While it is difficult and costly to construct a completely fireproof structure, it is reasonable to construct buildings that are significantly fire resistant. Firefighters will readily agree that no two fires are exactly the same even in seemingly identical structures. But there are similarities in certain aspects of how fires start, spread, and extinguish in buildings and structures. Therefore techniques used for fire resistant construction attempt to take advantage of these similar processes.
Fire typically requires four elements: fuel, oxygen, heat, and a chemical chain reaction. To start a fire there needs to be a source of heat in the presence of oxygen (or an oxidizer of some kind) and a bit of fuel. These must combine to begin the chemical chain reaction needed to generate additional heat, which consumes more fuel and oxygen, generating more heat, and so on. Removing any one or more of these elements will prevent and/or suppress a fire. Creating fire resistant structures then can be as simple as using non-combustible construction materials such as metals, concrete, masonry, clay, sand, glass, cork, ceramics, etc. However, as developed as these materials have become in terms of aesthetics, combustible materials are still typically desirable for interior and exterior design, finish work, furniture, floor coverings, and so on.
An additional prevention step is to exclude oxygen, but for obvious reasons this technique is limited to applying gas impermeable coatings to a limited selection of combustible materials. In doing so care must be taken to avoid generation of poisonous gases and fumes if combustion does manage to start, as they may be more hazardous than the fire itself.
Which leaves the final prevention step of eliminating sources of excess heat, sparks, and exposed flame. Electronic ignition used in gas appliances, spark arrestors, appropriate attention to electrical wiring codes and power usage, and less reliance on flame based heating appliances like fireplaces and wood stoves have significantly reduced the related incidence of fires started by these sources.
However much care is taken to prevent structure fires from starting, they will almost certainly continue to ignite due to accidents, negligence, arson, carelessness, and equipment failures. The next best fire defense then is to prevent it from spreading once started. Several construction techniques are used to achieve this goal. Passive measures such as spray applied fire proofing coatings can be used in inaccessible, non-finished areas. Fire stops are required by most building codes and consist of blocks, putty, sleeves, caulking, sealants, and/or intumescent materials. They function by preventing a fire from spreading through joints, penetrations, and framing gaps between and through walls, floors, and ceilings. Controlled openings for access and ventilation along with blocking vacant vertical shafts (such as chutes, elevator runs, stairwells, etc.) prevent them from acting as chimneys during a fire. This can effectively oxygen-starve combustion and help with suppression. Used in conjunction with rated fire walls, ceilings, floors, and doors these techniques effectively compartmentalize a fire and slows or prevents its spread.
Built-in active measures are also used to suppress fires in progress. These include automated sprinkler systems and chemical extinguishers, automated door closers, and alarm systems. While typically more expensive to incorporate than passive measures, active measures have been shown to be extremely effective in slowing and even suppressing fires that would have otherwise become uncontrollable. And with a structure fire occurring almost every minute in the United States alone, it is clear that all available prevention and suppression measures will continue to be needed in building construction for many years to come.