Sch 1 para 9 Enclosed structures and prevention of leaks
(1) Equipment which may release flammable gases or dusts must, wherever possible, employ enclosed structures only. (2) If equipment contains openings or non-tight joints, these must, as far as possible, be designed in such a way that releases of gases or dusts cannot give rise to explosive atmospheres outside the equipment. (3) Points where materials are introduced or drawn off must, as far as possible, be designed and equipped so as to limit releases of flammable materials during filling or draining.