Mostly found in or on heating systems such as around boilers or calorifiers and around pipework.
This type of asbestos has many different appearances but is mostly a fibrous material which flakes and powders easily. When applied to pipes it is often covered in a protective coating (or painted) which can be any colour, and may make it more difficult to identify.
This is one of the most dangerous materials containing asbestos. You are more at risk from breathing in asbestos fibres because disturbance of the lagging or insulation releases fibres very easily into the air that you breathe.
Do not attempt to work on this material under any circumstances unless you are a HSE-licensed contractor.