Standards for industrial flameproof lighting

The principle of containing electrical apparatus within an enclosure of sufficient strength to withstand an internal explosion without igniting an explosive mixture outside the enclosure has been used for many years. BS 229, 'Flameproof enclosure of electrical apparatus', was first published in 1926, and, with four revisions and numerous amendments, served British industry so well that it was adopted by countries throughout the world. What has changed since then?