As discussed in earlier posts, wool is made up of about 18 amino acids leading to its complex molecular and chemical structure. The high reactivity of amino acid chains lends wool its incredible ability to bind itself to toxic air pollutants emitted by Volatile Organic Compunds (VOC).

The most hazardous indoor pollutants are sulphur dioxide (SO2), formaldehyde (HCHO) and Nitrogen dioxide (NO2). The sulphur dioxide and nitrogen dioxide are by products of fuel burning and are commonly caused by fireplaces, home appliances and vehicle exhaust.”

How Wool Combats Nitrogen dioxide (NO2)

A wool carpet in the house can significantly reduce the nitrogen dioxide levels compared to nylon carpets. In a test, both wool and nylon carpets initially absorbed nitrogen dioxide rapidly but wool absorbed it better at different concentrations. But the real problem was noticed on heating wherein the nylon carpet re-emitted twice the volume of absorbed nitrogen dioxide as the woolen carpet.

Also, wool carpet yarn with its superior sorption (better absorption) lowered the volume of nitrogen dioxide by 12 times compared to the nylon carpet yarn. A graphical representation of nitrogen dioxide absorption by wool and nylon carpet yarn is presented below:

How Wool Combats Sulphur DiOxide (SO2)

Tests done comparing the sorption rates of sulphur dioxide of wool, rayon, nylon and viscose fibers showed that rayon and nylon absorbed SO2 rapidly and reached saturation point in 90 minutes. Wool absorbed SO2 steadily in lower amounts over a longer peiod of time.

As discussed above, the unique amino acid chains in wool is responisble for this prolonged absorption of SO2. This is an irreversible chemical reaction with wool releasing less than 1% of the sorbed sulphur dioxide over a 2 hour period.

How Wool Absorbs Formaldehyde (HCHO)

Many homes use resin based wood products like chipboard floors which are active emitters of formaldehyde. These emissions increase with temperature and humidity and the resin hydrolyses releasing the formaldeyde.

Wool with its unique protein structure containing amin acid groups absorbs formaldehyde aggressively in an irreversible chemical reaction without any re-emission. Thus wool effectively and permanently removes formaldehyde from the air inside a home. If the temperature and humidity increases, the increased emission of formaldelyde is effectively repelled by an even higher rate of absorption by wool.

Research shows that wool absorbs formaldehyde effectively at high and low concentrations. Use of wool for indoor furnishings like carpet and wall coverings in buildings affected by formaldehyde has brought down HCHO levels to less than 0.05 parts per million (ppm).