4. The return of explosive gas out of the gas engine into the gas pipe by failure to ignite or other accident, must be made impossible.
5. The apparatus through which the generator is charged must possess a tightly fitting double valve to prevent escape of gas into the room during charging.
6. The pipes for conducting away the unpleasantly smelling bituminous constituents in the water mixed with sulphuretted hydrogen from the scrubbers must not communicate with the workroom.
7. Precautions must be taken to minimise the danger during the cleaning of the generator (removal of ashes and slag).
8. All stop-cocks and valves are to be so arranged that their position at any time (open or shut) is clearly visible from outside.
9. Purifiers with a capacity greater than two cubic meters must be provided with appliances which make possible thorough removal of the gas before they are opened.
10. The gas washing and cleaning apparatus and pipes are to be fitted with gauges indicating the pressure existing in them at any moment.
11. When a suction gas plant is first installed and also at times when there is no gas in the pipes and plant between the generator and the engine, gas must be blown in until all air is expelled before the engine is set going.
12. During the cleaning of apparatus and pipes which, when in action, contain gas, the rooms must be thoroughly ventilated.
13. Rooms in which suction gas plant is installed must be of such a height that all the plant and its connections can be easily reached for cleaning, &c., and be capable of such free ventilation as to render impossible an accumulation of gas.