5. An employer shall not undertake work in demolition, maintenance, or any other work which exposes or is liable to expose his employees to asbestos in respect of any premises unless either—
(a)he has carried out a suitable and sufficient assessment as to whether asbestos, what type of asbestos, contained in what material and in what condition is present or is liable to be present in those premises; or
(b)if there is doubt as to whether asbestos is present in those premises he—
(i)assumes that asbestos is present, and that it is not chrysotile alone, and
(ii)observes the applicable provisions of these Regulations.