A blaze on the 29th floor of a Chicago high-rise late Monday night injured 37 people. To squelch the fire, firefighters set up their hoses on 26th-floor rooftops and sprayed upward. How high can a fire hose shoot vertically?
Between 75 feet and 100 feet straight up, depending on water pressure. In practice, though, firefighters on the ground rarely attempt to reach higher than 40 feet with hoses. Since water pushes smoke and heat back into the building, attacking a high-rise blaze from the outside can actually be counterproductive. That’s especially true if there’s a chance people may still be trapped inside.
Firefighters can also use truck-borne ladders to reach high places, but scaling a ladder with a heavy hose is often difficult. The general rule of thumb is that ladder-and-hose setups are only effective up to about the 10th floor; after that, it’s imperative that the blaze either be fought from an adjoining structure, such as the Chicago building’s roof wings, or from the inside.
The most common approach in high-rises, then, is to use a building’s standpipe system. This consists of an interior vertical pipe that runs from the ground to the roof, allowing firefighters to connect hoses on any floor. The water usually comes from either a fire truck or a street-level hydrant; firefighters connect a hose from the water source to a standpipe outlet, and it’s then pumped upward to the blaze’s location.
Elevation decreases water pressure, so a tremendous amount of force is needed at ground level to allow for a powerful flow at the point of attack. To fight a fire on the ground, a fire hose needs about 150 pounds per square inch of water pressure. To get water to the 30th floor of a building, the pressure needs to be about 300 PSI to offset the effects of elevation. For comparison’s sake, the standard water pressure in an American home is between 50 PSI and 75 PSI.
Standpipes are helpful in fighting high-rise fires, but nothing is as effective as a sprinkler system—which the 29th floor of the Chicago building lacked. Since the National Fire Protection Association started keeping statistics in the 1920s, there has never been multiple losses of life in a building with a full (and fully functioning) sprinkler system. (The World Trade Center disaster is not included in the NFPA’s statistics because the impact of the planes destroyed much of the sprinkler systems’ ability to operate.)
Explainer thanks Gary Tokle of the National Fire Protection Association, Mark Bromann of Rally Fire Protection Services,and reader Peter Brown for submitting the question.
