Robert Temple asserts that the 4th century BC (Warring
States Period) is a conservative estimate for the time in which the
Chinese began using natural gas as fuel and light. He states that
systematic borehole drilling for brine extraction by the 1st century BC
(Han Dynasty) led to the discovery of many "fire wells" in Sichuan which
yielded natural gas. As
recorded in the 2nd century AD, this led to a
systematic search for natural gas. Both brine and natural gas were piped
through bamboo tubes; from small boreholes the gas could be piped
directly to burners where the brine was emptied into cast iron
evaporation pans for boiling and producing salt, but the pungent gas
piped from depths of some 2,000 ft had to be first mixed with air lest
an explosion occur. To remedy this, the Chinese piped the gas first into
a large wooden, cone-shaped chamber placed 3 m (10 ft) below ground
level where another pipe could convey air, thus turning the chamber into
a large carburetor. To avoid fires from a sudden surplus of gas, an
additional "sky thrusting pipe" was used as an exhaust system.
