玻璃本身是不燃材料，但當(dāng)它作為圍護(hù)材料時(shí)由于火災(zāi)發(fā)生時(shí)的環(huán)境溫度高于玻璃的軟化點(diǎn)，玻璃圍護(hù)坍塌，已不能阻擋火勢(shì)，準(zhǔn)確地說(shuō)防火性能是取決于耐火極限。防火玻璃國(guó)家新標(biāo)準(zhǔn)《建筑用安全玻璃》（GB15763.1－2008）將防火玻璃的性能分為A類(lèi)和C類(lèi)。其中A類(lèi)為隔熱型防火玻璃，其耐火極限分0.5h，1.0h，1.5h，2.0h，2.5h，3.0h六個(gè)等級(jí)。C類(lèi)為非隔熱型防火玻璃，其防火時(shí)間設(shè)置了4個(gè)等級(jí)：0.5h，1.0h，2.0h，3.0h。所謂隔熱性防火玻璃是指其耐火性能同時(shí)滿足耐火完整性和耐火隔熱性的玻璃。如果只能滿足耐火隔熱性的就稱非隔熱性玻璃。
    U型玻璃的耐火極限為0.75h，當(dāng)不能滿足設(shè)計(jì)時(shí)可加貼防火膜或與平板銫鉀防火玻璃配合使用。

Glass itself is non-flammable material, but when it is used as enclosure material, because the ambient temperature is higher than the softening point of glass when the fire occurs, the glass enclosure collapses, which can not stop the fire. Precisely speaking, the fire resistance depends on the fire resistance limit. The new national standard of fire-proof glass, Safety Glass for Buildings (GB15763.1-2008), classifies the performance of fire-proof glass into A and C categories. Among them, Class A is heat-insulating fire-proof glass. Its fire resistance limit is divided into six grades: 0.5h, 1.0h, 1.5h, 2.0h, 2.5h and 3.0h. Class C is non-insulating fire-proof glass. Its fire-proof time is set up in four grades: 0.5h, 1.0h, 2.0h and 3.0h. The so-called insulating fireproof glass refers to the glass whose fireproof performance satisfies both fireproof integrity and fireproof insulation. If it can only meet the requirements of fire resistance and heat insulation, it is called non-insulating glass.

The fire resistance limit of U-shaped glass is 0.75h. When it can not meet the design requirements, it can be used with fire-proof film or with flat Cesium-Potassium fire-proof glass.