Flame-Resistant B1-Grade Cables: Vital for Buildings and Occupants

NOTE: The content in this blog is specific to the Asia Pacific region.

As the global population continues to grow, urban construction continues to rise. As a result, the number of highly occupied facilities, such as high-rise buildings, shopping centers, schools, subway stations, airports, sports centers, exhibition centers and hospitals, is also increasing. Together, these factors can accelerate the risk of fire.

Over the years, China has seen an uptick in fire incidents, some of which occurred in densely populated areas or facilities and caused significant casualties and property damage. By studying the causes of these events, industry experts are learning ways to help prevent similar incidents in the future.

The Role of B1-Grade Flame-Resistant Cable in Fire Protection

Combustible material applications in high-rise buildings call for the flame-retardant performance that B1-grade flame-resistant cables can provide.

These fire-resistant cables are designed for use in environments where fire safety is a significant concern.

• Burning-heat value
• Combustion growth rate index
• Flame spread
• Peak heat release rate
• Peak smoke production rate
• Smoke density
• Total heat release
• Total heat release rate
• Total smoke production
• Vertical flame spread
  
  

Based on their flame-retardant performance, cables are divided into four grades:

• Grade A: Noncombustible copper or fiber cable, equivalent to metal sheathed copper or fiber cable
  
  
• Grade B1: Flame-retardant Grade 1 copper or fiber cable, equivalent to low-smoke zero-halogen copper or fiber cable
  
  
• Grade B2: Flame-retardant Grade 2 copper or fiber cable, equivalent to low-smoke low-halogen copper or fiber cable
  
  
• Grade B3: Ordinary copper or fiber cable
  
  

In addition, GB 31247-2014 also assesses three additional properties based on the final products formed by insulation materials during combustion testing:

• Combustion droplets/particles (d)
• Smoke toxicity (t)
• Corrosiveness (a)

After evaluating the four flame-retardant grades mentioned above, the additional performance classification is determined for the cable.

When it Comes to Performance, Grade B1 Stands Out

While there are many grades of flame retardance, B1 stands out. The reason is this: It’s extremely difficult for B1-grade cables to ignite or burn in open-fire or high-temperature conditions. Their insulation materials are more difficult to carbonize, and fewer harmful substances are emitted during and after combustion.

Moreover, when the fire source is removed or extinguished, the combustion and micro-ignition of a B1-grade cable stops quickly; therefore, in terms of fire resistance, B1-grade cables could be listed as fire-resistant materials right alongside steel rebar and cement.

When it comes to the characteristics of cable during fire, Grade B1 is also more comprehensive than universal flame-retardant performance. It considers not only the cable’s ability to prevent and delay combustion but also the low-smoke and zero-halogen properties of the insulation materials.

Furthermore, B1-grade cable also takes into consideration thermal radiation performance after combustion, ignition ability and the emission of harmful substances, as well as the assessment of the impact of toxic substances to people.

Definitions for B1-Grade Cable Applications

More high-performance, flame-retardant Grade B1 cables are being applied in modern, densely populated facilities as the requirements for these types of projects become more detailed and standardized.

According to GB 51348-2019, Electrical Design Standard for Civil Buildings, issued by the Ministry of Housing and Urban Rural Development of People’s Republic of China, there are clear definitions of B1-grade cable applications.

Power Cables in Civil Buildings

For public buildings with a height exceeding 100 m, wires and cables should be selected with combustion performance of:

• Grade B1 or above
• Smoke toxicity of t0
• Combustion droplets/particles of d0
  
  

The exposed wires and cables in the refuge floor (room) should be selected with a combustion performance of no less than:

• Grade B1
• Smoke toxicity of t0
• Grade A cable
  
  

For Level 1 high-rise commercial buildings, such as financial buildings, provincial power distribution buildings, provincial (city)-level broadcasting and television buildings, telecommunication buildings, and high-traffic buildings, wires and cables should be selected with combustion performance of:

• Grade B1
• Smoke toxicity of t1
• Combustion droplets/particles of d1
  
  

Communication Cables and Optical Fibers in Structured Cabling Systems for Civil Buildings

Communication cables or optical fibers with grades higher than B1 should be applied in vertical applications in public buildings that have one of the following characteristics:

• Height equal to or higher than 100 m
• Height of less than 100 m but equal to or higher than 50 m
• Construction area greater than 100,000 sq m
• Level B or higher data center
  
  

For important public buildings, communication cables or optical fibers with grades higher than B1 should be applied in horizontal applications.

Cables for Automatic Fire Alarm Systems

Grade B1 wires and cables should be selected for alarm bus cable to support automatic fire alarm systems in evacuation routes for densely populated locations.

Pioneers of Grade B1 Cable Development

Grade B1 takes into account the safety of people and property. It has become a new trend in the construction industry and is highly recognized by industry experts.

Belden is proud to be the pioneer of Grade B1 cable development, offering Grade B1 flame-retardant control and power cables and Grade B1 flame-retardant fire-resistant cables.

Belden is the first manufacturer to develop B1-grade flame-retardant Category 6 and Category 6A network cables, which couple outstanding data transmission capabilities with extremely high flame-retardance and eco-friendly performance.

Related links:

• Products
• Markets
• Solutions