Cable “Fireproof Coat”: The Invisible Guardian Protecting the Lifeline of Electricity
How can a special coating, less than a millimeter thick, create a miraculous escape from blazes?
In modern buildings, subway tunnels, industrial plants, and other places, cables, like the human body’s blood vessels, carry the core task of transmitting electrical energy. Once caught in a fire, these seemingly ordinary cables can become “invisible drivers” of fire spread. Their outer plastic layer rapidly melts and decomposes at high temperatures, releasing large amounts of heat and toxic fumes. Approximately 40% of the smoke and carbon monoxide in building fires comes from cable combustion.
Even more dangerously, flames can quickly spread along cable lines, damaging the power supply system and causing firefighting equipment to lose power, creating a vicious cycle of “fire spread, power outage, and firefighting failure.”
Coating cables with fireproof coatings is like draping these “lifelines” of electricity with a protective armor less than a millimeter thick. This microscopic line of defense received a technological upgrade in 2025: the newly released national mandatory standard GB 28374-2025 “Fire-retardant Coatings for Cables” will be implemented in June 2026, providing a stronger barrier for cable safety.
The Deadly Threat of Cable Fires
The outer layer of cables is typically made of plastics (such as PVC and polyethylene). In a fire, these materials serve not only as fuel but also as deadly gas generators. When heated, they decompose, releasing toxic gases such as hydrogen chloride and dioxins. Over 70% of casualties in fires are caused by asphyxiation or poisoning from smoke.
In high-rise buildings, the conduit shafts where cables are laid act as natural “chimneys,” accelerating the vertical spread of flames and smoke. Statistics show that in cable fires without fire prevention measures, the average fire spreads more than three times faster than that of ordinary combustible materials, and widespread combustion can occur in just minutes.
The Scientific Defense Mechanism of Fire Retardant Coatings
The protective power of fire retardant coatings stems from their sophisticated chemical composition and physical structure. When exposed to flames, the coating’s aluminum hydroxide, expanded graphite, and other substances immediately activate a triple defense mechanism:
- Flame Retardancy and Smoke Suppression: Absorbs heat and releases flammable gases, catalyzing the formation of a dense carbon layer on the plastic surface, reducing toxic smoke emissions by over 50%.
- Heat Insulation and High-Temperature Resistance: At temperatures above 200°C, the intumescent coating rapidly expands to 50 times its original volume, forming a porous carbon layer that can isolate flames exceeding 800°C.
- Circuit Integrity Guarantee: In critical locations like data centers and hospitals, emergency lighting, smoke exhaust systems, and other circuits remain operational for over two hours, creating prime time for evacuation.
Technical Upgrades Under the New National Standard
**GB 28374-2025 “Fire Retardant Coatings for Cables,” released in July 2025, sets higher standards for cable fire protection. The new standard stipulates that flame retardancy testing requires measuring the charring height of the cable after a 40-minute continuous burning period. It also specifies:
- Charring height measurements must be accurate to two decimal places
- Key information such as the test substrate type and coating thickness must be fully recorded
- The coating must pass the “hydrocarbon fire test”—which simulates the sudden increase in temperature experienced by petrochemical fires—without peeling or failure within 30 minutes.
These stringent requirements are driving companies to develop higher-performance products. For example, ceramic-based fire-retardant coatings, which can withstand temperatures of 1200°C, are specifically designed for use in refineries and nuclear power plants; and water-based environmentally friendly coatings, suitable for confined spaces like subways and shopping malls, to prevent chemical contamination in the early stages of a fire.
Precision Application Techniques
The effectiveness of fire-retardant coatings is highly dependent on standardized application procedures:
- Surface Treatment: Thoroughly remove dust and oil stains from the cable surface, ensuring the substrate is dry and clean.
- Layered Coating: For plastic or rubber-sheathed cables, apply directly to the cable with at least five applications, leaving 24 hours between each application.
- Thickness Control: The final coating thickness should reach 0.5-1mm (approximately 1.5kg/m² of coating consumption).
- Special Treatment: Oil-paper insulated cables should be wrapped with glass cloth before coating. In humid environments, a topcoat varnish should be applied.
It is important to note that while the coating is still wet, it must be strictly protected from water, sunlight, and bending. Any damage can become a fatal weakness in the fire protection chain.
Economic and Environmental Advantages
Compared to traditional protection measures such as fire-resistant troughs and fire-resistant bridges, applying fire-retardant coatings can increase cable current carrying capacity by 15%-20%, avoiding the increased energy consumption associated with enclosed protection. In a 2020 data center fire, cables coated with fire-retardant coatings protected 80% of servers not exposed to direct flames, preventing economic losses exceeding 200 million yuan.
Environmentally friendly coatings also offer ecological benefits: water-based environmentally friendly coatings achieve low VOC emissions, while the integrated anti-corrosion and fire-resistant coating used on submarine cables protects against both seawater erosion and welding sparks, significantly extending the cable’s service life.
Home Improvement Safety Upgrade Options
Low-smoke, halogen-free, flame-retardant electrical wiring is becoming the new safety standard for home renovations. Made of polyolefin, this type of wiring boasts a smoke transmittance exceeding 50% during combustion (compared to 20% for standard PVC wiring) and releases less than 0.5% hydrogen chloride gas, reducing the risk of toxic gases by over 90% compared to traditional wiring.
For families with elderly, children, or those with respiratory problems, this means significantly longer fire escape times. Twelve cities, including Beijing and Shanghai, have introduced subsidies of up to 5% of the total renovation cost for homes equipped with this type of wiring to promote safety upgrades.
概要
A fire-retardant coating, thinner than a coin, provides a lifeline against blazing flames. From the newly released national mandatory standard GB 28374-2025, to the strict requirements for cable channel construction in Chengdu’s “Two Guidelines and One Method,” to the widespread adoption of low-smoke, halogen-free wiring in home renovations, China is building a multi-level fire protection system for cables.
When the fire-retardant coating solidifies on the cable surface, it becomes more than just a line of technical specification; it embodies the safety philosophy of “preventing disasters before they occur.” This microscopic barrier, invisible to the naked eye, will become an invisible guardian in times of crisis, safeguarding the lifeblood of modern society’s electricity supply—because the most reliable safety often lies in the mere millimeters of forethought before disaster strikes.
よくあるご質問
Q1: Why are cables dangerous in fires?
A: Burning cables release toxic smoke (causing 70% fire deaths) and accelerate flame spread 3x faster.
Q2: How does fireproof coating work?
A: It expands 50x at 200°C, forms heat-insulating char layer, and cuts toxic smoke by 50%.
Q3: What’s new in GB 28374-2025 standard?
A: Requires hydrocarbon fire tests (1200°C), 40min burn resistance, and precise carbonization records.
Q4: Is this coating suitable for homes?
A: Yes. Low-smoke cables (50%+ light transmittance) with coatings reduce toxins by 90% for safer escapes.
Q5: How thick is the fireproof layer?
A: Only 0.5-1mm thick (1.5kg/m²), but withstands 800°C for 2+ hours.