When specifying architectural glazing, the impact resistance of glass is an important factor to consider
There are many ways to increase the impact resistance of glass from using toughened glass to using laminated glass. This looks at both the impact it takes for the glass to break and the way in which it breaks. This technical advice article will outline some of the ways in which the impact resistance of glass is tested and the classifications it can achieve.
Safety Standard for Glass
Glazing materials that are specifically made for use as safety glazing materials (in certain building locations where human impact can occur) should be classified according to their performance. BS EN 12600 has now replaced BS 6206 as a European-wide performance standard for the impact resistance of glass.
The BS 6206 standard involves a series of tests where a lead-filled leather bag weighing 45kg is dropped like a pendulum from different heights onto the glass. The BS EN 12600 standard has been designed as a more up to date test although the performance levels are almost the same. Similarly, the EN 12600 test involves a weight being dropped at three different heights, 190mm, 250mm and 1200mm. This weight will be dropped onto a standardly sized pane of glass, the classifications of the impact resistance of glass then depend on at which point the glass breaks.
Safety Standard for Glass
Classifications within BS EN 12600, starting with the highest performance are:
- Class 1B1
- Class 2B2
- Class 3B3
The safety classifications for BS 6206 are only slightly different:
- Class A
- Class B
- Class C
In order for glass to be classified as an impact-safe material, the glass must undergo the Safety Standard Test. This test is used to define the level at which glass will 'break safely', meaning there will be no large shards of glass, only small fragments that will not cause as much injury.
BS EN 12600 Classifications
When testing the impact resistance of glass using the EN 12600 classifications, class 1 is used for testing the glass for critical applications with the drop height of 1200mm. Class 2 is used as an equivalent to more than an adult walking into the glass but less than if the adult were to force their way through by running at it. The drop height for this classification is 450mm. The last classification, class 3 is equivalent to an adult pushing firmly against the glass or a child running into it, the drop height for this class is 190mm.
All three classifications have a type B breakage which is shown by the fragments being held together, this is the typical breakage mode for glazing products such as laminated glass or glass where a safety film has been applied.
Classified materials that are used as safety materials and meet the performance criteria of BSEN 12600 must carry a recognisable mark to show the level of safety achieved during the testing process.
Toughened safety glass should always obtain a Class 1B1 classification, making it one of the safest glazing products in terms of the impact resistance of glass. Laminated safety glass with a PVB interlayer normally achieves a Class 2B2 classification dependent on the glass and interlayer thickness. Wired glass will obtain a Class 3B3 classification.
These standards were put in place to reduce the risk of injuries such as cutting or piercing of glass if it were to break. They are also in place to maintain the containment characteristics of the glass.