Technical Articles

Is B1 or B2 fire rated foam?


Fire safety is a crucial aspect of building construction, and choosing the right materials plays a vital role in ensuring the safety of occupants. One such material is fire-rated foam, which is designed to resist the spread of flames in case of a fire. In this article, we will delve into the differences between two common classifications of fire-rated foam known as B1 and B2. By understanding their properties, applications, and testing standards, we can make informed decisions when it comes to selecting the appropriate fire-rated foam for specific construction projects.

The Distinction: B1 versus B2

B1 and B2 are fire resistance ratings assigned to foams based on their ability to withstand exposure to fire and limit its spread. These classifications are determined through extensive testing methods specified by regulatory bodies. While both B1 and B2 fire-rated foams offer some degree of fire resistance, they differ in terms of their composition, chemical properties, and performance characteristics.

B1 fire-rated foam, often referred to as "hard foam" or "building foam," contains flame-retardant additives that prevent flames from quickly spreading. This type of foam is commonly used in applications that require higher fire safety standards, such as insulation for walls, ceilings, and air ducts. B1 foam offers superior resistance to flame penetration and releases lower levels of smoke and toxic gases during a fire event.

On the other hand, B2 fire-rated foam, also known as "soft foam" or "household foam," possesses a slightly lower fire resistance compared to B1 foam. It is typically used in less critical areas or residential settings where stringent fire regulations may not be mandatory. B2 foam exhibits moderate flame retardancy capabilities and emits a higher amount of smoke and toxic gases when exposed to fire.

Testing Standards

To ensure the reliability and consistency of fire-rated foams, several testing standards have been established. These standards evaluate the foam's resistance to ignition, flame spread, smoke production, and toxicity levels. The most commonly used tests include the B-series tests, vertical burn tests (UL 94), and the cone calorimeter test (ISO 5660).

The B-series tests determine the foam's classification by measuring its ability to propagate flames across its surface. B1 foam must resist both vertical and horizontal flame propagation, whereas B2 foam only needs to inhibit vertical flame spread. The vertical burn test focuses on assessing the material's self-extinguishing characteristics, while the cone calorimeter test measures heat release rate and other combustion-related properties.


Choosing the appropriate fire-rated foam, whether it is B1 or B2, depends on the specific requirements and regulations of a given construction project. While B1 foam offers superior fire resistance and safety features, B2 foam may be suitable for less demanding applications. It is crucial to consider factors such as the type of building, its occupancy, and local fire safety codes when making a decision.

Ultimately, prioritizing fire safety by incorporating reliable fire-rated foams ensures the protection of lives and properties in the event of an unfortunate fire incident.



Contact: Eason Wang

Phone: +86-13751010017


Add: 1F Junfeng Building, Gongle, Xixiang, Baoan District, Shenzhen, Guangdong, China

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