From thenakedscientists.com: A tube is filled with nitrous oxide gas (N2O) and this is mixed with carbon disulphide (CS2). The tube is then put in a safety screen and ignited, with impressive results. The reaction between nitrous oxide gas (N2O) and carbon disulphide (CS2) releases a large amount of energy, as the CS2 reacts with the oxygen in the nitrous oxide to form carbon dioxide (CO2), sulphur dioxide (SO2)and some pure sulphur which is left on the tube at the end.

http://www.thenakedscientists.com/HTML/content/kitchenscience/garage-science/exp/the-barking-dog-experiment/