UNIALGLASS Fire-Rated Glass Withstands 68 Minutes — Exceeding Class E60 Requirements
At its accredited test facility, UNIALGLASS carried out fire tests of fire-rated glass for fire-resistance rating class E. A sample of borosilicate fire-resistant glass (BFL), measuring 2400 × 1200 mm and 8 mm thick, withstood the fire for 68 minutes — against the required standard of 60 minutes (class E60).
What class E60 means
The fire-resistance rating of transparent building envelope structures is denoted by letters indicating the limit states and the time in minutes. For glazing, the following are regulated:
- E — loss of integrity: the formation of through-cracks and openings, through which flame and combustion products penetrate to the unexposed side;
- I — loss of thermal insulation capacity due to heating (the average temperature rise of the unexposed surface exceeds 140 °C);
- W — the limiting heat flux density of 3.5 kW/m² is reached at a distance of 0.5 m from the unexposed surface.
For windows and non-load-bearing external (facade) walls, only integrity — class E — is regulated. The designation E60 means the limit state will not occur before 60 minutes. Our sample withstood 68 minutes, i.e. with a margin above the requirement.
How the tests are conducted and the internal temperatures involved
The test is carried out according to the methodology for transparent building envelope structures (GOST R 53308-2009, being replaced by GOST 30247.4-2022) together with the general requirements of GOST 30247.0. Both comply with the Russian national standard system (mandatory for the Russian market). The sample, at its design dimensions, is installed in the opening of the test furnace and subjected to one-sided heating. The moment of loss of integrity is detected using a cotton wool pad, which is applied to the areas where flame breakthrough is likely.
The furnace temperature rises according to the standard temperature curve of a «cellulosic» fire (ISO 834 curve), given by T = 345·lg(8t + 1) + T₀, where t is the time in minutes. According to GOST 30247.0, this corresponds to the following furnace values:
| Test time | Furnace temperature |
|---|---|
| 5 min | 556 °C |
| 15 min | 718 °C |
| 30 min | 821 °C |
| 60 min | 925 °C |
| 68 min (our result) | ~940 °C |
This means that by the 60th minute the glass retains its integrity at a furnace temperature of around 925 °C, and the UNIALGLASS sample maintained it for another 8 minutes beyond the requirement.
Update to the GOST standard for tempered glass
In 2025, Amendment No. 1 to GOST 30698-2014 «Tempered glass. Specifications» was introduced (order of Rosstandart, effective from the end of 2025). Complies with the Russian national standard GOST 30698-2014 (mandatory for the Russian market). The standard now includes the concept of «fire-resistant tempered glass» — tempered glass capable of withstanding thermal and mechanical loads during a fire for a specified time, preventing the spread of fire and combustion products, and the requirements for the fire-resistance rating have also been clarified. The test was carried out in accordance with the updated requirements.
Regulatory framework: GOST 30247.0-94, GOST R 53308-2009 / GOST 30247.4-2022, GOST 30698-2014 with Amendment No. 1 (2025), Federal Law No. 123-FZ.
