Modern architecture has come up with a modern way to prioritise building safety through fire rated glass. Gone were the days where buildings were made of pure stone and steel. Instead, occupants of newer skyscrapers are now surrounded by natural light through glass walls. However, while fire rated glass usually plays a crucial role on this, different kinds of this special glass exist and the market, and they are not created equal. You might have come across different ratings like 30, 60 or even 120 minutes and wondered what exactly those numbers mean and why they matter.
Let’s break it all down in simple terms.
Fire rated glass defined
First things first, let us define what is fire rated glass.
Fire rated glass is a specially tested glazing material designed to resist the spread of fire, smoke and heat for a certain period. Unlike regular glass, it won’t immediately shatter under high heat or sudden temperature changes. Instead, it helps compartmentalise a fire, buying valuable time for evacuation and response.
So, when we talk about a glass panel being “fire rated for 60 minutes,” we’re referring to how long it can hold up under fire conditions while maintaining its integrity or performance based on its classification.
Now, let’s explore the key differences between the various ratings.
30-minute fire rated glass
Let’s start with the most basic level of protection: 30-minute fire rated glass. This is often considered “entry-level” in the world of fire rated glazing.
Glass rated for 30 minutes is usually designed to contain smoke and flame for short durations. It may not provide significant protection against heat transmission, which means while it stops fire and smoke, it doesn’t necessarily block the intense heat that comes with it. That makes it suitable for areas with low fire risk or as part of fire door assemblies where radiant heat protection isn’t required.
Because of its limited time rating, 30-minute glass is generally thinner, lighter, and easier to work with. It’s also more affordable compared to higher-rated options, making it a common choice for interior applications like corridor doors, transoms, and sidelites in commercial buildings.
But the key thing to remember? It offers basic containment, not full-scale heat resistance. So, it’s best used where code permits and where more robust protection isn’t essential.
60-minute fire rated glass
Jumping up to 60 minutes, we’re looking at glass that offers a much more serious level of protection. This glass is tested to withstand fire, smoke, and heat for a full hour.
A 60-minute rating generally means the glass can either:
- Stay intact and prevent the passage of flames and smoke for 60 minutes, or
- Do that and limit the transfer of radiant and conductive heat, depending on whether it’s classified as a fire-resistive or fire-protective product.
This brings us to an important nuance: fire-protective vs. fire-resistive. Fire-protective glass stops flames and smoke but may still allow heat to pass through. Fire-resistive glass, on the other hand, blocks all three—flames, smoke, and heat.
At the 60-minute mark, some fire rated glass products begin to fall into the fire-resistive category, especially if they’re multilayered or have intumescent interlayers that expand when exposed to heat. These are typically used in critical areas like stairwells, exit corridors, and certain occupancy separations.
So, with 60-minute glass, you’re getting more than just time. You’re also getting upgraded performance and peace of mind.
120-minute fire rated glass
And then we have the heavyweight: 120-minute fire rated glass. This is the most durable and fire-resistant glazing option currently used in commercial construction.
To qualify for a 2-hour fire rating, glass products undergo incredibly demanding testing. They must not only hold back fire and smoke for 120 minutes, but also resist thermal shock, radiant heat and hose stream tests with impressive consistency.
As you’d expect, this type of glass is highly engineered. You’re looking at multi-layer systems with specialized interlayers, multiple panes, and in some cases, insulating glass units (IGUs) that provide additional thermal performance.
The main difference here isn’t just the time, though that’s obviously significant. It’s the level of protection and resilience. A two-hour rated system is often used in areas that form part of the building’s core structural safety zones. Think fire exit enclosures, elevator shafts, and rated separation walls between large occupancy zones.
Not surprisingly, this glass tends to be the most expensive and requires precise installation by certified professionals. But the upside is unmatched fire resistance and full code compliance for high-risk, high-traffic environments.
The bottom line: It’s all about application and risk level
So how does all this translate into real-world choices?
While the minute ratings give a clear numerical difference, what really matters is the intended use of the space, the fire risk and the building code requirements.
- 30-minute glass is fine for low-risk areas and is typically used in doors or small windows.
- 60-minute glass begins to provide real fire-resistive capabilities and is suitable for corridors, stairwells and partition walls.
- 120-minute glass is reserved for areas where the most extreme fire exposure is anticipated and time is needed for safe evacuation or structural protection.
A quick word on code compliance
Fire rated glass isn’t a one size-fits all solution, and while understanding the rating system is helpful, building codes should always be your guiding reference.
Different jurisdictions may have different fire safety standards, and it is important to match the glass rating with the required fire resistance rating of the surrounding wall or door assembly. If the wall is rated for 2 hours, the glass installed in that wall also needs to meet the 2-hour standard.
Additionally, not all fire rated glass products are interchangeable. A 60-minute fire protective glass may not be approved for the same application as a 60-minute fire resistive one. Always check compatibility, ratings and certifications before making a final choice.
Get the glass with the right fire rating that suits your needs
Understanding the differences between 30, 60, and 120-minute fire rated glass isn’t just about knowing numbers, but about making smart, safe and code-compliant decisions for your building.
As the rating increases, so does the level of protection. It is not just in terms of time, but in how well the glass handles heat, pressure, and structural integrity during a fire.
Whether you’re an architect, contractor, or building owner, choosing the right fire-rated glass means balancing safety requirements, code compliance, aesthetics, and budget. But with the right knowledge, you can make confident decisions that protect both people and property.
If you’re unsure which rating is right for your project, it’s always worth speaking with a certified fire safety professional or glazing specialist. The right advice now can make a world of difference later.
Need help in choosing the right fire rated glass for your project? Feel free to reach out to VJF Systems. Our team is here to help guide you through your options and ensure your building stays safe, beautiful and code-compliant.