Types of asbestos

Both asbestos cement and asbestos insulation board (AIB) contain asbestos used in sheet or board form.

Because of the relatively higher potential risks to health arising, working with asbestos insulating board is subject to different and more stringent controls than working with asbestos cement.

As the two materials are very similar in physical appearance, depending upon the circumstances, it is necessary to distinguish between them.

The distinction is one of density, the general rule being that the greater the proportion of cementitious matrix to asbestos, the greater the density. Conversely, the more friable the material, the greater the asbestos content.

The Approved Code of Practice that accompanied CAR 2012 defines asbestos cement as 'a material which is predominantly a mixture of cement and asbestos and which in a dry state absorbs less than 30% water by weight'. The guidance in the document includes a comprehensive description of the testing procedure.

Asbestos insulating board is defined as a flat sheet, tile or building board consisting of a mixture of asbestos and other material except asbestos cement or any article of bitumen, plastic, resin or rubber which contains asbestos, and the thermal or acoustic properties of which are incidental to its main purpose.

It is relatively easy to identify asbestos cement when it is used in preformed components such as corrugated sheeting, tanks or toilet cisterns, but when it is used in flat board form the only sure way of distinguishing the material from AIB is by laboratory analysis.

Where there is doubt, err on the side of caution, assume that the material is AIB and take precautions accordingly.