DOT "safety" glass - warning

[Inspector Gadget]

Our office has seen a rather alarming influx of people using DOT-rated safety glass in such things as residential guards on decks. Below is an image found in the exit door of a Part 3 building under construction. In all cases, the installer/distributor has stated "you're the first one to complain about such things," which might be smoke in the colon ....

BUT it's worth raising for discussion.



I also, earlier this year, had an issue with a glass-filled residential door from (IIRC) Belgium that had Euro markings. In that case, the manufacturer was able to state that the glass also met ANSI Z97.

EDIT: Part 3 reference is 3.3.1.19(7) which refers to 9.6.1.4

 

[arwat23]

This seems like it's just cheaper Chinese (automotive) glass that probably meets the standards set out by building code. If it's considered safe for a car, it's (probably) safe for a residential door or guard.

Edit: But I'd still force the installer / supplier to prove it meets what's specifically called out for in code.

 

[Inspector Gadget]

This seems like it's just cheaper Chinese (automotive) glass that probably meets the standards set out by building code. If it's considered safe for a car, it's (probably) safe for a residential door or guard.

Edit: But I'd still force the installer / supplier to prove it meets what's specifically called out for in code.

The tests for DOT glass and ANSI Z97.1 glass are *entirely* different.

DOT glass is tested with a small object dropped from a large height; ANSI Z97 glass is a large object dropped from a small height. Totally different tests.

And I'm not going to put my career at risk by approving something that may not, in fact, be suitable for the job.

 

[arwat23]

The tests for DOT glass and ANSI Z97.1 glass are *entirely* different.

DOT glass is tested with a small object dropped from a large height; ANSI Z97 glass is a large object dropped from a small height. Totally different tests.

And I'm not going to put my career at risk by approving something that may not, in fact, be suitable for the job.

Yeah, I know (well, assumed) they were different. And like I said, I wouldn't approve it either. But I'm willing to bet that it can pass the tests it's suppose to test to because a car is subject to a lot of stress (and the glass, assuming it's windshield glass serves a structural component in vehicles too). They just need to show me that it can, otherwise they're going to have to replace it.

I wonder how much the savings are using this glass over the glass they should be using...

 

[tmurray]

Ask them what jurisdictions have accepted this glass and call them to ask how they did it.

Either you will get a good answer on how to proceed with your situation, or the other person might get a heads-up that they are missing something in their inspections.

As a funny storey, I was looking at an alternative solution for another jurisdiction and the professional indicated that the product had been used for an identical application already in that jurisdiction. However, the building department was able to confirm that the product had in fact not been used. The quality of the remainder of the alternative solution was at about the same level.

 

[Sifu]

Opportunity for a photo from my archive: I have written on the forum about it before. Contractor INSISTED it was tempered. I said no marking=no safety glazing. A label showed up. So did a hammer. Give him SOME credit though, he put scotch tape over the label maker sticker for a little added credibility. Just can't make this shlt up.

 

[Joe.B]

Opportunity for a photo from my archive: I have written on the forum about it before. Contractor INSISTED it was tempered. I said no marking=no safety glazing. A label showed up. So did a hammer. Give him SOME credit though, he put scotch tape over the label maker sticker for a little added credibility. Just can't make this shlt up.
View attachment 17014

Somebody used a hammer to prove it wasn't tempered glass? That's hilarious. It would have been even more hilarious if it actually was tempered...

 

[e hilton]

Somebody used a hammer to prove it wasn't tempered glass? That's hilarious. It would have been even more hilarious if it actually was tempered...

As long as you don’t strike an edge, a smooth faced hammer isn’t going to pop the glass. Hit it 3-4 times and call it good.

 

[ICE]

Here's the label from above, rotated.

 

[Sifu]

Somebody used a hammer to prove it wasn't tempered glass? That's hilarious. It would have been even more hilarious if it actually was tempered...

Owner got mad enough at the contractor after a few months of excuses and lies he invited me over after the new windows were finally installed to witness it. I never said it wasn't safety glazing, hair splitting to be sure but I was careful to say only that it wasn't marked as safety glazing, but still a little afraid of the egg on my face it it was safety glazing. I'm sure I would have been fired if that were the case. I had done my homework though, even spoke directly to the manufacturer of the individual glass panes. He said that while he couldn't guarantee a pane or two doesn't slip through the cracks, internally they absolutely do not consider it safety glazing unless it is etched. As the MFR they backed me 100%.

 

[ICE]

2403.1 Identification. Each pane shall bear the manufacturer’s mark designating the type and thickness of the glass or glazing material. The identification shall not be omitted unless approved and an affidavit is furnished by the glazing contractor certifying that each light is glazed in accordance with approved construction documents that comply with the provisions of this chapter. Safety glazing shall be identified in accordance with Section 2406.3.

Each pane of tempered glass, except tempered spandrel glass, shall be permanently identified by the manufacturer.The identification mark shall be acid etched, sand blasted,ceramic fired, laser etched, embossed or of a type that, once applied, cannot be removed without being destroyed.


Tempered spandrel glass shall be provided with a removable paper marking by the manufacturer.

2406.3 Identification of safety glazing. Except as indicated in Section 2406.3.1, each pane of safety glazing installed in hazardous locations shall be identified by a manufacturer’s designation specifying who applied the designation, the manufacturer or installer and the safety glazing standard with which it complies, as well as the information specified in Section 2403.1. The designation shall be acid etched, sandblasted, ceramic fired, laser etched, embossed or of a type that once applied, cannot be removed without being destroyed. A label meeting the requirements of this section shall be permitted in lieu of the manufacturer’s designation.


Exceptions:
1. For other than tempered glass, manufacturer’s designations are not required, provided that the building official approves the use of a certificate, affidavit or other evidence confirming compliance with this code.
2. Tempered spandrel glass is permitted to be identified by the manufacturer with a removable paper designation.

 

[Sifu]

A label meeting the requirements of this section shall be permitted in lieu of the manufacturer’s designation.

This sentence has been a source of debate. Some say a label can be permitted but only for the manufacturer, not the safety glazing. Some say the label can be permitted in lieu of all the information. The exception says the manufacturers designation can be omitted if not "tempered" which is one type of safety glazing. So if it is tempered, it must be designated as such on the glazing which would seem to nullify the sentence when tempered is the claim.

In the case illustrated with my picture, they claimed tempered, it was clearly not any other type so I felt pretty good with the backing of the manufacturer.

I worked at a large AHJ some years ago. They had a policy that allowed shower glass without etching as long as a letter was submitted promising it was. I pointed out the exception. They changed the policy.

I have had conversations with several glass manufacturer's. They all have said we etch, and if we don't, it's not tempered, whether it actually is or isn't because there is no good, reliable way to tell after the process (unless you use a hammer?)

I looked a t a job for a contractor friend doing a remodel (not inspected, just advised) a few weeks ago. The owner wanted to re-use the shower door after a remodel. I found the etching, and educated the contractor about the importance of finding it. There was also a separate site constructed window in the shower overlooking the tub. It had no etching, but was laminated. In that case, it is possible a letter could have been accepted when originally installed. The fact that it was laminated, and I can almost guarantee it was not something any inspector ever looked at, I assume the original installer knew at least enough to have put in laminated glazing for a reason, rather than a simple non safety glazed single pane. So good on them.

 

[ICE]

there is no good, reliable way to tell after the process

Tempered glass (also known as toughened glass) is heat-treated for strength and safety, shattering into small, blunt pieces rather than sharp shards. Identifying it is crucial for applications like windows, doors, or screens to ensure compliance and safety. While visual inspections (like checking for etched stamps or rounded edges) are common, they aren't always reliable or accessible. Below are effective device-based methods, ranging from simple household tools to professional equipment.1. Polarized Sunglasses or Lens Viewer (Most Accessible Device)

• How it works: Tempered glass creates strain patterns during manufacturing, visible as colorful streaks, dark spots, or a rainbow-like interference under polarized light. Hold polarized sunglasses (or a polarized lens) against the glass while viewing it in bright light or against a reflective surface like a phone screen (turned off). Tempered glass will show distinct lines or distortions; regular glass appears uniform.
• Why it's effective: This leverages photoelasticity to detect internal stresses unique to tempered glass.
• Pros: Inexpensive (sunglasses cost ~$10–20); non-destructive.
• Cons: May not work well on very thick glass or in low light.
• Example use: Test car side windows (usually tempered) as a reference.

2. Ultraviolet (UV) Light Source (For Fluorescence Testing)

• How it works: Shine a UV blacklight on the glass in a dark room. Tempered glass often fluoresces with a more even, greenish pattern due to manufacturing impurities, while annealed (non-tempered) glass shows uneven or no glow.
• Why it's effective: Highlights subtle chemical differences from the tempering process.
• Pros: Quick for batch testing large sheets; portable UV flashlights cost ~$5–15.
• Cons: Requires darkness; not 100% conclusive without lab follow-up.
• Example use: Inspect architectural glass panels or shower doors.

3. Strengthened Glass Detector (Professional Handheld Device)

• How it works: Devices like the GT975 Strengthened Glass Detector use laser or optical scanning to measure stress levels or thickness from one side, confirming if glass is tempered (or laminated). It can test single or multi-pane windows and even identify the first layer's thickness.
• Why it's effective: Provides quantitative data on compressive stress, a hallmark of tempering.
• Pros: Accurate for installed glass; non-invasive.
• Cons: Specialized tool (~$200–500); typically used by installers or inspectors.
• Example use: Window film applicators or building inspectors verify compliance.

Tempered glass is still a major hazard. When a window shatters, there is a border of jagged glass that is trapped in the gasket.

 

[Sifu]

I specifically asked about the glasses, even used a pair on known tempered glazing. As I recall some were obviously different than others, even though they were etched as tempered. Glass MFR said he doesn't recommend relying on them. This was 15 years ago, so maybe they have something now he could rely on, but back then he was pretty clear. No etch = no temper, and forget about the liability and reliability of other methods.

I couldn't take the time to pull a sash, take it to a dark room and use a UV light on it, so that was about too. And, since I was on pretty thin ice with the CBO for even bringing the issue to light (punny!), I'm pretty sure asking for a professional hand-held device was a no-go.

Simple in my eyes. Why bother and assume any liability? Etch it.

 

[ICE]

Etch it

I've known about the other methods for years and it is always been, Etch it.

 

[ICE]

This sentence has been a source of debate. Some say a label can be permitted but only for the manufacturer, not the safety glazing. Some say the label can be permitted in lieu of all the information. The exception says the manufacturers designation can be omitted if not "tempered" which is one type of safety glazing. So if it is tempered, it must be designated as such on the glazing which would seem to nullify the sentence when tempered is the claim.

2406.3 Identification of safety glazing. Except as indicated in Section 2406.3.1, each pane of safety glazing installed in hazardous locations shall be identified by a manufacturer’s designation specifying who applied the designation, the manufacturer or installer and the safety glazing standard with which it complies, as well as the information specified in Section 2403.1. The designation shall be acid etched, sandblasted, ceramic fired, laser etched, embossed or of a type that once applied, cannot be removed without being destroyed. A label meeting the requirements of this section shall be permitted in lieu of the manufacturer’s designation.

The indication is that a paper label can be affixed to the glass that identifies the glass as tempered as long as the label can't be removed without destroying the label. I have never seen such a label and only once has a contractor attempted to convince me that there was a label that was inadvertently removed before I saw it. As I recall, he came up with paper labels that said "TEMPERED". It was comical as they were peeling away from the glass.