Section 60(1)(a) in The U.P. Factories Rules, 1950
(a)The operation of repairing a water sealed gas-holder by the electric welding process, subject to the conditions that:(i)The gas-holder shall contain only the following gases, separately or mixed at a pressure greater than atmospheric pressure, namely, town gas coke, oven gas, producer gas, blast furnace gas, or gases other than air, used in their manufacture :