Asbestos pipe lagging, also known as thermal insulation contains up to 90% asbestos. Making it one of the most dangerous products. The thermal insulation contains crocidolite (blue asbestos). However, it can also contain both amosite (brown asbestos) and chrysotile (white asbestos). Furthermore, the plaster based material mixed with asbestos fibre was extensively used from 1910 through to the late 1970s. As well as being used around hot water pipes, the asbestos lagging made its way into many other asbestos products.
Given that the lagging is extremely friable, handling it is very dangerous as it releases a high amount of asbestos fibres. Encapsulating the thermal insulation should be the very minimum. Although in most cases the safest option is to remove the asbestos lagging.