Reply To: Moss from AC roofing

Home Forums Members Only Forums Technical Discussion Moss from AC roofing Reply To: Moss from AC roofing


    In my opinion, and understanding, HSL/2007/11 was a paper produced following arguments that chrysotile could be chemically altered during the process of creating AC and that AC may not need to be considered as ‘asbestos’ as a result. It is not my recollection that it was the source of  ‘a load of exposure stats’ on AC but that (and this post) is just my opinion.

    The samples referred to in Annex 1 of that paper are taken from the same list of samples used in RIA176 (that has other products as well) and in other CDs as well.

    The methods for removal and working on asbestos have improved considerably since the period that these samples were taken, being 1985 to 2000.

    The use of the Control Limit to determine whether work is licensable, or not, is after the control measures have been implemented, i.e. it is the potential exposure to workers during the planned work following the PoW provided by the employer – and the PoW ought to be written by a competent person.

    AC will have deteriorated to varying degrees since those samples were obtained over 2o years ago. The rate of deterioration was estimated at around 0.024 mm/year (uncoated AC (Spurny, K.R. 1989)) and it could be therefore be argued that if replicated now, in 2024, that the exposures may be higher as a result of that deterioration.

    Irrespective of anything else methods have improved considerably and a better and more informed workforce with adequate training and control mean that work on AC does not generally exceed the current Control Limit or STEL. This has certainly been borne out by my personal experience over the last 35+ years in any event.