1.   Solids can release gases back into the atmosphere when heated and pressed by volcanic activity.

2.   The device contains a carbon dioxide cylinder which released gas into a coiled chamber.

3.   Modern equipment is extremely complex and some systems have up to seven separate cleaning stages before any gas is released into the atmosphere.

4.   An automatic fire-extinguishing system that releases halon gas to smother flames had not worked, apparently because a light-heat sensor had been covered.

5.   As with two other mysterious poison gas incidents in Yokohama, there was no sign of a container or other method of releasing the gas.

6.   A built-in safety mechanism designed to release the gas meant the balloon would not travel too far.

7.   A fumigator attempting to close the valve himself broke it instead, releasing gas that set the house on fire.

8.   Combustion devices, like stoves, furnaces, heaters and fireplaces, can release dangerous gases into the home.

9.   Heat causes materials, like wood, candle wax or fabrics, to release gases, which then fuel the fire in the presence of oxygen.