Different Types of Fire Sprinkler Systems as Defined by NFPA 13 

Fire sprinkler systems play a critical role in protecting lives and property by controlling or extinguishing fires in their early stages. The National Fire Protection Association (NFPA) 13, Standard for the Installation of Sprinkler Systems, categorizes these systems into several types, each designed for specific applications and conditions. Below, we provide an overview of each type of fire sprinkler system, highlighting their unique features and benefits as defined by NFPA 13. 

WET FIRE SPRINKLER SYSTEM 

A wet fire sprinkler system is the most common type of fire sprinkler system and can only be used in buildings with above-freezing temperatures. It consists of a network of pipes filled with pressurized water, and when a fire occurs, the heat activates the sprinkler heads, allowing water to be immediately discharged over the fire area.  

Advantages:

Immediate Response: Water is always available at the sprinklers, ensuring a quick response to fire. 

•  Simple Maintenance: With fewer components than other systems, wet systems are easier to maintain and test. 

Applications: 

• Suitable for environments where temperatures do not fall below freezing, such as residential buildings, office spaces, and retail stores. 

DRY FIRE SPRINKLER SYSTEM 

Dry fire sprinkler systems are ideal for areas where the ambient temperature can fall below freezing. Unlike wet systems, dry systems use pressurized air or nitrogen in the pipes. When a sprinkler is activated, the air is released, allowing water to flow into the pipes and out through the sprinkler to combat the fire. 

Advantages:

• Freeze Protection: The use of pressurized air prevents water from being in the pipes until needed, thus avoiding the risk of freezing. 
• Delayed Activation: There is a slight delay in water discharge as the air must first be expelled, but this is often a necessary trade-off in colder environments. 

Applications:

• Unheated buildings or sections of buildings, such as warehouses, loading docks, and attics. 

Key Considerations:

• Requires more maintenance and testing compared to wet systems due to additional components like air compressors and dry valves. 

PRE-ACTION FIRE SPRINKLER SYSTEM 

Pre-action sprinkler systems are designed to prevent accidental discharge of water, making them suitable for environments where water damage must be minimized. These systems require a two-step process to activate: the detection of a fire by a separate alarm system and the subsequent release of a valve that allows water to flow into the sprinkler pipes. Some areas where pre-action sprinkler systems may be desirable are computer server rooms and operating/surgery centers.  

Advantages:

• Reduced Risk of Water Damage: Only activated in response to a verified fire, minimizing the potential for accidental water discharge. 
•  Versatile Application: Suitable for both wet and dry systems, offering flexibility in different environments. 

Applications:

• Ideal for areas containing sensitive equipment or materials, such as data centers, libraries, and museums. 

Key Considerations: 

• More complex and costly than other systems due to the need for a separate detection system and pre-action valve.  

DELUGE FIRE SPRINKLER SYSTEM 

Deluge systems are designed for high-hazard areas where a rapid spread of fire is possible. These systems keep the pipes dry and feature open sprinkler heads. Upon fire detection, a deluge valve releases water, which flows through all open heads simultaneously, providing a large volume of water to the affected area. 

Advantages:

• Immediate and Comprehensive Response: Delivers a large amount of water quickly over a wide area, ideal for fast-growing fires. 
• Open Sprinklers: Allows for a broad coverage area, ensuring the entire space is protected once activated. 

Applications:

• High-risk areas such as chemical storage, aircraft hangars, and power plants where flammable liquids or gases are present. 

Key Considerations: 

• Requires careful design and maintenance to ensure proper activation and coverage. 

RESIDENTIAL 13R FIRE SPRINKLER SYSTEM 

An NFPA 13R sprinkler system is specifically designed for low-rise residential buildings. This is defined as a maximum of 4-stories in height or 60 feet or less above grade plane. These systems are tailored to provide life safety by controlling fires early and preventing flashover, allowing occupants more time to escape. 

Advantages:

• Life Safety Focus: Primarily aimed at preventing loss of life by ensuring that fires are controlled quickly. 
• Cost-Effective: Simplified design criteria for residential buildings reduce installation costs. 

Applications: 

• Suitable for residential occupancies up to four stories, such as apartment buildings, dormitories, and hotels. 

Key Considerations:

• Limited in application to certain residential structures and may not be suitable for commercial or industrial uses. 

Have an NFPA 25 Question? The NFSA is Here to Help

Understanding the differences between the different types of fire sprinkler systems and their appropriate applications is crucial for ensuring effective fire protection. The National Fire Sprinkler Association is committed to promoting fire safety and the proper use of sprinkler systems as outlined by NFPA 13.

If you have a question about ITM for fire protection systems, the NFSA is your resource. Whether it’s information on what the standard says or help with adopting it in your own jurisdiction, our team of experts can help you. For more information on membership, visit our join page.

Further Reading

Types of Fire Sprinkler Systems – NFPA