Exploding glass is a term growing in popularity with consumer affairs reporters. The spontaneous, sometimes random, shattering of tempered glass in doors, showers and other consumer glass products, such as tables, has generated lots of news and complaints to the United States Consumer Product Safety Commission. It is also the subject of recent lawsuits alleging injuries as a result of breakage. While it can seem as strong as steel and safe in most applications, installations involving the use of tempered glass must consider the product’s characteristics and potential for a spontaneous failure in contract and workmanship.
The use of tempered glass is generally a function of safety. IBC and IRC requirements for safety glazing are often met through the use of tempered glass that complies with ANSI Z97.1 and 12 CFR 1201. The tempering process quickly cools the outer surfaces of a glass panel so the middle remains in an unset state. This makes the pane “safer” because it is stronger and less likely to form the large shards that annealed glass does when broken.
The tempering process also leaves the pane under substantial surface compression as the core tries to pull the cooled surfaces together. ASTM C 1048, the Standard Specification for Heat Strengthened and Fully Tempered Glass, requires at least 10,000 psi of surface compression for fully tempered glass. So, while the compression is what gives tempered glass its strength, reliance and breakage characteristics, it is also what can lead to the phenomenon called exploding glass.
Whether caused by imperfections in the glass, installation or abuse, the high compression of tempered glass itself means that its failure is swift and sudden. And where not surrounded by a supporting frame, the breakage can also be dangerous. Tempered glass may break into small pieces, but those pieces are still sharp and pose a risk of bodily injury.
Where an installation calls for the use of tempered glass, glazing contractors must not forget the risks and benefits that come with its physical properties. The potential for harm posed by tempered glass failure presents risk management and legal exposure potentials that are often overlooked. But there are some steps that can help.
1. Know safety glazing options.
Tempered glass is exceptionally useful, but may not be the only safety glazing option available for an installation. Proactive risk management can include documenting a review of various safety glazing materials. Do not avoid considering laminated glass because of the cost.
When a project requires safety glazing, and tempered glass is the choice, look to the area surrounding the installation for potential stresses or breakage points that could be eliminated or mitigated before work gets underway. Identify these issues for the architect or builder, and confirm authorization to proceed.
2. Ensure that tempered glass is properly sourced.
Look for the etching of compliance with ANSI Z97.1 and 12 CFR 1201. The mark is a safety requirement in many instances and ensuring it is present is a good job checklist item.
3. Disclose where tempered glass is used.
Architects and contractors often know where safety glass is required, but proactive disclosure of the use and location of tempered glass on a project can be useful for an owner. Moreover, advising of the potential for occlusions or other microscopic imperfections can help ensure diligence and inspections continue after job completion.
4. Use quality fixtures and equipment when fabricating and installing tempered glass.
Improper fabrication equipment could harm the overall strength of the pane. Improper size, placement or installation of hardware can place a tempered glass pane under stresses that can contribute to its failure. Where appropriate, offer hardware alternatives that account for tempered glass if concerns exist regarding the specifications.
5. Quality check the workmanship during and after installation.
Proper fabrication and handling of tempered glass can help limit the potential for breakage. Documenting those steps can help limit legal risk and exposure.
6. Ensure jobs are protected.
Failures of tempered glass can come years after installations are complete. Today’s insurance policy may be a source of legal defense and protection that is looked to 10 years from now. Check your policies and coverage to ensure ongoing protection for completed operations.
The use of tempered glass should account for its physical properties and the risk of potential failure. Glazing contractors are viewed as glass experts that are expected to know the risks posed by glazing options, and ways to proactively address those risks. That requires education. It also means staying current with glazing industry information. The National Glass Association and GlassBuild America are good places to start.
