1. In regulation 2(1) for the definitions of “action level” and “control limit” substitute the following definitions—
““action level” means one of the following cumulative exposures to asbestos over a continuous 12-week period when measured or calculated by a method approved by the Health and Safety Commission, namely—
(a)where the exposure is solely to chrysotile, 96 fibre-hours per millilitre of air; or
(b)where exposure is to any other form of asbestos either alone or in mixtures including mixtures of chrysotile with any other form of asbestos, 48 fibre-hours per millilitre of air; or
(c)where both types of exposure occur separately during the 12-week period concerned, a proportionate number of fibre-hours per millilitre of air;”.
““control limit” means one of the following concentrations of asbestos in the atmosphere when measured or calculated by a method approved by the Health and Safety Commission, namely—
(a)for chrysotile—
(i)0.5 fibres per millilitre of air averaged over any continuous period of 4 hours,
(ii)1.5 fibres per millilitre of air averaged over any continuous period of 10 minutes;’
(b)for any other form of asbestos either alone or in mixtures including mixtures of chrysotile with any other form of asbestos—
(i)0.2 fibres per millilitre of air averaged over any continuous period of 4 hours,
(ii)0.6 fibres per millilitre of air averaged over any continuous period of 10 minutes;”.