Glazing is dangerous! Know your glass – Know the risks!

Glazing is dangerous! Know your glass – Know the risks!

Lethal injuries can be caused by broken glazing. Survivors are commonly scarred for life, and frequently disabled. Such injuries are unnecessary, and can be largely avoided by the use of appropriate glass in risk situations. This is the reason for the Regulations that govern glass installation and our business when it comes to glass replacement.

There are only two true safety Glasses (Toughened and Laminated) but other glasses can, in certain circumstances, form part of safety solutions. BS 6206:1981 This is the key British Standard for Safety Glazing classification, after the United States' ANSI Z 97.1-1975.
BS 6206 specifies impact tests that simulate the mass of a running child. A 1001b (45.36 kg) leather punch bag (impactor case) filled with lead shot is swung against a framed glass test panel from three different drop heights (1219mm, 457mm & 305mm). If the glass does not break (or breaks "safely" according to carefully specified criteria on the size and shape of the broken pieces) the sample is classified A, B or C. "A" is the highest grade, surviving all three drop heights. Plastics glazing can be tested to the same Safety Glazing classifications.

We have detailed below the various types of glass used throughout Britain’s buildings. It’s important to know the glazing housed within your building. If you’re unsure then Glazing Refurbishment Limited has the capability to fully inspect your site, provide detailed reports on your glazing and importantly carry out any required works deemed necessary

ANNEALED GLASS
Often referred to as "ordinary" glass, this is the standard glazing product, and also the basic material for Safety Glasses. Glass is a "supercooled liquid" and one of the most robust materials used in Building - if unbroken it can perform for hundreds of years. Glass is manufactured from silica sand (72%), soda (l4%), lime (10%), and various oxides (4%), fused in a furnace at around 1500°C then (in the most frequently used process) flowed continuously onto molten tin where it solidifies. No polishing is required. Annealed glass can also be one of the most dangerous materials used in Building. When broken it forms sharp glass "daggers" which cause serious injuries. Annealed Glass should therefore only be used in low-risk situations (usually the largest percentage of glazed areas).

TOUGHENED GLASS
This is a true Safety Glass to BS 6206. It begins as ordinary annealed glass, is cut to the exact finished size, uniformly heated to 700+ °C then cooled rapidly by blowing air on both sides. The outer surfaces cool faster than the core, and permanent stresses are built up. After toughening, the glass can have up to 5 times its original strength. Toughened glass breaks into small blunt fragments, reducing the risk of serious injury. Typically when broken the whole pane crazes and falls out in pieces. Toughened glass products cannot be cut, drilled or shaped - all such work must be completed before toughening is carried out. Toughened glass can be identified by its edge bevels introduced during preparation to avoid localised stress cracking, characteristic "leopard spots" seen in certain lighting conditions, and a manufacturer's stamp in the corner stating its BS 6206 grade. Various scientific identification techniques use polarised and ultra-violet light sources, or a laboratory Differential Surface Refractometer can compare optical distortions between the "fringes" occurring during toughening. Toughened Glass usually falls out of its frame when broken, and fragments can cause injury and shock if falling from some height. Additional containment is therefore needed in (for example) roofing installations. Toughened Glass is subject to spontaneous fracture, sometimes by the gradual expansion of a Nickel Sulphide inclusion, or perhaps by minor damage of an edge. Thermal movements of frames, or near-invisible accidental damage during installation, can lead to such sudden failures. Improvements in manufacturing processes, particularly the technique of Heat Soaking (Heat Soaked Toughened Glass) have meant that Nickel Sulphide inclusions have been less common in recent years, however the problem is not eradicated and must still be considered a significant risk.

LAMINATED GLASS
This is a true Safety Glass to BS 6206. It begins as two or more sheets of ordinary annealed glass bonded together, with interlayer(s) of polyvinyl butryl (PVB). Laminated glass's strength differs little from that of the original glass from which it is fabricated, but the PVB interlayer absorbs and distributes impact energy, giving valuable resistance. When broken, cracking is typically limited to the area of impact, the remainder of the pane remaining clear and (mostly) in place. Laminated glass often has no markings - these can be lost when cutting from larger sheets, however it must be given BS 6206 markings if is to qualify as a Safety Glass. Laminated glass can be identified in situ using specialist ultra-sound or laser intruments, or visually by dismantling and inspecting an edge, where the PVB interlayer(s) can be seen. Laminated Glass offers considerable protection against people or objects falling through.

HEAT STRENGTHENED GLASS
This is NOT a Safety Glass, and its name can cause some confusion. It is a heat-treated Annealed Glass (as is Toughened Glass) and can achieve twice the original mechanical strength, which can be useful, but it does not set out to achieve a BS 6206 Safety Glass classification.

WIRED GLASS
Old-style Wired Glass (known as Georgian Wired Glass) is NOT a true Safety Glass to BS 6206. Although sometimes safer than plain annealed glass, it should not be used in risk situations unless further protected. Wired glass is a rolled Annealed Glass containing 12.5mm steel mesh that does not contribute to its strength (the wires actually introduce planes of weakness) but helps contain broken pieces. It offers more security than non-wired annealed glass, as it is relatively difficult to penetrate the mesh. It also offers more fire-resistance than clear Annealed Glass, and often provides an inexpensive solution in this area. Wired Glass has several appropriate uses but its visual appearance may not be acceptable to some specifiers who often prefer a fully clear (more expensive) option for aesthetic reasons. A Wired Safety Glass has become available in recent years - a true BS6206 Safety Glass - gaining strength from a thicker wire.

PLASTICS GLAZING PRODUCTS
A number of plastics (eg polycarbonates) can achieve the true Safety Glass criteria of BS 6206. None have the durability of glass (in particular they are subject to abrasion, discoloration etc), but improvements are coming along all the time. Plastics films may be applied to Annealed glass to achieve Safety classifications, and several useful products are available. They each suffer durability limitations, but can be of great value in the short term (eg as an interim solution ahead of a building alteration). Plastics glazing has a useful role in Safety applications, and will certainly become more predominant in the future.

Have a think about the type of glass your building houses.

Does it comply with the above legislation?

Have you had a close call in the past?

When was the last time you had your glazing inspected?

If the answer to any of the above is no then please call us here at Glazing Refurbishment Limited.
Swift response is guaranteed, surveys carried out and reports provided instantly. You as the building owner must show due diligence in providing your employees, customers, pupils and tenants a safe working environment. Glazing Refurbishment is here to ensure that happens