PURPOSE: The titled fuel gas little suffering from danger of explosion and quickly detectable for leakage, which is obtd. by mixing a mixed gas consisting of a specified volume ratio of methane or natural gas and hydrogen with an org. sulfur compd., e.g., thiophene, as an odorant.

CONSTITUTION: About 1W20vol% methane or natural gas is mixed with about 99W80vol% hydrogen. Then the obtd. mixed gas is mixed with at least about 0.1vol% org. sulfur compd. such as ethyl mercaptan, thiophene or isopropyl mercaptan as an odorant, to prepare a fuel gas for heating in fusing and welding. The obtd. fuel gas is highly safe because of a narrowed explosion range when mixed with air and its flame is easily controllable because the flame forms a very distinct white cone. Further, leakage thereof is quickly detected by the smell of the odorant.