We got calls from customers that they confuse about asbestos with RCF (Refractory Ceramic Fiber). Actually the two fibers are totally different from many characteristics. Asbestos is not a refractory fiber! It was used in a wide range of construction materials in the past. The toxicity of asbestos has been proven by many human and experimental studies and it was banned in China for years. The toxicity of RCF, however, is suspected on the basis of confusing and conflicting experimental studies. RCF has no demonstrated human toxicity per the EU guidance.
The following information was cited from <Recognition and control of exposures to refractory ceramic fibers (RCF> published by ECFIA, which is also available online for reference.
As a matter of precaution, and in accordance with the recent classification of RCF, exposures must be controlled and kept as low as possible. Control strategies and methods developed for asbestos should not be automatically transposed to RCF without accounting for the fundamental differences between the two fibre types and the two markets. This guide outlines a series of precautions tailored to the use of RCF products. These are based on the more general requirements for the protection of workers from carcinogens at work.
An important property determining dust release and control is the size distribution of fibres. Asbestos fibres are very fine. For example, the diameter of chrysotile fibrils is about 0.03 µm. Because of this small diameter, asbestos products can generate fibrous dust that remains airborne for long periods and, if inhaled, has a very high probability of penetrating deep into the lungs. Almost all airborne asbestos fibres are in the respirable range (fibres with a diameter less than 3 microns).RCF products also contain some fibres in the respirable range, but overall RCF fibres are much coarser than asbestos fibres, with diameters distributed around 3 microns. Consequently, RCF products have lower potential for dust release. Airborne RCF fibres tend to settle rapidly and have a lower probability of penetrating into the alveolar region of the lung. Length and diameter analysis by electron microscopy
shows that the distributions of RCF and chrysotile airborne fibres are quite distinct, with very little overlap.
Phase-contrast optical microscopy can detect the vast majority of RCF airborne fibres, whereas transmission electron microscopy is needed for asbestos. For RCF dust, an optical microscopy count will detect almost all fibres present; However, it may report only a few percent for
