May I ask if polyurethane foam can be used as a type B cold-insulating material? Will it catch fire?

If there’s no manual, one can only rely on everyone’s experience

Polyurethanes do not have good flammability, unless they catch fire due to high temperatures. However, due to certain differences in their specific composition, they are not true flame-retardant materials, and they tend to decompose at high temperatures to release highly toxic cyanofluoric acid, which limits their use in certain applications. Flame-retardant polyurethane materials are also in use nowadays.

First, let’s provide some basic information on fire resistance ratings. According to the **standard GB8624-2012**, there are currently 5 main grades for fire-resistant materials: Grade A1: non-flammable, does not produce an open flame； Level A2: Non-flammable; smoke measurement is required, and it must pass the test ； Level B1: Flame-retardant building materials: Materials of this category have good flame-retardant properties. It is difficult to catch fire when exposed to an open flame in air or under high temperatures, and does not spread rapidly; moreover, the burning stops immediately once the heat source is removed ； Level B2: Flammable building materials: Flammable materials have a certain degree of flame-retardant properties. They will catch fire immediately when exposed to an open flame in the air or under high temperatures, and can easily lead to the spread of fires; examples include wooden columns, wooden roof trusses, wooden beams, wooden stairs, etc. Category B3: Flammable building materials with no flame-retardant properties at all; they burn very easily and pose a high risk of fire. Several commonly used insulation materials available on the market today, such as polyurethane (PUR), PIR, Alesse from Germany, and Fulose from Italy, all have a fire resistance rating of B1. However, although PUR is the cheapest option, it is being used less and less these days; one of the reasons for this is what was mentioned in point 3 – polyurethane (PUR) tends to decompose at high temperatures to produce highly toxic cyanuric acid. In accordance with **Standard GB50264-2013 \"Code for Design of Thermal Insulation of Industrial Equipment and Piping\", Article 4.1.6: The combustion performance grade of thermal insulation materials and products shall meet the following requirements: 1. When the surface temperature of the equipment or piping to be insulated is greater than 100°C, materials of grade A2 or higher as specified in the **Standard \"Classification of Combustion Performance of Building Materials and Products\" GB 8624 shall be used. 2. When the surface temperature of the insulated equipment or pipes is less than or equal to 100°C, materials of grade C or higher as specified in the standard **\"Classification of Combustibility of Building Materials and Products\" GB8624 should be selected. When materials of grades B and C specified in the standard **\"Classification of Combustibility of Building Materials and Products\" GB8624 are used, the oxygen index should be no less than 30%. So for the Class B media you inquired about, B1-grade fire-resistant insulation materials such as polyurethane can be used. I hope the answer above is helpful to you.