Article 4 Descriptions of radioactive material to which exemption relates
Article 3 applies to radioactive material falling within either of the following descriptions, that is to say—
(a)
a smoke detector which is radioactive material solely because it contains americium 241 in one or more closed sources in which, or in all of which taken together, the sum total of kilobecquerels does not exceed 40; or
(b)
a smoke detector, not being a smoke detector falling within paragraph (a) of this Article, which is affixed or attached to the premises and is radioactive material solely because it contains radionuclides in one or more closed sources in which, or in all of which taken together, the sum total of megabecquerels of all the radionuclides (including those which are decay products of others present) does not exceed 4.