Formaldehyde is a volatile small molecule that is commonly contained in resins and adhesives. In textiles, formaldehyde is often contained in protective clothing or non-iron shirts, amongst others. Formaldehyde is classified as carcinogenic to the respiratory tract and the substance is limited to 75 mg/kg for clothing in the EU.

Formaldehyde can be freely present in clothing in its molecular form and enter the environment via the air or by washing. Bound formaldehyde can be released from its matrix, i.e. a textile product, and the release can be measured. The value for released formaldehyde is usually higher than that for free formaldehyde. Formaldehyde also occurs in wood, especially in pressboard or otherwise processed wood.

The testing for free formaldehyde including the previous extraction is standardised according to DIN EN ISO 14184-1 and CTL® GmbH is accredited for this procedure. After cutting the test piece into a defined sample size, the formaldehyde is extracted from it with water. The extract is mixed with the so-called Nash reagent. This reacts with formaldehyde to a yellow colour. The formaldehyde concentration in the extract is measured photometrically and extrapolated to the previously determined weight of the test piece in mg formaldehyde per kg textile (mg/kg).

The procedure can be applied to any type of fibre and any type of textile. Fibers without special equipment rarely show high levels of formaldehyde. According to the standard, the limit of quantification is 16 mg/kg, at CTL® GmbH we can even safely prove a content of 5 mg/kg.