Tempered Safety Glass

California Glass Failure Analysis Expert discusses safety aspects of tempered glass:
The following codes interpret tempered glass for use as safety glass for the consumer:
Code of Federal Regulations (CFR) #16 Part 1201 1997, ANSI Z97.1-2004 and CAN/CGSB-12.1-M90 all discuss the safety aspects of tempered glass. All basically state that tempered glass is safer because it breaks into small pieces when broken by human contact. This is because the force of impact is perpendicular to the glass sheet. In contrast, annealed glass breaks into long, "blade like" shards that can injure a person impacting the glass. This safety aspect is very specific. However, it doesn't address the case of decorative glass hanging above the public. If this glass fails sponteneously (as in the case of nickel sulfide induced failure), it will fall in sheets that behave in a manner similar to a sheet of glass. This is because there sre no forces into this glass that will cause it to break into small cubes. Read Consulting reccomends that the public be protected from all decorative tempered glass.

What Is Safety Glass

Public Safety, Comments on the Nature of the Safety Glass Failure: There is a misconception that tempered glass is safe because it breaks into small cubes when it breaks. This is true if the glass is broken by impact from a direction perpendicular to the surface of the glass piece (i.e. someone walking into a window). This is not true of a suspended piece of tempered glass. If this glass fails due to NiS inclusions or for some other reason that does not include side impact, the glass can fall in large interlocking sheets. In this case, the tempered glass doe not perform safely. That is, someone walking under this piece of tempered glass can be seriously injured. Therefore, one should be cautious when selecting decorative glass hanging over public access areas. For these applications laminated glass is much safer.