification technologies mentioned above, the released steam can make air pollutants lung-accessible. The high cleaning and maintenance requirements in everyday life should also be taken into account.

Direct evaporator – the natural humidification

As an alternative to the aerosol humidification devices , aerosol-free air humidifiers with direct moisture implementation are available. This technology category has air humidifier cartridges , air washers , cold water evaporators with Rieselbock and rotor humidifiers with air washer function and water disinfection.

Cold water evaporators with air humidifier cassettes suck dry air into the apparatus. Hygroscopic filter blocks draw moisture upwards through their capillary action and enrich them with moisture before they are returned to the circulating air.

Problems and disadvantages: The maximum performance of these air humidification systems is only achieved when the water level in the water tank is low. If the filter cassettes are calcified, they should be replaced promptly. Since the smallest air pollution collects in the filter system, care should be taken to ensure that this technology is hygienically used. Only designated chemicals, silver pens or special hygiene products are used for disinfection.

We recommend: direct evaporation with active water disinfection

The above-mentioned problems and disadvantages of the humidification systems with regard to the maximum possible hygiene, experts recommend aerosol-free direct evaporators with active water disinfection . These humidifiers, which are used especially in the office, have numerous advantages . The systems are mobile: there are no costs for installation or installation. An adaptation to the possibly changing requirements and demands of the office situation is also possible at any time without any problems.


Air purifiers in the ordination and in the waiting room

Cough – runny nose – flu time. The doctors’ waiting rooms are always well attended…. Whether at the general practitioner or the specialist: There are many people in the smallest of spaces. Influenza infections, flu viruses and also corona viruses are transmitted by droplet infection. The fear of infection in the waiting room is understandable. With the installation of ION-HEPA air purifiers, effective measures are taken in medical practices.

Waiting room with wheelchair

Those responsible also seem to have recognized the danger. That is why video consultation hours, online chats and digital waiting systems that notify patients so that they can take the direct route to the treatment room are increasingly finding their way into everyday practice. The goal: to relieve the waiting area. But the problem is not a new one and has been an increasingly pressing one since the emergence of severe flu will .

Measures against germs in the waiting room

In a conversation with a well-known newspaper, internist Burkhard Weimer explains the measures taken in other countries to reduce the risk of infection in medical practices as much as possible: In the United States, for example, flu tents in front of hospitals were used to shield infectious people . A measure that seems hardly feasible for individual practices on site for reasons of space alone.

Mother and child in the waiting room

In Austria, Germany and Switzerland, for example, infection rooms in children’s wards are a must in many places in the clinics.

The measures are being taken for a good reason: the medical professionals are aware of the risk of a possible aerosol transmission, i.e. virus transmission via the finest micro-droplets in the room air, which is enriched with virus DNA. 

A practical and at the same time efficient solution to permanently eliminate germs in waiting rooms was developed with the innovative air purification system of the ION-HEPA generation.

Relevance of air purification in medical practices

In 2014, the Competence Center for Hygiene and Medical Devices published guidelines for ensuring hygiene in medical practices. Anyone who carefully studies the recommendations will hear numerous instructions and recommendations – including that patients suffering from severe or contagious respiratory infections, including influenza and Covid-19 infections , should ideally be brought directly to the treatment room and from Practice staff should be equipped with appropriate mouth and nose protection. 

However, none of the listed hygiene measures address the equipment and hygiene organization in the waiting rooms . So there are no technical specifications – possibly also because there were hardly any suitable systems up to now.

Bioaerosols risk

Even those who have mastered the cough and sneeze etiquette can hardly prevent some of the up to 12,000 microfine bioaerosols that leave the human cough and throat area when sneezing from accumulating in the room air. 

According to the guidelines VDI 4252 Part 2 and VDI 4253 Part 2, the term aerosol is understood by medical professionals as a microfine suspended particle to which not only bacteria and spores but also viruses adhere.

The up to 0.1 nm fine particles evade gravity and float for several hours in the ambient air before they sink to the ground. This becomes a problem, especially in medical practices: the patient has long since left the practice, while potential viruses in the aerosols they emit pose a risk of infection for others , which cannot be stopped by washing hands or keeping your distance.

Drafts through regularly opening and closing doors as well as people standing up and sitting down distribute the aerosols throughout the entire room.

Those responsible in other everyday areas where the problem has already been recognized have reacted: Ventilation and air purification systems ensure virus-free air and a sustainable air climate that specifically deactivates active viruses and thus demonstrably reduces the risk of infection . Where central ventilation systems are not sufficient or are not suitable for retrofitting with appropriate filters, mobile high-performance air cleaning devices are installed.

Bivalent effect: air purification and humidity regulation

virus-free air

Modern ventilation technology in the doctor’s office has a bivalent effect on the spread of viruses and the risk of infection : The Scofield / Sterling diagram shows the importance of humidity for the spread of active virus DNA in the ambient air:

If the relative humidity is below the critical value of 40 percent, infectious bioaerosols remain stable in the air. The virus has a good chance of reaching a new host even above 60 percent humidity. 

The moisture concentrated in the air only has an antiviral effect on an optimal average of between 40 and 60 percent : proteins and salts from the surrounding humidity diffuse into the virus-contaminated bioaerosol and inactivate the active virus DNA , which consequently cannot trigger a new infection.

Air cleaning systems based on modern ION HEPA filter technology clean the ambient air and reduce air particles – continuously and fully automatically.   BUT: The optimal room humidity should not be forgotten! 


Many apartments are contaminated with mold – experts say that mold is 30-50%

In the WDR program “Household Check”, the building expert Andras Mollinger (graduate civil engineer) speaks of 30-50% mold-contaminated apartments in Germany. 

That frightening number seems even more terrifying given the health risks that come with mold. 

The mold pollutes the indoor air with the spores, which in turn are known to cause damage to health.


The causes of mold are water, moisture, moisture

Those affected by mold usually have no idea about mold, because it grows in secret (household check). The causes are very different. 

In the program, water damage was the first trigger for the mold in the affected family’s apartment. The rooms were renovated by the tenant after the water damage. 

When checking it, however, it turns out that the mold is deeper and the entire plaster of the ceiling has to be renovated. The wallpaper in the nursery had been re-wallpapered and the mold continues to grow behind the wallpaper.

Health hazards from mold

The family’s health was examined by Ivonne Willichs at the expert. The father noticed that the children had frequent colds. 

Mold forms toxins in the air in the room, which are inhaled and cause sleep disorders, fatigue, rheumatic damage, liver damage and initially have no connection with the home.

Measures against mold

What can you always do? The ventilation behavior must be optimized. Due to the high heating costs and the long time outside the home during work, ventilating one’s own four walls is often neglected. 

In addition, during certain periods of the warmer months, almost all cellars (but often other rooms as well) are exposed to increased humidity. The cause is the temperature difference between the outside air and that in the basement and other rooms. 

If you ventilate here frequently, you will also get a lot of moisture, because the warm air flows from the outside to the inside and condenses in the colder environment (cellar, …). 

Here you should constantly measure with a good hygrometer and you can counteract this with an electric dehumidifier. 

The dehumidifier ensures that the excessively high humidity is extracted from the air in the corresponding rooms and that it is reduced to a reasonable, adjustable level.

Even those who are healthy have to take care of moisture in order not to get sick

Of course, it can also make sense to call in an expert or to commission a room air analysis. Not only those who are frequently ill should have this analysis carried out or seek advice, but also those who are healthy can quickly become ill from mold in rooms.

We are happy to answer your questions about mold and moisture in rooms. Please ask us without obligation using the form.


Problem: Too high humidity in the swimming pool

Why should I dehumidify my swimming pool?

swimming pool

Evaporation on the pool surface increases the humidity of the pool hall to an unnaturally high level. 

The degree of saturation of the air often exceeds a reasonable level.

The result is condensation on glass fronts  and tiles, but also  mold behind cladding , on furnishings or in wall corners.

This often long-term, uncontrolled exposure to moisture leads to lasting damage to the building fabric, which can only be removed at enormous cost. 

However, it is not only immediately visible damage that results from excessive humidity: modern electrical and fitness equipment can be affected.

In addition, the excessively high air humidity impairs well-being and thus a real “feeling of relaxation”. 

That is why once beautiful bathrooms and wellness oases are no longer used and cause more costs and annoyance than joie de vivre.

The use of a high-performance  indoor swimming pool dehumidifier protects against costly moisture damage . A pleasant and healthy indoor climate in the swimming pool is guaranteed.


Air Purifier or Air Washer? What is better, what is useful?

Air Washer or Air Purifier?

Air washers and air purifiers perform different tasks – that is why a dedicated recommendation is difficult. In this report, the most important distinguishing features – and similarities – were evaluated

air purifier room

Air washer + air purifier – The air purification effect

Air purifiers work with 1 or more filters to filter air particles such as pollen, mold spores – or viruses from the air. Virus removal is only possible on devices with a high filter class. The humidity remains unchanged with this system.

Air washers, on the other hand, should both humidify the air and filter air particles. 
Filtration takes place in that the air particles are sucked in by a fan and washed out in a “water bath”.

The problem: just washing out and holding back particles in the water does not render them harmless. Many aerobic microorganisms cannot survive in water – but this method would be too risky without additional disinfection of the water. If you want to focus on air CLEANING, you should prefer an air CLEANER to an air WASHER.

How do air purifiers and air washers work?


With both the  air purifier  and the air washer, the room air is sucked in with a fan and directed into the interior of the device.

With the air purifier , the air flows through a filter (usually HEPA or EN1822). Very good air purifiers have active Hepa filters, which provide additional optimization of the performance.

I.In contrast to this, with the “classic” air washer, the air is passed over a stack of plastic plates that are wetted with water.

Air particles are washed out on these surfaces and collect in the water tank. The air purification function is not comparable to a “real” air purifier! Especially the smallest particles – those with the highest health risk – remain largely unfiltered.


Room air purifiers – the methods, the technology


In the case of air purifiers, there are systems that ionize air or eliminate odors using ozone. With activated charcoal attachments, gases and cigarette smoke can also be filtered.

Beware of ozone systems: Ozone is a reactive gas which, when overconcentrated, leads to headaches and can damage the alveoli. That is why very good air purifiers have an ozone safety test!

So-called ozone generators – which are often also offered as air purifiers – should only be operated with great caution. These devices generate ozone for air disinfection. This highly reactive gas breaks down organic compounds and renders many tiny particles harmless – but if the intensity cannot be regulated, serious damage to health can occur!

UV radiation-based air purifiers use the UV radiation wave to neutralize bacteria and viruses. The problem, however, is that the particles have to be exposed to UV light for a considerable period of time in order to be able to develop a sterilizing effect. In many devices, however, the air flows through the UV unit far too quickly – the majority of the germs are in turn distributed to the room air!

Io nisierende systems charge the air particles as it flows through special filter surfaces. The air particles are attracted as if by a “magnet” and stored in the filter fabric and eliminated. The combination of ionization and special ION-Hepa filters has delivered excellent results in CADR air purifier tests ! These procedures are used in the most sensitive areas (clinics, laboratories) and are in the price range of several thousand euros. The system has been adapted for office and living space users. In “air protectors” professional air purification is made available at an affordable price for kindergartens, offices, living space, ordination.

Now to another topic: If you don’t just want to clean the room air, but HUMIDIFY it, humidifiers and air washers are used. Increasing room humidity means taking preventive measures against the health threats of dry air!

Air washer – humidify and remove air particles

A distinction is made between two technologies for air washers: Devices that humidify using a stack of plastic panes – the “classic” air washers. And those that work with large “filter surface rotors”. Due to the large surface, larger rooms can also be supplied.

L.Air washer models with plastic disc evaporation require an additional fluid to change the surface tension of the water. Otherwise the water “rolls off” the plastic panes and can only contribute marginally to the humidification. These additives can, however, contain preservatives, which get into the air with the water particles and are inhaled…. In addition, it must be taken into account that the permanent aeration of the water surface means that there is a risk that germs will be blown away from the surface. Air washers with HEPA filters have recently become available. It should be noted that the filter class should be H14. H13 is often used. H13 is sufficient for dust washing – but if z. B. Viruses are to be eliminated EFFECTIVELY, H14 is the “measure of all things”!However, Hepa 14 has a significantly higher air resistance and would require powerful fans. That is why you will rarely find a HEPA14 filter in air washers …
But the difference is tremendous:
HEPA14 has a transmittance for particles of less than or equal 0, 0 25%
HEPA 13 has a transmittance for particles of less than / equal to 0.25%.
That means – ten times more particles can overcome the filter barrier in an H13 filter !
Especially with the smallest particles – viruses – this is THE decisive factor! Therefore: Pay attention to the HEPA14 filter.

E.Another type of air washer is the group of direct evaporators. With these systems, the air is “washed” using special filter fabrics.

A distinction is made between systems with a block filter and a rotor humidifier. In the case of the block filter variant, the dry air is passed over the wetted trickle block with a fan.

B.In the rotor humidifier, a drum impeller with a fine knitted filter fabric and a very large filter surface serves as the evaporation medium. This drum wheel rotates permanently in a water bath. The fan transports the dry room air over this “sponge”. The dry air is enriched with moisture.

Air washer – pay attention to the correct water disinfection!

Chemical-free disinfection methods are used in the water tank for both trickle block humidification and the rotor humidifier. From mineral filters to UVC disinfection – which has been tried and tested in drinking water technology for decades.

Beware of chemicals (chlorine preparations) and disinfectants that act as “water fresheners”. Although they are easy to use, there is a risk that these substances will evaporate through water evaporation and be released into the room air – this can be problematic for the respiratory system, especially in the event of overdosing. If the dosage is too low, the water will not be adequately sterilized….
Since some bacterial strains have developed resistance, this water chemistry may even remain ineffective …

Metal pins with a silver coating (argent pins) are easy to use, but have to be replaced at relatively short intervals because they wear out.

Salt would be the most cost-effective way of disinfecting water – but this is countered by the fact that this would result in a massive reduction in the lifespan of the humidifier, which would in no way be an economically viable measure.

Using UV water radiation lamps for disinfection has the advantage that the bacteria cannot develop any resistance to it. There are no mistakes in dosing – and there are no emitting chemicals either.

Conclusion – air purifiers versus air washers:

Air purifiers reduce allergens and fine dust – and thus support the health of allergy sufferers and asthmatics.

Air washers prevent dry air and thus counteract dried out mucous membranes. They reduce eye irritation and dry skin. Depending on the system, air particles are also eliminated – but an antiviral effect cannot be achieved with standard air washers.
The problem of many air washers: “Not fish / not meat”. Too inefficient to clean the air – Too inefficient to humidify the air. Make sure that the air washer has a humidification performance specification – this is the only way to actually compare different models. If this information is missing, it can be an indication that the humidification performance is only marginal.

C.onclusio: If you want to achieve comprehensive indoor air hygiene, you should PRIMARY pay attention to the correct room humidity . Optimal room humidity reduces the survivability of viruses and lowers the risk of aerosols spreading.
Air purifiers should be positioned as a supplementary measure. Its purpose is to remove germs and viruses through intensive filtration. Remove bacteria from the air.
1. Prevention of dry room air by installing air humidifiers.
2. Active reduction of airborne particles through air purifiers.


Viruses & dry air – with THE.PURE for optimal room air and humidity

Air purification Viruses humidify Air purifier-humidifier air washer

Dry indoor air in winter – and the flu season is just around the corner ….
In 2020, there will be an added complication that Corona uses a similar spreading scheme as influenza viruses. Eliminating dry air and improving air quality is the order of the day.

Before Covid19, little attention was made about viral diseases. But the fact is: Viruses are one of the greatest threats to our immune system! The perfidious: The threat takes place where we do not expect it: In living rooms, in the office – and generally in all closed rooms! In the 2017/2018 flu season alone, excess mortality in Germany was over 25,000! Persons! And that is only an estimate – because there are no comprehensive studies for virus flu deaths in the long term!

So what could be more obvious if we try to protect ourselves better against viruses in the future! Mouth and nose masks are useful – but not a permanent solution – not for years to come. In addition to hygiene measures such as hand washing and more mindfulness with direct contacts, one factor is very decisive: ROOM AIR!

How many hours do you spend outdoors – and in relation to this: How many hours do I spend at home or at work? How important is it to me that this room air is as free as possible from viruses, pollen and other health problems? Contents:

How can you protect yourself against viruses?

In addition to the known measures and hygiene recommendations, one topic is given far too little attention: the optimal room humidity reduces the health risk!

What effects does dry air have on viruses and the risk of infection?

Many research results over the past decades have shown that room humidity plays a decisive role in the spread and aggressiveness of viruses. These results document the relationship between humidity and temperature – and their effect on virus resistance. The result of all studies:

The risk of virus infection increases in dry air because the viruses can survive longer!

Laboratories around the world have researched the SARS pandemic to study the survival times of viruses on surfaces and in the air. 

The result: Virus activity, i.e. the risk of infection, is significantly higher in dry air than in optimally humidified room air!
At the beginning of the Covid virus pandemic, the focus was primarily on surface transmission and then on droplet transmission – studies are gradually showing that the survival time of viruses in closed rooms is more problematic than outdoors. Why? Among other things, because the air humidity in rooms usually corresponds to a value that is optimal for viruses – but not for human health….

Pay attention to your room humidity!

Measure and monitor the humidity situation in your rooms on a regular basis. Especially in the office, values ​​are often reached that can be problematic.
In order to evaluate the room humidity, experts recommend the use of room humidity meters.
The humidity meter Black Edition from WD-AUSTRIA has proven itself particularly well  : room humidity meter

Hygrometer for measuring humidity

What room humidity should I have in the office / at the workplace / in the children’s room / in the apartment?

The guideline value is around 45 to 55%. Whereby the hazard risk is to be assessed as high, especially below 30% RH. If you want to know more about the optimal humidity in the office – living room – children’s room – workplace – contact our team of humidity experts!

Hygiene rotor humidifier: The proactive preventive measures against viruses

How can I ensure healthy indoor air? How does the removal of dry air affect the virus?
Pay attention to optimally humidified air in work and living rooms – and thereby reduce the activity of the viruses! In general, optimal humidity has a positive effect on the defensive function of the respiratory tract – and supports your immune system! Hygiene rotor humidifiers and air purifiers with high CADR test values
are suitable for this . Humidify and purify air – to protect your health and your family!

Questions on the subject – Eliminate virus by purifying air and humidifying the air?

Do you know ….. How do you eliminate the virus and dry air?
Do you know … .. which humidifier is suitable for your area of ​​application? 
Do you want to know …… Why do so many humidifiers mutate into germs?
Why don’t many air purifiers work against viruses – we are useless? 
Questions to which we would be happy to send you an answer.
Contact us
– we are very happy to be at your disposal! 


Why is it necessary to dehumidify rooms?

What does “relative humidity” mean?

Air always contains invisible water vapor. “Relative humidity” (RH) is the water vapor content as a percentage of the maximum possible (at a given temperature). The maximum possible absolute water content (i.e. 100% RH) is, however, strongly dependent on temperature: at 0 ° C it is approx. 4 grams per m 3 of air, at 10 ° C approx. 8 grams, at 20 ° C approx. 15 grams and at 30 ° C over 40 grams per m 3Air. So: the warmer the air, the more water it absorbs. This property of the air is also the reason why the dehumidifying performance of the dehumidifier increases so much with increasing temperature. From this it is also clear that water can be removed from the air by cooling. When the air temperature drops, a state is reached where the relative humidity exceeds 100% and the excess water is excreted. This temperature is called the “dew point temperature”. In nature, fog or dew then arises, in the dehumidifier the water condenses on the evaporator and runs into a bucket.

Measure humidity with the hygrometer

Hygrometers for displaying the relative humidity are available cheaply in do-it-yourself shops. However, they should always be “calibrated” first according to the instructions. This is how you do it: Wrap the hygrometer in a damp cloth and set the device to approx. 98%. Even the more expensive hair hygrometers should occasionally be checked and regenerated and, if necessary, adjusted.

When is it too wet or too dry?

Humans normally have no problems with very high (fog) or very low (beautiful winter day) relative humidity. The recommendation to keep the relative humidity at 30 to 60% in living rooms is more due to side effects: below 30%, the dust raised by the heater often irritates the respiratory tract. Above 60% relative humidity in the room, the local humidity is significantly higher on cool surfaces and can promote the growth of mold. Incidentally, in summer the relative humidity is quite often around 70% or even more. In the absence of “cold corners”, however, there is hardly any risk of mold. Then dehumidifying the room air in the apartment makes little sense. Conversely, it is often humidified in winter in order not to risk a “dust-dry” throat.

It looks a little different for sensitive stored objects – especially in the basement. Organic materials such as paper, leather or textiles, with a relative humidity of over approx. 75%, offer advantageous growth conditions for decomposing bacteria and fungi, which can usually be observed as mold. In addition to the decomposition of the material, a musty smell is often perceived as annoying. Therefore, in places where sensitive materials are stored, the humidity should be limited. On the other hand, high humidity is welcome in other basement rooms, for example in the vegetable store. Since the moisture can also migrate (diffuse) more or less well through walls, it is hardly possible to have reasonably dry storage rooms next to a (more humid) natural floor basement.

Causes of excessive humidity

Most of the cellars are partly in the ground. Because the soil is usually quite damp and normal concrete does not really seal off moisture, there is natural moisture ingress in such basement floors. In old buildings with rammed concrete or natural stone walls and especially with natural floors, even a lot of moisture can penetrate. This can be particularly strong with standing water (“slope pressure”) and insufficient or blocked external drainage (seepage pipe). At most, strong ingress of moisture can also be caused by leaks in water or sewer / roof water pipes. Such structural deficiencies should, however, also be remedied by structural measures and not compensated for by energy-intensive dehumidification.

Other possible sources of moisture are:

  • damp laundry, also other damp objects
  • plants
  • Humans or animals (they exhale moist warm air)
  • Showering, bathing, cooking.

Expel moisture by ventilating?

In our climate, the humidity in apartments or heated rooms can usually be kept sufficiently low by correct ventilation: if necessary, briefly cross-ventilate several times a day. Therefore, dehumidification is usually not necessary. In rooms with comfort ventilation systems, air that is too dry can be a problem in winter.

It is somewhat different and, above all, more difficult in basement rooms. Because these are not heated, even a small amount of moisture is sufficient to increase the relative humidity. Ventilation can even be counterproductive here, namely when the outside air is warm and humid, which is especially true in spring and summer. Continuous ventilation is also problematic in winter: because it cools down the basement rooms and even a small amount of moisture leads to a strong increase in the relative humidity. Basement rooms should therefore be specifically ventilated when the outside air is as dry as possible, and as in apartments, short burst ventilation is most effective.

Measures against excessive cellar humidity

Before you buy a dehumidifier, you should clarify possible sources of moisture and, if necessary, eliminate them, for example flush clogged drainage pipes and possibly install moisture insulation on the outer cellar walls in the ground (time-consuming!). The use of an air dryer can also help to dehumidify the neighboring rooms. Targeted ventilation of the basement rooms can also reduce the humidity (burst ventilation when the outside air is dry).

A dehumidifier should only be considered if a temporarily high humidity cannot be accepted. Be it because sensitive materials have to be stored or when mold even grows on walls. To choose the correct device size, see below.

How do dehumidifiers work?

Air dehumidifiers for room temperatures above approx. 10 ° C and relative humidity above 40%, as presented by Topten, work according to the condensation principle (heat pump principle): The moist air is sucked in and cooled down so much by the heat pump evaporator that the water is excreted (condensed) from the air. The dehumidified air is then reheated in the heat pump condenser and blown back into the room. The condensed water is collected in a water tank or fed directly to a drain using a waste water hose.

The same functional principle is also used in room air tumble dryers, which, however, have a stronger fan for intensive air circulation in the drying room.

  1. Evaporator (cooling)
  2. Condenser (heating)
  3. fan
  4. compressor
  5. Water tank
  6. moist air
  7. dehumidified air

Operation, maintenance

All dehumidifiers on have an energy-saving hygrostat control. The device switches off when the set room humidity is reached and on again when it is exceeded. A float switch prevents the water tank from overflowing. Maintenance is hardly required; At most, an air filter should be cleaned occasionally, especially when operating in a dusty environment and with room air dryers (fluff).

Optimal device size

Determining the device size is important for the desired dehumidification effect, but also for the resulting power consumption. A device that is too small cannot reduce the humidity to the desired extent despite continuous operation. A device that is too large, on the other hand, only remains switched on for a short time because the air humidity drops very quickly below the switch-off value. The many switching on and off processes reduce the efficiency. How can you determine the optimal device size?

1. Room volume

Because the actual amount of moisture is usually difficult to estimate, a first clue can be obtained about the room volume to be dehumidified and the relevant room temperature (here indicated by the area, assumption 2.3 m room height):

  • Up to approx. 70 m² (eg 3 to 4 larger basement rooms) a device of the class “up to 8 liters / 24h” should be sufficient at 15 ° C.
  • If more or larger such rooms or approx. 70 to 200 m² are to be dehumidified (doors open or only grids), a larger device, up to 16 liters / 24h, should be used.
  • If significantly more than 200 m² are to be dehumidified, a device with more than 16 liters / 24h dehumidification capacity is required.

Attention: This information applies to 15 ° C; At 10 ° C only about half of this area can be dehumidified, at 20 ° C, on the other hand, almost twice as much.

2. Take into account the occurrence of moisture

The following factors are signs or causes of a higher moisture load, which require more detailed clarifications and possibly other, e.g. structural measures or possibly a higher dehumidification performance:

  • The basement walls are sometimes damp or black-gray mold can even be seen on the masonry. However, such cases should be clarified by a building physics specialist; the moisture supply may have to be structurally reduced (e.g. drainage pipe / sealing outside).
  • Damage to organic material such as paper, leather and textiles occurs regularly. However, such goods should not be stored in a rather damp cellar; the power consumption for strong dehumidification can cost a lot!
  • Partly natural soil (pounded earth, gravel). Such a floor was originally designed to keep the room moist, especially for storing vegetables and fruits. Instead of wanting to dry such rooms with a lot of power consumption, it is better to convert the floor (concrete, waterproofing).
  • Occasionally, laundry is hung up to dry; a room air dryer is not available. Smaller / medium-sized dehumidifiers are less efficient than room air tumble dryers. You can therefore only reduce the room humidity again in the long term. If laundry is dried regularly, it is better to use a room air dryer instead of a more powerful air dryer (see Topten section on household appliances).

3. Room temperature (decisive for use)

If the room temperature of the room to be dehumidified deviates significantly from 15 ° C, you should absolutely observe the dehumidification capacities at 10 ° C or 20 ° C, which are also given in the Topten list: they can deviate significantly from the 15 ° C values. Attention: The efficiency classes are determined at 15 ° C; Even well-classified models can therefore perform much worse at lower temperatures, for example when the dehumidification performance is much lower there.

The dehumidification performance is strongly temperature dependent

As the room temperature falls, the dehumidification performance decreases significantly, which is why the performance values ​​at 10 ° C must also be taken into account when using in very cool rooms (e.g. basements). On the other hand, when used in heated rooms, the values ​​at 20 ° C are decisive. The temperature dependency can, however, be quite different from device to device. It is therefore worth taking these values ​​into account if the planned use is mainly below or above 15 ° C.

Note the noise level

Depending on the place of use, the noise level can be important: in apartments, 50 dB (A) can be heard well, while values ​​above 60 dB (A) are not annoying in a basement with little traffic.


Room air purifiers – useful technology in the fight against Corona Covid 19 and flu viruses?

Everything revolves around THE topic these weeks:
air purifiers & HEPA filters. But – what’s the point?

Room air purifier – HEPA14 – UVC – ANTIVIRAL FILTER – Air purification
Most of the terms – and not even the topic itself – hardly moved anyone until three months ago…. And now – ROOM AIR CLEANING is on everyone’s lips….

Covid19 has caused a “run” on air purifiers. The producers – at least the high-quality devices – have weeks of production time. The prices of some models have risen by 40% in four weeks … No investment should be too high for your health. But what’s the point?

Air purification devices – technical necessity or “much ado about nothing?”

A basic distinction must be made between rooms with and rooms without a ventilation system.

In the presence of highly qualified exhaust air systems – as is common in modern office buildings – the virus load will never reach the same level as in non-ventilated rooms.

The air purifier discussion originally developed out of the requirement to protect restaurants and classrooms from viruses. So – large rooms – with many people – in a confined space.

By making the population aware of this issue, the demand for HEPA14 ANTIVIRAL FILTERS in the office was of course also made. After the first phase of the “must-have purchase”, the first critical voices are now emerging.

In the meantime, it is considered that installing an air purifier creates a feeling of security. A feeling of security that is usually a deceptive one. What is not taken into account: Dry office air – and this has been a latent health problem in many offices for many years – promotes exposure through the viral load !

If “air purifiers only” are positioned without removing the dry air – the circulation of the dry air may cause an undesired effect …

(See the report  Aerosols: Small-but- “powerful”)

The discussions for / against HEPA or UVC air purifiers distract from the actual topic: 

What measures can be taken to reduce the viral load and the infectiousness?

A virus cannot stay in the room for very long, especially in rooms with ventilation options – it is extracted via the exhaust air. 
It is much more important that the freedom of movement of the virus is restricted as long as it is in the room – and for this you need: humidified air

Room air purifier in the office
Room air purifier with active HEPA filter

Due to the focus on room air purifiers and the discussions about which filter system is the best, the  essential aspect for preventive health protection is completely lost: Our organism needs a room air humidity of 45 to 55%!

Air that is too dry in particular puts a strain on the body and weakens the body’s defenses and our immune system – we become susceptible to attacks by pathogens – especially viruses!

What effects does room air humidity have on viruses?

Dry air: viruses are active. Aggressive. Have full infectivity. Can be widely distributed. Humidified air: Viruses are sluggish – and the infectivity is clearly limited.  One has – justifiably – ask the question: Would it not make more sense FIRST spaces moisturize optimally ? Only then to think about whether room air purifiers can ADDITIONALLY improve the situation?

Air purification makes sense – not only during virus times, but all year round. 
Fine dust – mold spores and many other air particles cause at least as large a number of seriously ill and fatal victims as the Covid19 virus….

The decisive factor , however, is to prevent dry room air in order to restrict the mobility of aerosols – and thus the means of transport of the viruses! The “aqueous” part of the aerosols / droplets evaporates in dry, warm room air. The aerosols / droplets shrink, become lighter – and stay in the air longer …. Experts recommend: “It is therefore important not to let the relative room humidity drop too much, otherwise the particle survival time is increased!”.

From this point of view, the current “necessity questions” about air purification are to be seen as justified…. Air purification is an instrument that is definitely to be welcomed as an additional measure.

And there are also very good devices, such as B. the HEPA air purifier from Hummel + Mann (approx. EUR 2,000.00 + VAT) or the room air filter GRAN900 (EUR 900.00 + VAT).

Make sure, however, that the air purifier devices have filters that actually remove viruses ! There may hardly be a difference between HEPA14 and HEPA13 – but in practice the discrepancy is glaring! 

With a HEPA13 filter, the air has to be passed through the filter significantly more often in order to filter particles out of the air. Hepa 13 is sufficient for “normal” air washing – but if the focus is on reducing viruses – then H14 should be the minimum standard.
To explain:
HEPA14 has a degree of penetration for particles of less than or equal to 0. 0 25%
HEPA 13 has a degree of penetration for particles of less than / equal to 0.25% – i.e. ten times more particles that pass the filter!
Especially with the smallest particles – viruses – this is THE decisive factor!

For this reason, some air washers that are equipped with simple Hepa filters are not to be classified as virus air purifiers. At best, the filter can be viewed as an additional application for air washing. If you want to “CLEAN air”, you cannot avoid a “real” air purifier.

Which equipment criteria should an air purifier have?
Why are simple air purifiers with HEPA13 / HEPA14 filters much too loud for practical use?
Pros and cons of UVC ozone filters.
Soon available in the room air hygiene configurator on the subject of room air filters

room air purifiers make sense – room air cleaners are helpful – and high-quality models are also extremely effective. BUT: The “around and on” must be to generate healthy indoor air humidity

Please pay attention to your room humidity : A humidity corridor of 45 and 55% RH is considered to be “virus-hostile”. The absolute minimum value should never fall below 40% RH


Water damage in the basement – drying a damp wall and floor

Water in the basement – drying wet walls and damp floors

Regardless of whether it is a broken pipe or a flood: water causes damage that has a lasting impact on the building fabric. Above all, ceiling and false ceiling cavities, screeds, insulation in walls and flat roofs are particularly at risk from water damage. Blotchy paintwork, mineral efflorescence, decomposition of the building fabric, peeling tiles and the swelling of floors are the result.

Furthermore, unpleasant smells, as well as the formation of fungus and mold, can result in health-endangering consequential damage that severely impair the quality of living and living.

What should you watch out for when drying wet walls and floors?

The following parameters are decisive when damp walls and floors are to be dried:

  • total area
  • Number of rooms affected
  • Room height (normal room height, open construction or industrial hall)
  • What triggered the damaging event? (Burst pipe, flood, etc.)
  • Is there an insulation layer under the screed?
    If so, what material? (Impact sound plates, glass wool mats, expanded clay fill)
  • Floor covering (tiles, parquet, carpet, etc.)
  • Is there underfloor heating?
  • How long ago was the water ingress?
  • Which impairments are visible? (rising soil moisture, mold, etc.)

How long does it take to dry after water has entered?

The drying time depends on the amount of water that has penetrated, the type of insulation and the size of the drying area. Using a number of devices that is suitable for the size of the room, a drying time of about 1 to 3 weeks can be assumed. If the drying time is too short or the number of devices is too small or the drying methods are inadequate, consequential damage is inevitable. In the event of water ingress due to flooding , a longer drying time is to be expected.

Insulation layer drying process for dehumidifying wet floors

After water damage and flooding, it should be determined whether the moisture has penetrated the insulation or screed. Superficial drying with building drying devices is not effective in this case, as the moisture has already penetrated the building fabric and can permanently damage it. The result is mold and bacteria formation below the screed. By installing surface dryers alone, the insulation layer cannot be dried – the moisture under the screed can only be removed by using an insulation drying system.

Water damage pressure method with screed drilling

Before the actual start of the drainage process, holes with a diameter of approx. 50 mm are made in the screed – the number of holes varies depending on the size of the room and the humidity. Inlet nozzles are placed in the holes in the screed. Air hoses are attached to the insulation turbine, which is placed in the affected room, and are connected to the nozzles in the screed drill holes.
Dry air is now transported into the insulation layer via this hose system. This creates an overpressure in the insulation level. The dry air removes the excess moisture from the insulation material and flows back over the screed edge strip into the room, where it is absorbed by drying devices.


  • Low equipment costs


  • Uncontrolled leakage of decontaminated, moist air
  • Germs and mold spores that have already settled in the insulation level are blown unfiltered into the room air.
  • Drilling will destroy the floor
  • Uneven drying / formation of corridors

Water damage vacuum method with screed drilling

In the vacuum process, the system is reversed: The insulation layer turbine sucks in the moist air from the insulation level via the hose system. A vacuum is formed in the insulation layer – dry room air flows over the edge of the screed edge and in this way is enriched with the moisture in the floor.
The moisture sucked in by the turbine is passed through a special filter system, cleaned and either released into the room air or diverted to the outside via a hose system.


  • Low equipment costs
  • Special filter system removes germs and mold spores
  • Moist air can be cleaned and transported outside via a hose system


  • Drilling will destroy the floor
  • Uncontrolled air flow – remote side areas may not be adequately dried
  • Uneven drying / formation of corridors
  • Depending on climatic conditions

The vacuum method with screed-floor-edge joint nozzles

With this water damage drying method, edge joint nozzles are positioned instead of the screed drilling, which are installed along the wall sides.
The drying turbine sucks in moist air from the insulation level – a negative pressure is created. Dry air flows in over the screed edge joints, accumulates with the excess moisture in the insulation layer and is absorbed by the turbine via the edge joint nozzles. After drying, the air is filtered and then either used for the next drying process or discharged outside.


  • Low equipment costs
  • Special filter system removes germs and mold spores
  • Moist air can be cleaned and transported outside via a hose system
  • Edge joint drying system – screed drillings and interventions in parquet and tiled floors are avoided


  • Uncontrolled air flow – remote side areas may not be adequately dried
  • Uneven drying – possible residual moisture
  • Depending on climatic conditions

The (almost) non-destructive floor drying with edge joint nozzles

One or more air drying devices are positioned in the room to reduce the humidity.
A vacuum drying system is installed to remove moisture from the insulation level. Edge joint nozzles, which are connected to the hoses of the vacuum drying system, are positioned along one side of the wall between the screed and the wall.

The humid air is sucked in via the hose system and fed into the vacuum drying system. There the humid air is dried, passed through a special mold filter and then cleaned and released into the room or sent directly to the outside via the hose system.

In order to guarantee even and comprehensive drying, a controlled post-flow of pre-dried air is necessary. For this purpose, edge joint nozzles are also installed on the opposite side of the wall. The pre-dried and sterilized room air is fed to the dry air system, compressed and then fed into the edge joint nozzles. Dry air flows into the insulation level and is enriched with the excess moisture.

With this method, the pressure side of the water damage drying system is selected to be more powerful in order to generate a negative pressure in the insulation layer. This system application prevents emissions along the edge of the screed!

When using the system, when the dry air is introduced, a biological agent is introduced into the insulation layer to ensure decontamination of mold and putrefactive bacteria. This active ingredient is absolutely harmless and enables unhindered use of space.
Thanks to the long-term depot effect, germs that arise with every entry of water are comprehensively and sustainably eliminated!


  • Expensive floors are preserved
  • Germ elimination with long-term depot effect through biologically active ingredients
  • Special filter system removes germs and mold spores
  • Moist air can be cleaned and transported outside via a hose system
  • Controlled air flow enables even drying
  • No corridor formation due to the support vacuum principle

Hollow construction and insulation layer disinfection – The active ingredient:

In order to avoid health problems caused by emissions and corrosive / aggressive side effects of toxic agents such as chlorine or hydrogen peroxide, citric acid, formic acid, the non-toxic polymer preparation “Biodesinfection50” is recommended.

Broad spectrum effect: fungicide / algicide / bactericide / virucide

This active ingredient is also used, for example, for disinfection in hypersensitive areas such as hospitals and is also used in the food and meat industries: even legionella and listeria are eliminated by the active ingredient. Due to the composition of the preparation, there is no development of resistance!

The use of mold filter systems for dehumidification after water has entered

With standard drying processes, the suctioned insulation layer air must be discharged to the outside in order to avoid contamination of the room air with any mold spores. However, this air discharge causes enormous heating energy costs because several hundred m³ of room air have to be replaced with fresh air every hour. In addition, the air mostly flows in through windows and doors and, depending on the weather, may be more humid than the room air itself….

Another problem: If the air is conveyed out of the affected room without filtering the airborne germs, adjacent apartments are threatened by the pollutant particles.

That is why the use of mold filter systems HEPA14 is recommended for water damage restoration. The vacuum air from the cavity drying is conveyed in a controlled manner into a filter module – dirt particles, mold spores and germs are retained and the cleaned air is fed into the drying process.