How Fire Sprinkler Systems Work: Dispelling Two Common Myths

Shubham More
Author : Shubham More
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    Automatic sprinkler systems are among the most reliable fire protection measures available for building interiors, and that is a key reason why Local Law 26 of 2004 makes them mandatory in many NYC buildings. Property owners are often skeptical about fire sprinkler installation, due to the perception that they cause widespread water damage when they activate. However, this is a misconception propagated by TV series and movies.

    There are two common myths about fire sprinklers, which are responsible for the negative public perception about them:

    • Myth #1: Fire sprinklers are activated by smoke, even in very small amounts.
    • Myth #2: They all activate at once, showering indoor spaces and everyone inside.

    In terms of water damage, it is better to have sprinkler heads activating than waiting for the NY Fire Department truck to arrive: the water volume from a fire hose is much higher than that from a sprinkler system. In fact, fire sprinkler systems contain most fires by themselves, before they have a chance to spread.

    Truth #1: Fire Sprinklers Activate with Heat

    Smoke and heat occur together during a fire, leading to the false perception that fire sprinklers activate with smoke. However, they really respond to heat, through the following process:

    • Fire sprinklers have a small glass bulb with a glycerin-based solution, which blocks the flow of water under normal conditions.
    • At temperatures between 135°F and 165°F, the solution expands to a point where it bursts the glass bulb open, releasing water under the sprinkler.
    • The flower-shaped diffuser sprays the water in the cone-shaped pattern that characterizes sprinklers.

    Another less common sprinkler head design uses a metal plug with an extremely low melting point, but the basic principle is the same: heat melts the metal, opening the sprinkler head and showering the area below with water.

    Truth #2: Fire Sprinklers Activate Individually

    Since each individual sprinkler has a mechanism that responds to heat, only those close the fire release water. In many cases, indoor fires are controlled by a single sprinkler head, while all others remain closed. In other words, your property will not suffer widespread water damage when the sprinkler system activates - the system targets the area where the fire is located. While water can damage some objects, allowing the fire to spread is worse.

    Keep in mind that the response speed of fire sprinklers can change depending on system configuration:

    • Wet pipe sprinkler systems have their piping filled with pressurized water. Therefore, water flows immediately when a sprinkler head activates.
    • Dry pipe sprinkler systems are filled with compressed air, and water is held back by a valve. The compressed air is released when a sprinkler head opens, allowing the water to flow.

    Wet pipe systems are simpler to install and have a faster response. They are the preferred option unless environmental conditions make it impractical to have the piping filled with water at all times. For example, water can freeze in very cold environments, rendering a wet pipe sprinkler system useless.

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    Special Applications Where the Two Sprinkler Myths Are True

    Deluge fire sprinkler systems are a subtype of dry pipe systems that work like those you have seen in the movies, showering an entire area in response to even minor signs of fire.

    • In a deluge system, all sprinkler heads are open but the piping is empty.
    • A valve controls the water supply for the entire system, and it activates when heat or smoke is detected.

    However, this type of fire sprinkler system is only used in high hazard applications where fire can have devastating and immediate effects, such as areas where combustible materials are stored. Deluge fire sprinkler systems are not used in residential and commercial applications precisely because they would case widespread water damage, and there is no need to shower the entire area.


    A properly-designed sprinkler system will protect your property and personnel from fire, while minimizing water damage. Keep in mind that NYC has some of the most stringent fire protection codes in the world, so a well-designed sprinkler system also ensures your project is approved for legal occupancy without hurdles.

    Smoke detectors and sprinkler heads work together to prevent life loss and minimize property damage due to fire. Consider that their functions are complementary: a smoke detector can activate an alarm and warn occupants about the presence of fire, but cannot quench it; on the other hand, sprinkler heads can extinguish a fire but cannot alert you.

    To make sure your property is well protected against fire and compliant with NYC codes, the best recommendation is getting professional assistance. You can contact our fire protection engineering experts to learn more.


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    Tags : Design Sprinkler design Fire sprinkler system Fire sprinkler myths Fire protection engineering

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