There is often much contention between firefighters about who is the most important, the truckies or the pipemen? Although I like spraying water as much as the next guy, I've always been a truckie at heart. That being said, the engine company is one of the most vital parts of the strategy, because you need to spray water to put out the fire. True that it will eventually burn itself out, but one of the main fire service tenants is to conserve property, and letting it burn doesn't match up with that priority.
The idea behind fire attack has always been to put water on the fire, and that idea has changed much over the years. The fire service used to be dominated by straight tipped nozzles that sprayed out a solid stream of water. In the 1950's Lloyd Laymen, former Chief of the US Coast Guard Fire Training Center, devised a new form of fire attack using a fog nozzle. This was an idea imported from the naval services, since they used fog nozzles to control shipboard fires quickly. The new concept was adopted by the mainstream fire service quickly, but there was a catch...
Laymen never actually intended for the fog nozzle to be used in an interior attack mode. That's right, not go to an interior attack. This misunderstanding was quickly applied and often with disastrous results. It was continued up until the 1980's, when smooth nozzles started to become common place again, but even today they are far less common than prior to the advent of the fog nozzle. Smooth nozzles require a lot more skill to use and are far easier to handle because of low nozzle reaction. Remember Newton's First Law? Every action has an equal and opposite reaction? The more pressure you pump to a nozzle the higher the reaction force at the point of discharge will be, so if you are pumping 100 psi to a nozzle, you will be getting an equal amount of reaction force at the nozzle.
So the attack REALLY starts before you even make it to the fire. You should familiarize yourself with what you have available, and what your hose lines can do. This is only achievable through study and training. Waiting until you are at the fire to become familiar with your gear is not the right moment. Often individual shifts or in the case of volunteer services, individuals themselves, will prefer a different set up based on their chief or company officer's beliefs. If you are not part of that shift, you need to pay attention what nozzle or hand tools have been misplaced or moved and either move them back or remember where they are.
Often hose will be removed at a fire and may not be replaced. You should keep note of how many sections of hose you have pre-connected or in the beds so you will not "lay out short" and need to stretch additional hose to make up the difference.
As a company officer, the size of the initial line makes a difference in how quickly you get a stop on a fire. The heat release curve states that the maximum heat release is achieved during a free burning period just after flashover, but is not maintained for very long, and eventually burns down into a smoldering state. With this in mind, remember that using a small handline (1.75 inch, usually) while the fire is post-flashover and into a free burning state will not do much. The application of water is directly proportional to the heat release curve, meaning that if you do not apply enough water to combat the heat release of burning materials, you will be getting nowhere on the fire, and it may even advance on you. Lines in excess of 2 inches are preferred. They are not easy to manage when charged and require extra muscle to position, but you will not be fighting fire for very long.
This is where the discussion on nozzles comes in. If you are pumping 150 psi to a fog nozzle on the end of a large handline there will be a HUGE difference in reaction force opposed to 50 or 75 psi, with better flow from the smooth nozzle because there is less in the nozzle itself to impede flow.
Something that is very rarely considered is the air flow into the fire area, which can rapidly change the conditions. A fog nozzle even at a 30 degree fog pattern will entrain over 1000 ft3 of air into the air. This when combined with water hitting superheated materials and converting to steam will produce a steam flow along the path of least resistance (which is usually the path the hose team traveled) and push superheated gas back onto the hose team. This is disrupting the thermal layer, and without ventilation to create that path of least resistance.
Once you have worked your line into position and it's charged, you can now spray water. There is no hard and fast rule, but there are some things to keep in mind. If you spray water directly on what's burning, you will scatter it all over. I prefer an indirect spray pattern regardless of what nozzle you are using. The circular pattern is the easiest to remember and easiest to do, and doesn't involve sharp movements of the nozzle. You should spray water so that it hits both walls, the ceiling, and the floor.
Why the floor? This allows you to use the water stream to sweep the floor of debris that falls in your path as well as cooling the area where you will soon be crawling or walking.
Once you have extinguished the fire, you will be moving immediately into the overhaul phase, but that's another article...