Fire sprinklers are crucial for controlling fires and protecting both property and lives. Selecting the right type of fire sprinkler head is essential for maximum effectiveness.
Fire sprinklers are classified by factors such as heat-sensitive elements, installation orientation, thermal sensitivity, coverage area, and performance characteristics. For example, the most commonly used pendent sprinkler can be described as a standard response, 68°C, glass bulb model with standard coverage. These classifications highlight key attributes, helping you select the right sprinkler for specific fire protection needs.
Table of Contents
Classification by Heat-Sensitive Element
Glass Bulb Sprinkler
The glass bulb sprinkler features a glass bulb filled with a heat-sensitive liquid. When exposed to heat, the liquid expands, causing the bulb to break and activate the sprinkler. This simple, reliable mechanism is widely adopted due to its cost-effectiveness and ease of installation. The glass bulb design is commonly used in residential, commercial, and industrial fire protection systems, making it a preferred choice for most applications due to its low maintenance and proven performance.
Fusible Link Sprinkler
In a fusible link sprinkler, a metal link serves as the heat-sensitive element. When the link melts at a specific temperature, it triggers the sprinkler valve to open. Known for its robust construction and high-pressure tolerance, fusible link sprinklers are ideal for larger sprinkler heads, such as K363 ESFR sprinklers. These types of sprinklers are often found in industrial and high-hazard environments, including warehouses and storage facilities, where large volumes of water and rapid suppression are necessary.
* Does Fusible Link Perform Better Than Glass Bulb in Low Temperatures?
There is a common misconception in the fire protection industry that fusible links perform better than glass bulbs in low-temperature environments. However, this is not true. According to the GB5135.1-2019 sprinkler standard in China, both glass bulb and fusible link sprinklers must meet the same low-temperature tolerance requirement of -30±5℃.
The test involves placing sprinkler samples in a low-temperature chamber at -30°C for 24 hours, then thawing them and checking for any visible damage. After ensuring no visible damage, a water pressure test is conducted to verify if the sprinklers leak. If there is no leakage, the sprinkler passes the low-temperature test.
In reality, both types of sprinklers—whether glass bulb or fusible link—are designed to function at -30°C without issue, as long as the sprinkler system is correctly installed and insulated. The failure of sprinklers in freezing temperatures is typically due to improper system selection or lack of insulation, which causes the water in the pipes to freeze. When this happens, the expanding ice creates pressure, potentially damaging both types of sprinklers, and leading to leaks once the system thaws. Proper insulation and system maintenance are key to preventing such failures, regardless of the heat-sensitive element used.
Classification by Installation Orientation
Upright sprinkler
Upright sprinklers are installed above the pipe, with the sprinkler head facing upwards. The water spray is directed upward toward the deflector, which then disperses the water downward to cover the area below. These sprinklers are ideal for spaces without ceilings or when the branch pipes are mounted below beams, as they provide optimal coverage in such environments.
Pendent sprinkler
Pendent sprinklers are installed below the pipe, with the sprinkler head hanging downward. The water spray is directed downward toward the deflector, which then disperses the water in a pattern designed to effectively cover the area beneath. This type of sprinkler is the most commonly used and is ideal for standard ceiling installations in both commercial and residential spaces.
Sidewall sprinkler
A sidewall sprinkler is mounted on the wall and features a special deflector designed to direct water in a pattern resembling a quarter of a sphere. Most of the water is discharged away from the nearby wall, with a small portion aimed at the wall behind the sprinkler. This type of sprinkler is commonly used in spaces with horizontal ceilings, such as light-hazard or medium-hazard areas, including residential buildings, dormitories, hotel rooms, medical wards, and office spaces.
Recessed sprinkler
A recessed sprinkler features a design where the body, except for the shank thread, is mounted within a recessed escutcheon that is embedded into the ceiling. This setup allows the sprinkler to blend seamlessly into the ceiling for a more aesthetically pleasing appearance while still providing effective fire protection. Recessed sprinklers are commonly used in spaces where a clean, unobtrusive look is preferred, such as upscale offices, hotels, and residential areas.
Concealed sprinkler
A concealed sprinkler is a recessed sprinkler equipped with a decorative cover plate. Once installed, the cover plate is flush with the ceiling, offering a clean design. Upon activation, the cover plate falls away, exposing the sprinkler head, which then responds to the heat and activates to suppress the fire. Concealed sprinklers are typically recommended for light and ordinary hazard areas (Class I), where they combine effective fire protection with a pleasing appearance.
Flush sprinkler
A flush sprinkler is designed so that part of the body, including the shank thread, is mounted above the ceiling’s lower plane, while the heat-sensitive element remains entirely below the ceiling. This setup allows the sprinkler to be mostly concealed, providing a clean, aesthetically pleasing look without compromising fire protection performance.
The cover plate hides the ceiling’s opening, making it ideal for environments where design is a priority, such as luxury hotels, upscale restaurants, and high-end commercial spaces. In addition to its decorative function, a flush sprinkler is particularly suitable for areas with low ceilings, where exposed sprinklers might be at risk of damage. Moreover, because the heat-sensitive element is aligned with the ceiling plane and remains below it, flush sprinklers respond quickly in the event of a fire, unaffected by the cover plate. This feature makes them more versatile and widely used compared to concealed sprinklers.
Classification by Thermal Sensitivity
Standard response sprinkler
With an RTI of 80 or more (m·s)¹/²(basically 80-350 (m·s)¹/²), these sprinklers are designed primarily for property protection. Their slower activation allows them to pre-wet materials near the fire, controlling its spread and preventing further damage. They are best used in areas where the goal is to contain the fire without risking rapid escalation, such as in industrial facilities or warehouses.
Special response sprinkler
These sprinklers fall within an RTI range of 50–80 (m·s)¹/², offering a balance between speed and control. They combine features of both Standard and Fast Response sprinklers, providing moderate activation speed suited for environments where both property protection and life safety are important. Special Response sprinklers are often used in mixed-use buildings or settings with unique fire suppression needs.
Fast response sprinkler
Sprinklers with an RTI of 50 or less (m·s)¹/² activate quickly to suppress fires, significantly reducing the risk of flashover. This makes them ideal for high-risk environments where life safety is the top priority. Their quick response provides precious time for occupant evacuation and helps prevent rapid fire spread, making them perfect for healthcare facilities, schools, and residential buildings.
| Sprinkler Type | RTI Range |
| Fast Response(Quick Response) | ≤ 50 (m·s)¹/² |
| Special Response | 50–80 (m·s)¹/² |
| Standard Response | 80-350 (m·s)¹/² |
Classification by Coverage Area
Standard coverage
These sprinklers are designed to protect areas up to 20 m² per sprinkler for pendant or upright types, and up to 18 m² for sidewall sprinklers. However, the maximum coverage area for any sprinkler should not exceed 20 m². Upright and Pendant Sprinklers are suitable for all occupancy hazard classifications and building construction types. Sidewall sprinklers are limited to specific conditions such as light or order hazards with smooth ceilings.
Extended coverage
These sprinklers provide coverage for larger areas, with each unit protecting an area greater than that of a standard coverage sprinkler, but not exceeding 36 m². Extended coverage sprinklers are ideal for spaces with level ceilings, where no beams, ducts, or other obstructions interfere with the sprinkler’s water distribution. They are particularly useful in large, unobstructed areas, reducing the number of sprinklers required.
| Sprinkler Type | Maximum Coverage | Applications |
| Standard Coverage | 20m2 for upright and pendent sprinklers18m2 for sidewall sprinklers | Widely used in almost all occupancy hazards |
| Extended Coverage | 36m2 | Specially used in unobstructed construction with smooth ceilings |
Classification by Functional Characteristics
Control Mode Density Area (CMDA) Sprinkler
CMDA sprinklers are designed for storage applications, providing fire control based on specific density/area requirements. They are typically used in warehouses and storage facilities to control the spread of fire over large areas.
Control Mode Specific Application (CMSA) Sprinkler
These sprinklers produce large water droplets and are specifically designed for high-challenge fire hazards. They are effective in environments where standard sprinklers might not provide adequate suppression, such as in areas with highly flammable materials or chemical storage.
Early Suppression Fast-Response (ESFR) Sprinkler
ESFR sprinklers are fast-acting with a thermal element that has a rapid response time (RTI ≤ 50). These sprinklers are ideal for high-hazard applications where quick suppression is essential to prevent flashover. They are often used in high-ceiling warehouses, factories, and storage areas with flammable materials.
Intermediate-Level Sprinkler/Rack Storage Sprinkler
These sprinklers are designed for rack storage environments, and equipped with integral shields that protect the sprinkler’s operating elements from water discharged by sprinklers above. They are commonly used in multi-level storage facilities and high-rise buildings with stacked storage.
Dry Sprinkler
Dry sprinklers are installed in systems where water is prevented from entering the pipes until activation. These sprinklers are typically used in areas where pipes are subject to freezing, such as unheated spaces like warehouses, attics, or cold storage rooms. They remain dry until needed, ensuring water does not freeze in the system.
Corrosion-Resistant Sprinkler
These sprinklers are built from corrosion-resistant materials or treated with special coatings to withstand harsh, corrosive environments. They are commonly used in outdoor installations, chemical plants, or areas exposed to harsh weather conditions that could deteriorate standard sprinklers.
Electrically Operated Sprinkler
Electrically operated sprinklers are equipped with a mechanism that activates via electricity rather than relying on heat or mechanical components. These sprinklers are used in specialized systems, such as data centers or high-tech facilities, where traditional sprinklers might not be ideal.
Conventional Sprinkler
Conventional sprinklers direct 40% to 60% of water downward and can be installed in either upright or pendent positions. They are used in commercial and residential buildings, offering effective fire protection for general areas with standard fire risks.
Open Sprinkler
Open sprinklers do not have actuators or heat-sensitive elements. They are typically used in special applications where constant water flow is required, such as irrigation systems or areas where a fixed water supply is necessary, rather than for traditional fire suppression.
Residential Sprinkler
Designed specifically for residential use, these fast-response sprinklers have a thermal element with an RTI ≤ 50. They are tailored for enhanced survivability in dwelling units and are designed to suppress fires in their early stages, protecting occupants from fire dangers in home environments. They are ideal for single-family homes, apartments, and hotels.
FAQ
What is the most common type of fire sprinkler?
The most common type of fire sprinkler is the standard pendent sprinkler. It hangs from the ceiling with the sprinkler head facing downward and is used in most commercial and residential buildings.
How to identify a fire sprinkler head?
The most straightforward way is to check the sprinkler’s deflector for markings that display key specifications such as the K-factor, deflector characteristics, pressure rating, and thermal sensitivity. You can also identify the sprinkler type by looking at its deflector design, which reveals whether it is an upright, pendent, or sidewall sprinkler. Additionally, the thermal element (such as a glass bulb) can help you determine the activation temperature based on its color.
What do SSP and SSU mean on a sprinkler head?
SSP and SSU are often marked on the deflector of the sprinkler head. SSP stands for Standard Spray Pendent, indicating a standard coverage pendent sprinkler. SSU stands for Standard Spray Upright, indicating a standard coverage upright sprinkler.
What do the different color sprinkler heads mean?
Sprinkler heads come in different colors to indicate their temperature ratings. For glass bulb sprinklers, the color of the bulb represents the activation temperature. For example, a red bulb indicates an activation temperature of 68°C, a yellow bulb for 79°C, and a blue bulb for 93°C. These color codes help identify the temperature at which the sprinkler will activate during a fire.
For more details about sprinkler color codes and temperature ratings, please refer to the blog “What is the Temperature Ratings of Fire Sprinkler Heads?”
What’s the difference between CMDA and CMSA sprinklers?
CMDA(Control Mode Density Area) sprinklers are designed for storage applications with specific density/area fire control, while CMSA(Control Mode Specific Application) sprinklers produce larger droplets and are for high-challenge fire hazards, offering more intense suppression in specialized areas.
How do I choose a fire sprinkler head?
Choosing a fire sprinkler head depends on the environment (e.g., warehouse or office), fire risk, and sprinkler coverage area. For high-occupancy areas, choose fast-response models, and for storage areas, select sprinklers designed for specific applications such as CMSA and ESFR sprinklers.
How effective are fire sprinkler systems?
Automatic fire sprinkler systems are widely recognized as one of the most effective fire suppression technologies. They are known for their reliability and high success rate in extinguishing fires. According to the National Fire Protection Association (NFPA), automatic fire sprinkler systems successfully suppress fires 96% of the time (as of early 2024).
How to choose escutcheons for sprinklers?
Choose escutcheons based on the size and type of your sprinkler heads, ensuring compatibility (e.g., 1/2’’ or 3/4’’). Consider the space’s design, budget, and local fire safety codes. Consulting a fire safety expert will help ensure the right selection for performance and compliance.
How to choose guards for sprinkler heads?
Ensure the sprinkler guard is compatible with your sprinkler head by matching the thread size (e.g., 1/2’’, 3/4’’, 1’’). Consider the environment—stainless steel guards are best for areas with high humidity or exposure to chemicals. For high-risk areas like warehouses or factories, opt for heavy-duty guards to protect against impacts.
Conclusions
Understanding the different classifications and performance parameters of fire sprinklers helps you make informed decisions when selecting the right sprinkler for your needs. Whether you’re designing a fire sprinkler system, purchasing fire equipment, or choosing individual sprinklers, knowing the specific functions and applications of each type ensures better fire protection.
