neutralising formaldehyde

Prevention and renovation:

We spend most of our lives indoors. On average, that's about 20 hours a day. Our indoor air should therefore be as pure as possible. However, hidden pollutants are often concealed behind seemingly health-conscious building plans. There are many reasons for this: wrong choice of building materials, failure to observe drying times, air tightness, putting the design and appearance of a space before health and safety standards, ... One of these pollutants that can make people ill when present in high concentrations is formaldehyde.

What is formaldehyde?

Formaldehyde (pronounced from-aldehyde) is an organic compound and is one of the most important organic basic substances in the chemical industry. It is used in a wide variety of areas, such as building materials, dyes, medicines and textile finishes. It is therefore not surprising that it is also found indoors. Wood materials such as chipboard, floor coverings or even furniture can contribute to increased and harmful concentrations.

At room temperature, formaldehyde is gaseous and free formaldehyde dissolves from objects. This substance is also known as formic acid aldehyde, methanal or oxomethane. In the group of aldehydes, it is the simplest, as it consists of only one aldehyde group (CHO) and one hydrogen atom (H). The structural formula of formaldehyde is therefore CH2O.

Its chemical properties up close:

  • Its physical state is gaseous
  • It is very soluble in water due to its molecular structure
  • In dissolved form it is known as formalin
  • Its melting point is -117 degrees Celsius
  • Its boiling point is -19 degrees Celsius
Measure formaldehyde concentration Measure formaldehyde concentration
How can I measure a concentration of formaldehyde?

There are now various measuring devices on the market that can determine formaldehyde levels in indoor air in real time. The measurement is usually carried out via an electrochemical sensor to which the molecules dock.

The exact formaldehyde concentration can also be determined in a laboratory. To do this, the room air is usually drawn into a test tube for 30 minutes. Air pressure, humidity and temperature are documented. The air in the test tube is then analysed in detail in the laboratory.


Is formaldehyde poisonous?

Formaldehyde is toxic to humans and animals, and above a concentration of 30 ml/m³ it can become life-threatening. Since 2014, formaldehyde has been classified as carcinogenic throughout the EU. A guideline value of 0.1 mg/m³ applies indoors.

However, even at concentrations below this guideline value, this residential toxin causes irritation of the mucous membranes of the eyes and respiratory tract, or headaches for some people. Most irritations are only temporary, but allergies can easily develop. Disinfectants containing formaldehyde must be labelled accordingly according to the CLP Regulation, with a warning such as "may cause allergic skin reactions".

If certification according to the DGNB (German Sustainable Building Council) is to be obtained, the target value of 0.05 mg/m³, i.e., half the guideline value, should be adhered to. If the guideline value is exceeded, DGNB certification is not possible.

Where is formaldehyde used?

Formaldehyde is used in countless products and materials. As a result, it also easily finds its way into indoor spaces. Starting with textiles, flooring, furniture as well as in disinfectants or even cosmetics - all these are sources that can increase the concentration of formaldehyde indoors.

Let's take a closer look at a typical living room:


Decoration fabrics

Formaldehyde is often used in decorative textiles such as carpets or curtains to make the fibre more stable; in carpets also often to bond the fibre to the backing fabric.

Wall paint

Formaldehyde is used as a preservative in varnishes and wall paints. Exposure to the pollutant is temporary at best, but then usually at alarming levels.


Finishing" is when certain properties of textiles are changed through the use of chemicals. For example, formaldehyde is often used to make clothing crease-resistant.


Chipboards are pressed, glued wooden boards, often glued with decorative laminates for furniture. The glue may contain formaldehyde, which the furniture releases over a long period of time.

Floor adhesive

Resins are the basis of adhesives: When the solvent evaporates, an adhesive film is formed. In the case of the often-used formaldehyde resin, the pollutant then slowly evaporates.


In carpeting for fibre stabilisation, in laminate or prefabricated parquet for gluing the boards: formaldehyde is often also hidden in the floor covering. Not so with solid wood, rarely with tiles.

Ground sealing

Raw wood parquet or wooden floorboards are often sealed for protection. Be careful when choosing a sealant: it may contain formaldehyde. But there are also products that absorb formaldehyde.


Formaldehyde kills most germs and is therefore often found in disinfectants.

What to look out for to avoid formaldehyde?

Blue Angel eco-label Blue Angel eco-label

One can, however, avoid formaldehyde. There are now various quality seals and labels that make it easier to keep track.

One of these seals is the "Blue Angel". This is an environmental label of the German Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety.

  • The criteria are emissions, ingredients and environmentally friendly disposal.
  • If all categories are assessed positively, the seal is awarded. Products or product groups that are currently labelled with this seal include furniture, electrical appliances, cleaning products, paper, vehicles and various building materials (varnishes, paints, insulating materials, etc.).
  • The testing is carried out by external experts.
  • This seal has been in existence since 1978.


eco-label eco-label

In addition to the Blue Angel, there are other environmental labels. The ISO standard roughly distinguishes between three types of environmental labels.

  • Type I includes the "Blue Angel".
  • Type II includes environment-related supplier declarations. In most cases, there is no independent verification. However, the requirements of DIN EN ISO 14021 must be complied with. For example, certain requirements must be met for protected terms such as "compostable", "recyclable" or "reduced energy consumption". The term "sustainable" is also prohibited in this context, as there are no procedures for measurement or assessment criteria at product level.
  • Type III ecolabels are subject to the requirements of DIN EN ISO 14025 and display additional information relating to environmental and health protection. They are awarded by external bodies. In contrast to the two previous types, the target group is not building owners, but primarily economic actors such as planners or auditors.

Can you neutralise formaldehyde?

If the limit value of formaldehyde is exceeded, the question arises: can formaldehyde be neutralised? The answer is that yes, it can. In industry, especially in the construction sector, workers are in contact with various paints or solvents. Here, the formaldehyde concentration is reduced with certain exhaust systems. Such a system would however be difficult to install in one's own living and working area. Nevertheless, there are many tips and tricks to improve indoor air quality. Here are a number of very effective ways to reduce or remove formaldehyde from a living space:

  • Regular (shock) ventilation works wonders. The air is completely exchanged, and the formaldehyde concentration can be kept low.
Green plants as air purifiers Green plants as air purifiers
  • Green plants are true "pollutant killers". They not only neutralise toxins in homes, but also provide an ideal living and working environment through their oxygen production. Here are the profiles of our favourite natural warriors:
    • Areca palm: the popular palm is a real ‘pick-me-up’ houseplant. In addition to neutralising formaldehyde, it is also effective against xylene and toluene, substances that can trigger fatigue and discomfort.
    • Birch fig: formaldehyde and ammonia don't stand a chance with this green plant.
    • Rubber tree: this houseplant fights formaldehyde like no other. It has an above-average decomposition rate.
    • Real aloe / aloe vera: known as a medicinal plant, aloe vera is an ideal oxygen supplier. As an indoor plant, it also breaks down small traces of formaldehyde in the air.
    • Ivy: not only is it a talented climber that feels at home in partial shade, but ivy is also a good formaldehyde decomposer.
    • Poinsettia: this green plant not only spreads a Christmassy festive mood, but it also breaks down slight traces of formaldehyde in the air.
  • If plants aren’t really your thing, you can now use various ventilation systems or air purifiers. If the concentration of formaldehyde is too high, however, one must be careful that HEPA filters do not catch the molecules of formaldehyde because of their small size. A combination of photocatalysts with activated carbon filters is best. Besides neutralising formaldehyde, such air purifiers can also eliminate allergens, bacteria, pollen or even mould spores.

Building products: what research is being done?

Since the concentration of formaldehyde in some buildings has had harmful effects on health after construction, the materials used are continuously being further developed. The goal is constant improvement and the creation of an optimal indoor climate. In the meantime, there have been good milestones of success, which help both in prevention and in the case of renovation:

Bio-based wall paint Bio-based wall paint
Organic based wall paint

Could a certain type of wall paint reduce levels of formaldehyde in indoor air by more than 70 %? That sounds almost too good to be true. But thanks to the innovative Indoor Air Technology from the company Sigma Fresh Air, this fact has become a reality. A double coat of paint can neutralise up to 70 % of the formaldehyde concentration and does so for years. What’s more, Biofa has another offer at hand: a special biological primer to be applied under the wall paint. The degradation of formaldehyde here takes place through the keratin bond similar to that of sheep wool. An additional advantage of the primer is that it strengthens the substrate. However, due to the small amounts of formaldehyde absorbing substances, the "filtering capacity" decreases rapidly compared to other methods. In return, the paint can be reapplied relatively easily and the "filter performance" is back.

Rigips boards with air purification effect Rigips boards with air purification effect
Rigips boards with air purification effect

In interior finishing, there are also improvements and product developments. Air-purifying boards for walls and ceilings are already on the market. Rigips offers boards with the premium air purification effect known as "Activ Air". Formaldehyde and other volatile organic pollutants are absorbed by the boards and rendered harmless by a special active complex. According to calculations, this effect should last at least 50 years.

Minerals in chipboard and plywood Minerals in chipboard and plywood
Minerals in chipboard and plywood

Adhesives containing formaldehyde are to be expected in about 85 % of all wood-based panels. In 2010, researchers from the Fraunhofer Institutes for Wood Research WKI in Braunschweig and for Silicate Research ISC in Würzburg found out that synthetic Zelolith Y absorbs pollutants. Tests with sample chipboards made of spruce wood showed a reduction in formaldehyde emissions from the boards of around 40 %.

Formaldehyde-free white glue Formaldehyde-free white glue
Formaldehyde-free white glue

Probably the best known wood glue is white glue. This product is a formaldehyde-free and solvent-free dispersion white liquid which becomes transparent when cured. It is used by both amateurs and professionals to join wood or wood materials. White glue is particularly suitable for decorative building panels. For static wood construction elements, the formaldehyde-free alternative is a suitable option – PU glue (PMDI).

How neutralising formaldehyde with sheep wool works

Sheep wool is a naturally occurring and renewable resource. In sustainable construction, more and more use is being made of this resource. And for good reason, also with regard to the neutralisation of formaldehyde within indoor air. But how does it work and is the effect permanent?

Sheep's wool under the magnifying glass Sheep's wool under the magnifying glass

Let’s take a closer look at sheep wool

The protein fibre fabric is a natural fibre. It is breathable, permeable to air and due to its good elasticity, it keeps its shape almost perfectly. Looking at its chemical composition, anhydrous sheep's wool consists of 97 % proteins, which are classified as keratins. The remaining 3 % are formed from structural lipids, mineral salts, nucleic acids and carbohydrates. The elemental composition is characteristic of proteins, but the high sulphur content of 3.5 % stands out. This high content can be attributed to the amino acid cystine. Due to an elevated content of nitrogen and moisture, sheep's wool is difficult to ignite and only burns above a temperature of 560 degrees Celsius.

Sheep's wool is a composite structure whose fibres consist of two different cell types. The epidermis, the so-called cutica, consists of fine scales that are arranged around fibre-like ‘roof’ tiles. This cuticle has an amazing degree of cross-linking, which makes it very robust against chemical substances and gives it mechanical toughness. Around this scaly cover is the epicuticle. Inside the fibres are the cortex cells, which form the main component of the fibres with 90 %. These are responsible for the mechanical properties of wool.

Sheep wool and formaldehyde

The reactivity of wool with formaldehyde has been investigated in several studies since the 20th century. In the beginning, formaldehyde was used to improve the properties of wool. For example, it was used as a wool preservative in dyeing until the 1970s. In the meantime, sheep wool is increasingly used in construction. Through its proteins, it can chemically restrict pollutants from air, thus acting as a kind of physical and chemical filter. This capacity is particularly noticeable in the case of formaldehyde. Laboratory tests showed that sheep's wool absorbed 98 % of formaldehyde from indoor room air. A release could not be substantiated. Accordingly, sheep's wool irreversibly binds formaldehyde.

Sheep's wool and formaldehyde Sheep's wool and formaldehyde

Installation of sheep wool

Sheep wool can be installed in different ways. The most effective is to cover the entire surface of the affected walls or ceilings with tightly needled fleece. Likewise, the wool can be applied to a "suspended ceiling". A small additional benefit of this variant is that sound insulation is improved.

Sheep wool can also bind formaldehyde on the inside of a wall. This is the case, for example, with walls insulated with ISOLENA sheep's wool products and covered with OSB boards. The type of wool, whether felted, needled or loose, is irrelevant and has no effect on its pollutant filtering capacity.

Measured values

The DWI (German Wool Institute) has conducted studies on the topic of "Absorption and Binding of Indoor Pollutants by Wool Using Formaldehyde as an Example". Rooms contaminated with formaldehyde were simulated in test chambers in order to simulate the conditions for remediation measures using sheep wool. All tests showed the same result: after only two hours, more than 80 % of the formaldehyde load was absorbed by the wool. After 24 hours, the value was 96 %. The asymptotic curve of the tests always pointed towards zero.

Furthermore, several practical tests in residential and municipal buildings, where removal of the formaldehyde sources was usually practically impossible for structural reasons, resulted in a reduction of the formaldehyde concentration from approx. 0.06 to 0.2 ppm to below 0.05 ppm, which is less than half of the BgVV guideline value.

Formaldehyde measurement in the laboratory Formaldehyde measurement in the laboratory

Examples of successful formaldehyde remediations

Even with seemingly well-planned building projects, it can happen that one forgets to keep an eye on formaldehyde concentrations. Due to the large number of components used in interior construction, the concentration can quickly exceed the limit value and cause health problems. With the help of targeted renovation measures, however, this can also be brought under control, as the following examples show:

Renovation of the new building of the Oberstufenzentrum Ost in Felben-Wellhausen Renovation of the new building of the Oberstufenzentrum Ost in Felben-Wellhausen

New construction of the East Oberstufenzentrum in Felben-Wellhausen

In Felben-Wellhausen, the high school was able to look forward to the new building in which they would be taught in the future in the summer of 2004. But after only a short time, students and teachers complained about health problems. Measurements showed a far too high concentration of formaldehyde in the interior rooms. The remediation of this issue was carried out with the help of sheep's wool. This was effective as levels reduced relatively quickly, and eventually the problem ceased to occur all together.

More about the formaldehyde remediation in the school building →

Renovation project for a kindergarten in Langenfeld near Cologne

An excessively high formaldehyde concentration was detected in a kindergarten in Langenfeld. This was due to wood-based materials: chipboard on walls and ceilings. Several remediation attempts failed, and a demolition of the building was considered. On a trial basis, one room was renovated with sheep's wool. A few days later, the legal guideline value of the formaldehyde concentration of 0.1 ppm was reached and levels of formaldehyde had reduced to a mere 0.04 ppm. The entire kindergarten was then to be renovated.

(Source: Robert Sweredjuk, Gabriele Wortmann, Gerd Zwiener, Fritz Doppelmayer: "Sheep wool as a reactive sorbent for indoor air pollutants")

Renovation project for a kindergarten in Langenfeld near Cologne Renovation project for a kindergarten in Langenfeld near Cologne


Building a house is all about one’s inner values. If you look out for possible "polluters" before you start building, you can save yourself expensive renovations later on. Often, the price differences are somewhat off-putting. But if you look at the least expensive options more closely, they are not always as attractive as you might initially think. A direct conversation with the builder about possible ecological alternatives therefore could never do any harm.

With sheep wool in particular, one can already note the advantageous differences during construction - no waste, pure nature, quick and easy processing - the best starting point for an indoor climate that makes you feel good.