CMFs are industrially manufactured artificial mineral fibres. A distinction is made between four groups Glass wool (white or yellow long fibres), Rock wool (darker, greenish-yellow fibres), Slag wool (dark, brownish fibres; not very common) and Ceramic fibres (white; high temperature wool).
CMFs were and are primarily used for heat and sound insulation (e.g. in roofs, ceilings and walls, in ventilation and heating systems), sometimes also as a replacement for products containing asbestos. KMF produced before 1996 is classified as "Old mineral wool" are labelled. These can release respirable fibres with low biodegradability and are therefore classified as carcinogenic. Following a transitional phase, only biodegradable mineral fibres with the RAL quality mark may be placed on the market since 2000.
