21.   The government oil monopoly Pemex has been producing gas from three wells on his land for two decades.

22.   The gas is produced by burning fossil fuels.

23.   The second fermentation produces carbon dioxide gas, creating the characteristic bubbles.

24.   The wells produced sour gas, a gas laced with hydrogen sulfide, a neurotoxin that can be as deadly as cyanide.

25.   They suspect that the gas is produced when the converter is warming up, and believe the converters could be redesigned to reach optimum temperature faster.

26.   This gas is produced by the incomplete combustion of fuel such as gasoline, coal, oil, natural gas, propane and kerosene.

27.   Those gases are produced by burning fossil fuels such as coal, oil and natural gas.

28.   Under very low light in an overheated room, chrysanthemums can produce ethylene gas.

29.   Vehicles, industry and agriculture produce the gas when they burn fossil fuels.

30.   Use extreme caution when handling a battery, since it can produce explosive gases.