Where the hazardous gas, vapour, dust or fumes are of an explosive or flammable nature, an employer or user of machinery must further take steps to ensure that such a confined space is entered only if -
- the concentration of the gas, vapour, dust or fumes does not exceed 25 per cent of the lower explosive limit of the gas, = vapour, dust or fumes concerned where the work to be performed is of such a nature that it does not create a source of ignition; or
- such concentration does not exceed 10 per cent of the lower explosive limit of the gas, vapour, dust or fumes where other work is performed.