2. Where it is not practicable for an employer to substitute for chrysotile a substance which, under the conditions of its use, does not create a risk to the health of his employees or creates a lesser risk than that created by chrysotile, regulations 26(3), 27(1), 28(1) and 29(1) shall not apply to—
(a)Diaphragms for use in electrolytic cells in existing electrolysis plants for chlor-alkali manufacture;
(b)chrysotile, or products to which chrysotile has intentionally been added, required solely for the manufacture of the products described in sub-paragraph (a).