General information on mould

Mould refers to filament-forming fungi. The set of filaments is called the fungal mycelium, which represents the actual fungus as an organism. To maintain the organism, spore carriers grow from the mycelium in certain situations. Depending on the genus and species, these carry a few to thousands of spores. The spores are released into the room air and reach other surfaces with air currents. There they wait for favourable conditions, germinate and form a new fungal mycelium, which in turn forms spore carriers, and so on.

First and foremost, mould needs moisture. The other necessary factors like light, oxygen, nutrients, ph-value, etc. are usually optimal or at least sufficiently present in our habitats. Therefore, moisture is the limiting and most important factor.


Mould occurs everywhere because it is a necessary part of living nature. For example, as saprophytes, fungi break down organic material (dead plants, trees, etc.) and release their nutrients to the soil, which in turn can be used by growing plants.

Indoors, mould is usually found on food (cheese, bread, sausage, drinks). But it also occurs on other organic materials such as acrylic sealant in the bathroom, on plastics, textiles and even on windows. There, the mixture of humidity, fatty acids (cooking fumes) and house dust has created a sufficient breeding ground.

Mould in your home?

Mould in the house! As useful as mould is in nature, in the home it can be a health hazard. Depending on the type of moisture damage and its cause, it either grows visibly on the walls or hidden behind panelling and wallpaper.

Indoors, especially in the living room and bedroom, a certain concentration of mould spores in the room air should not be exceeded. This is because mould spores and hyphae can cause all kinds of illnesses.

These include constant fatigue, itchy or burning eyes, respiratory complaints and even bronchial asthma. But chronic exhaustion, intestinal diseases and other symptoms are now also attributed by medical experts to possible contamination of indoor air with mould spores.

Damp wallpaper due to insufficient ventilation of rooms, improper heating behaviour, structural or material cold bridges, as well as building and water damage are the most common causes of mould infestation in living spaces.

The real problem with mould, apart from the damage to affected materials, is the way mould reproduces. It reproduces by forming spores in the air. Species like Aspergillus or Penicillium release millions of them into the (room) air. In other species, the spores attach themselves to a slime matrix and are only released poorly or in relevant quantities when the fungus dries (this is particularly important to bear in mind in drying measures). Along with room air, these mould spores are inhaled by people and can cause allergies, skin rashes, asthma and other physical symptoms.

Suspect mould?

If you suspect that your flat or property is infested with mould, we can detect or rule out mould infestation through a humidity and mould inspection. Suspicions always include a musty smell or discolouration of wall surfaces. Depending on the cause, implementing simple measures can already prevent the infestation from spreading and re-forming in the long term.

Moulds are very frugal when it comes to their environmental conditions. The cellulose in the wallpaper, the carbon from the silicone seals on the edge of the bath, the soap residue in the tile joints of the shower serve as food for them. Even the little dust that settles on walls and windows over time is sufficient as a source of nutrients. Mould needs no light, no heat and hardly any oxygen!

But what it does need is moisture! Therefore, this most important factor must be eliminated!

Mould is sometimes found in combination with bacteria, mostly actinomycetes. Since bacteria need more moisture to develop, they usually do not multiply in the case of moisture damage due to condensation, but they do multiply in the case of water pipe leaks or a continuous inflow of moisture from outside, e.g. inadequate moisture barrier on exterior walls. Like some fungi, bacteria also produce toxic metabolic products that they release into indoor air, contributing to additional pollution of the air we breathe.

Toxicity of mould

Concrete statements on the health effects of mould on humans are currently not possible. The pathogenic potential of individual mould species is too different, the sensitivity of the inhabitants too heterogeneous.

Moreover, only certain species of mould are capable of forming and releasing mould toxins (mycotoxins) into indoor air. The time and amount, and especially the necessary room climate parameters, at which mycotoxins are formed are often insufficiently known.

The best known is the group of so-called aflatoxins, which are classified as carcinogenic. It is these fungal toxins and other metabolic products that can cause physical symptoms such as headaches, diarrhoea, lack of concentration, etc.

Some moulds can cause infections (e.g. Aspergillus flavus, A. fumigatus) and under certain circumstances also damage the human organism (aspergillosis). Other fungi can only do so if they encounter a very weak immune system in humans, as is the case, for example, after organ transplants.

Moreover, all types of fungi have a more or less strong allergenic potential, which is an important factor in the development of asthma.

In case of suspicion, it therefore makes sense to carry out a mould testing in the flat, especially the sleeping area.