Testing for a gas leak - the Georgian way

Today in the office there was a distinct whiff of gas from the gas heater beside my desk, especially with the windows closed. So the lads decided to investigate. Out came the matches... which were then run along the gas pipe to identify exactly the source of the leak. Nothing found (thankfully!). There was another gas pipe along the ceiling but the guys were to short to reach it with a match; so they lit an A4 sized piece of paper and ran it along the pipe. As one does.