To quickly decipher fire‑protection engineering drawings, start by gaining a solid understanding of the classification and components of fire‑protection systems. Carefully study the site plan, then review the drawing’s design notes and legend—pay particular attention to the various symbols, which you’ll need to memorize. After that, move on to the system diagrams; with a bit of time and practice, you’ll find it easy to follow. Of course, there are specific techniques for reading fire‑protection drawings, which we’ll explain in detail below.

Methods for Reading Fire Protection Drawings:

(1) Fire protection drawings are categorized into fire water systems, fire electrical systems, and gas-based fire suppression systems.

(2) Regardless of the type, every set of drawings should first be reviewed for the design notes and legend.

(3) The design description serves as an outline for the drawings; understanding it enables one to grasp the design intent and content.

(4) Different designs may have different legends;

(5) Next is the system diagram, which serves as the table of contents for the entire book. By understanding it, you can grasp the overall operational status and interconnections of the system.

(6) Finally comes the floor plan, which is essentially a further refinement of the system diagram, specifying the installation methods, locations, and connection details of the equipment.

(7) Note: When interpreting the drawings, compare the floor plan with the system diagram to integrate the entire system.

First, let’s briefly review the classification and components of fire protection systems:

Automatic Sprinkler Fire Suppression System:

According to the type of sprinkler used, automatic water spray fire suppression systems can be classified into two major categories: closed‑type automatic water spray fire suppression systems and open‑type automatic water spray fire suppression systems.

Depending on the system’s intended application and configuration, automatic sprinkler systems are further classified into wet‑pipe systems, dry‑pipe systems, preaction systems, deluge systems, water curtain systems, and combined automatic sprinkler–foam systems. The classification of automatic sprinkler systems is shown in the figure.

Wet automatic sprinkler fire suppression system (Hereinafter referred to as the wet system) it consists of closed‑type sprinkler heads, a wet‑type alarm valve assembly, a water flow indicator or pressure switch, water supply and distribution piping, and water supply equipment. In the standby condition, the piping is filled with pressurized water that serves to activate the system.

Dry Automatic Sprinkler System (Hereinafter referred to as the dry‑pipe system) it consists of closed‑type sprinkler heads, a dry‑pipe alarm valve assembly, water flow indicators or pressure switches, water supply and distribution piping, air‑charging equipment, and water supply facilities. In the pre‑action state, the distribution piping is filled with pressurized gas that serves to initiate the system.

The operating principle of a dry‑pipe system is similar to that of a wet‑pipe system; the only difference is that the medium used to transmit the open‑signal from the sprinkler heads is pressurized gas instead of pressurized water.

Pre-action automatic sprinkler system (Hereinafter referred to as the pre-action system) consists of closed‑type sprinkler heads, a deluge valve assembly, a water‑flow alarm device, water supply and distribution piping, air‑charging equipment, and water supply facilities. In the standby condition, the distribution piping remains unfilled with water; upon automatic activation of the deluge valve by the fire‑alarm system, the system transitions to a wet‑pipe configuration.

The key difference between a pre-action system and wet or dry systems is that the former employs a deluge valve and is equipped with an automatic fire alarm system.

Deluge system It consists of open-type sprinklers, deluge valve assemblies, water-flow alarm devices, water supply and distribution piping, and water supply facilities.

The difference from the previous systems is that:

The deluge system employs open-type sprinklers, with the spray pattern controlled by a deluge valve. The deluge valve is activated either by the associated automatic fire alarm system or by a transmission‑pipe system.

Deluge systems can be controlled electrically, hydraulically, or pneumatically.

Water curtain system It consists of open‑type sprinkler heads or water curtain nozzles, a deluge alarm valve assembly or a heat‑activated deluge valve, water supply and distribution piping, control valves, and a water‑flow alarm device (such as a flow indicator or a pressure switch).

Unlike the preceding systems, the water curtain system does not have direct fire-extinguishing capability; it is used to contain smoke and prevent flame spread, as well as to cool compartmentalization elements.

After installing equipment to supply foam‑water mixtures, an automatic water–foam combined system capable of delivering both water and foam is formed.

Classification and Components of Gas Fire-Extinguishing Systems:

According to the method of application, they can be classified into two types:

1. Total flooding fire suppression system;

2. Local application fire suppression system.

Next, we will introduce the respective characteristics of these two fire suppression systems:

1. Total Flooding Fire Suppression System

A total flooding fire suppression system is one in which a gaseous extinguishing agent of a specified concentration is discharged into the protected area within a prescribed time, uniformly filling the entire space. The nozzles of such a system are evenly distributed across the ceiling of the protected area. Upon the occurrence of a fire, the discharged extinguishing agent mixes with the air to rapidly establish an effective extinguishing concentration throughout the space and maintains that concentration for the required duration, thereby suppressing the fire by inundating the enclosed space with the gaseous extinguishing agent.

2. Local Application Fire Suppression System

A localized application fire suppression system is a system that, within a specified time period, delivers gas to the protected object at a designed discharge rate, creating a locally high concentration of extinguishing agent around the object and maintaining it for a predetermined duration.

In a localized application fire suppression system, the sprinklers are evenly distributed around the protected object. When a fire occurs, the extinguishing agent is discharged directly and in a concentrated manner onto the object, enveloping its entire external surface and achieving a high concentration of extinguishing gas within the localized area surrounding the object to effect fire suppression.

Classification by pressurization method:

Fire suppression systems, classified according to their pressurization method, can be divided into three types:

1. Self-pressurized gas fire suppression system

A self‑pressurized gas fire‑extinguishing system is one in which the extinguishing agent is conveyed without external pressurization, relying instead on its own saturated vapor pressure.

2. Internally Pressurized Gas Fire-Extinguishing System

An internally pressurized gas fire-extinguishing system is a fire-extinguishing system in which the extinguishing agent is stored under pressure with an inert gas within the cylinder assembly, and upon activation, the agent is discharged by the pressurizing gas contained in the cylinder assembly.

3. Externally Pressurized Gas Fire-Extinguishing System

Finally, we will explain the externally pressurized gas fire suppression system:

An externally pressurized gas fire-extinguishing system is one in which, upon activation, the extinguishing agent is charged to its design pressure by a dedicated pressurizing gas cylinder assembly.

System composition:

Above, we discussed the classification of fire suppression systems. Next, we will examine the components of such systems, which can be divided into five categories:

(1) High-pressure carbon dioxide fire suppression systems and internally pressurized heptafluoropropane fire suppression systems

(2) Externally Pressurized Halon-1301 Fire Suppression System

(3) Inert Gas Fire-Extinguishing System

(4) Low-pressure carbon dioxide fire suppression system

(5) Pipeless Fire Suppression System

Below, we will provide a detailed introduction to these five system components:

(1) High-pressure carbon dioxide fire suppression systems and internally pressurized heptafluoropropane fire suppression systems

First, let us introduce the high-pressure carbon dioxide fire suppression system and the internally pressurized heptafluoropropane fire suppression system:

Such systems comprise an extinguishing agent cylinder assembly, a driver gas cylinder assembly (optional), check valves, selection valves, actuating devices, manifolds, connecting pipes, nozzles, signal feedback devices, safety relief devices, control panels, leak detection devices, piping components, and hanger brackets, among other elements.

(2) Externally Pressurized Halon-1301 Fire Suppression System

The system comprises a fire‑extinguishing agent cylinder bank, a pressurizing gas cylinder bank, an optional driver‑gas cylinder bank, check valves, selection valves, pressure‑reducing devices, actuating devices, manifolds, connecting pipes, nozzles, signal feedback devices, safety relief devices, a control panel, leak‑detection devices, pipeline fittings, and hanger brackets, among other components.

(3) Inert Gas Fire-Extinguishing System

An inert gas fire suppression system consists of an extinguishing agent cylinder assembly, a driver gas cylinder assembly (optional), check valves, selection valves, pressure-reducing devices, actuating devices, manifolds, connecting pipes, nozzles, signal feedback devices, safety relief devices, control panels, leak detection devices, piping components, and hanger brackets, among other elements.

(4) Low-pressure carbon dioxide fire suppression system

   

The system comprises a fire-extinguishing agent storage unit, a master control valve, actuators, spray nozzles, pipeline overpressure relief devices, signal feedback units, and a controller, among other components.

(5) Pipeless Fire Suppression System

The pipeless fire suppression system is further divided into two types of installation systems, namely:

1. Cabinet-type gas fire suppression system;

2. Suspended gas fire suppression system.

Next, we will introduce the characteristics of these two fire suppression systems, one by one.

1. Cabinet-type gas fire suppression system

The system typically comprises an extinguishing-agent cylinder assembly, a driver-gas cylinder assembly (optional), container valves, a pressure-reducing device (for inert-gas fire-extinguishing systems), a driving mechanism, a manifold (applicable only to multi-cylinder assemblies), connecting pipes, nozzles, a signal‑feedback device, a safety relief device, a control panel, a leak‑detection device, and pipeline fittings, among other components.

2. Suspended Gas Fire Extinguishing System

The device consists of a fire-extinguishing agent storage container, an actuation and release assembly, a suspension bracket, and other components.

How can you quickly and easily understand fire safety drawings at a glance?

Fire protection engineering drawings are typically divided into plumbing and drainage systems (including automatic sprinkler systems, fire hydrants, and gaseous fire suppression) and electrical systems (including automatic fire alarm systems). In some cases, the project owner may also assign the smoke control and exhaust portion to the fire protection contractor. Fire protection budgets are categorized by discipline, and the installation costs for specific equipment can be found in the relevant fire protection installation rate schedules.

(1) For example, sprinkler heads, water spray piping, supports and hangers, fire hydrants, alarm valves, detectors, modules, and alarm devices; other general components shall be priced according to the relevant trade-specific rate schedules.

(2) For example, the installation of fire hydrant piping is billed under the plumbing and drainage pipeline quota; the piping installation in pump rooms falls under the industrial piping quota; the installation of fire pumps is charged according to the mechanical equipment installation quota; valve and flange installation is covered by the industrial piping quota; and the conduit installation for the alarm system is billed under the electrical installation quota, and so on.

(3) Material calculation: The number of equipment items can be determined based on the drawing quantities, while piping and conduit details will need to be finalized independently.

Fire detector and alarm characteristic notation:

Regional Alarm System:

Control Center Alarm System:

GA/T 227–1999 Method for Coding Fire Detector Product Models:

Fire detector classification code:

Application Scope Characteristics:

Sensitivity mode of the heat fire detector:

Characteristics of the sensing element of a heat‑sensitive fire detector:

Smoke detector, flame detector, and combustible gas detector sensor characteristic notation:

Composite fire detector sensor feature representation:

Example of fire detector product model designation:

a. JTW‑JD‑Ⅰ fusible alloy fixed‑temperature fire detector, Class I sensitivity;

b. JTW-SC bimetallic differential-temperature fire detector;

c. JTW-ZCD-Ⅲ thermistor differential‑temperature fire detector, Class III sensitivity;

d.JTYC-LZ marine ionization smoke fire detector.

e.JTGB-ZW explosion-proof ultraviolet flame detector;

f. JTF-YM composite smoke and heat fire detector;

g. JTF-YW-HS composite infrared beam smoke and heat fire detector;

h.JTY-LZ-C ionization smoke fire detector (third modification).

Fire alarm product model:

Application Scope Characteristics:

Classification feature code:

Structural feature code:

System Diagram:

Basic Graphic Symbols and Engineering Legend for Fire Protection Engineering:

(1) Fire protection engineering fire extinguisher symbol

(2) Symbols for Fixed Fire Extinguishing Systems in Fire Protection Engineering

(3) Symbols for Automatic Fire Alarm Equipment in Fire Protection Engineering

(4) Symbols for the installation locations of fire suppression equipment in fire protection engineering

(5) Basic graphical symbols for fire protection engineering

(6) Auxiliary Symbols for Fire Protection Engineering

(7) Symbols for Fire Protection Piping and Fittings

What do XL, WL, TL, JL, FL, PL, GL, and NL mean in fire protection drawings?

In fire protection drawings, XL denotes the fire‑fighting riser, WL denotes the sewage riser, TL denotes the vent riser, JL denotes the water supply riser, FL denotes the wastewater riser (fecal‑discharge riser), PL denotes the drainage riser (or GL), and NL denotes the air‑conditioning condensate riser.

For example, XL-1, XL-2, and XL-3 indicate which item they refer to.

XL stands for X, which represents firefighting.

L stands for riser; similarly, WL denotes wastewater. For example, if the drawing indicates XL-45, it refers to a fire‑fighting riser with identification number 45.

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