Every gas has a certain grade of combustibility. The combustibility determines how the gas will react with open flames and how efficient it is as a fuel in a Gas Furnace or Gas Lantern.
| Name | Fuel efficiency | Open flame interaction |
|---|---|---|
| None | 0 | None |
| Controllable | 1 | None |
| Flammable | 2 | Becomes Ignited Gas and spreads |
| Highly flammable | 3 | Becomes Ignited Gas and spreads quickly |
| Explosive | 4 | Creates an explosion with power depending on gas volume |
| Highly explosive | 5 | Creates a powerful explosion with power depending on gas volume |
The fuel efficiency determines for how long a volume of gas can last as a fuel, or if it even counts as a fuel at all. For instance, a highly explosive gas can keep a furnace running for 5 times as long as a controllable gas, while a non-combustible gas will not work as fuel.