Fire requires three basic elements – heat, fuel, and oxygen. If any one of these elements is missing, fire cannot occur or be sustained. So in theory, anything that does not contain those three components cannot burn.
Things That Cannot Burn
Here are some examples of things that cannot burn:
- Water – Water contains no fuel source and smothers fire by cutting off oxygen supply.
- Nitrogen gas – Nitrogen is non-flammable and makes up 78% of the air we breathe.
- Concrete/stone – These materials are incombustible as they contain no fuel source.
- Fire extinguishers – Fire extinguishers work by displacing oxygen, removing heat, or coating fuels with flame-retardant chemicals.
However, while those materials cannot burn directly, with enough heat applied almost anything can be incinerated or melted. But under normal conditions, the things listed above will not ignite and burn.
What Makes Something Flammable?
For something to burn, it must contain elements that can act as fuel. The most common fuels that can readily burn are:
- Wood/paper – Contain cellulose that ignites easily.
- Fabrics/fibers – Made of materials like cotton, wool, nylon that can burn.
- Coal/fossil fuels – Hydrocarbons like petroleum and gas ignite easily.
- Plastics – Made of hydrocarbon polymers that release flammable vapors.
- Chemicals – Flammable substances like alcohol, acetone, or gunpowder.
The chemical composition and structure of a material determines how easily it ignites and burns. Materials made of elements like carbon, hydrogen, and oxygen typically make good fuels.
Making Things Fireproof
While some things are naturally non-flammable, other materials can be treated to become fireproof or fire-resistant:
- Fireproof coatings – Fire retardant paints/sprays that form a protective barrier limiting oxygen.
- Mineral insulation – Materials like fiberglass insulate and don’t burn easily.
- Fire-resistant fabrics – Fabrics treated with chemicals that inhibit burning.
- Flame-retardant additives – Chemicals added to plastics or foams to slow ignition.
These treatments work by limiting oxygen supply, reducing capability of materials to ignite, slowing down burning, and decreasing smoke production.
Extreme Heat and Fire
While some things are normally non-flammable, when exposed to extreme heat from an intensely hot fire or heat source, even stones, metals, and glass can be made to burn:
- Most rocks and soil contain trace amounts of flammable minerals that can burn when intensely heated.
- Metals like aluminum, magnesium, titanium, and iron can oxidize and burn in hot-enough fire.
- Glass is made of sand and contains enough oxygen to theoretically ignite if heated to over 4000°F.
So even some of the most fire-resistant materials will eventually burn or melt if the fire is hot enough. The resulting molten materials may spread the fire further through flammable liquids.
Water and Fire
One of the most effective ways to extinguish fire is with water. But even water will eventually boil and evaporate with enough heat applied. However, very large bodies of water like oceans, lakes, or pools will not burn or boil, because:
- The enormous heat capacity of water makes it extremely difficult to heat up.
- The constant cycling of cooler water prevents sustained heating at the surface.
- Water cuts off oxygen supply and smothers the fire before heat can build up.
So massive volumes of water essentially act as infinite heat sinks able to dissipate heat faster than fire can build it up. But small or stagnant bodies of water can potentially boil away or evaporate from intense fire.
Vacuum Environments
For combustion and fire, oxygen is absolutely required. In the vacuum of space or other oxygen-free environments, there is no risk of fire since no oxygen exists. Some examples include:
- Outer space
- Underwater habitats or submarines
- Pressurized habitats filled with inert gases
- Industrial environments using inert gases like argon or nitrogen
So fire and combustion cannot occur in a true vacuum or atmosphere devoid of oxygen. But any introduction of an ignition source and oxygen will create fire risk once again.
Conclusion
In summary, while many materials are naturally fireproof due to their composition, almost anything will burn under the right conditions of having adequate heat, fuel, and oxygen present. However, some exceptions like massive bodies of water, true vacuums, or atmospheres lacking oxygen make fire impossible until air is introduced.
Understanding what makes materials flammable versus fireproof is key to fire prevention and safety. Taking steps to use fire-resistant materials and be aware of potential ignition hazards is important in minimizing fire danger to protect lives and property.