Accurate fire testing of PFP coatings ensures structural safety

Published 22 July 2025

With building codes evolving and demand rising for fire-resilient infrastructure, a market leader with PPG Protective and Marine Coatings explores the critical role of accurate fire testing for cellulosic passive fire protection (PFP) coatings. These PFP coatings are used frequently on structural steel assets.

Steel remains the backbone of modern infrastructure. It enables architects and engineers to quickly construct large and robust structures, ranging from sports arenas and airports to high-rises and advanced manufacturing plants. But if fire hits, strength alone won’t cut it.

According to the American Institute of Steel Construction, structural steel typically loses about 50% of its load-bearing capacity at temperatures around 1,100°F (593°C), depending on load conditions and design factors. Cellulosic fires — fueled by common materials like wood, textiles, and paper — can reach these temperatures within minutes.

To safeguard structural integrity during a fire, building codes require the use of passive fire protection (PFP) systems. Among the most effective solutions are intumescent coatings, which are protective layers applied to structural steel. These coatings provide critical fire resistance while allowing architectural design flexibility. With efficient application methods and fast dry times, the use of intumescent coatings in infrastructure projects is growing.

When exposed to high temperatures, intumescent coatings chemically react, expanding to form a stable, insulating char. This char significantly reduces heat transfer to the steel, helping maintain its load-bearing capacity for a specified period — critical for allowing evacuation and firefighting efforts. However, for this system to work as intended, contractors and specifiers must understand a crucial component. That component is accurate fire testing.

Choosing the Right Coating Protects More Than Steel

Fire protection coatings do more than preserve steel structures — they also safeguard lives, property, and operational continuity. When contractors, engineers, and specifiers select coating systems that are properly tested and aligned with real-world conditions, they help mitigate fire risks, minimize downtime, and protect investments.

In fact, reliable intumescent systems can help maintain structural integrity during fire events, providing first responders with more time to evacuate building occupants.

Project teams can enhance confidence in the construction process by specifying coatings that have undergone rigorous, standardized fire testing. This approach reduces project uncertainty, avoids costly rework, and ensures the structure meets performance expectations under fire conditions.

Moreover, investing in fully tested and certified passive fire protection systems streamlines project execution and delivery. With validated documentation, proven system compatibility, and compliance with regional fire codes, teams can avoid delays and facilitate coordination among stakeholders — such as engineers, fabricators, contractors, and inspectors.

Fire Testing Must Reflect Real-World Conditions Effective fire testing must reflect the actual construction assemblies, steel profiles, load conditions, and environmental factors. It should also consider:

• Correct dry film thickness (DFT) based on the required fire rating;

• Compatibility of primers and topcoats with the intumescent layer;

• Performance under both restrained and unrestrained structural conditions.

When coatings perform as tested, structures remain stronger and construction schedules remain on track.

Know the Standards

PFP coatings do not have a universal standard. They must pass the right fire test for the region where the project will be built. Examples include:

• UL 263 and ASTM E119, North America

• EN 13381-8, European Union and United Kingdom

• GB 14907, China

These standards follow a “cellulosic fire curve,” which simulates fire growth driven by typical building contents. While the general curve is similar globally, each standard defines unique parameters, including furnace conditions, failure criteria, temperature thresholds, and test durations. For example, a coating qualified under EN 13381-8 does not automatically meet the requirements of UL 263 in North America

Contractors, engineers, and specifiers must verify that the selected fire protection system meets both the building code and the applicable test standard for the project location.

Key Testing Insights for Fire Protection Systems

It’s vital to test the full system, and not just the intumescent layer.

Every layer of the system — from primer to topcoat — must support the expansion and adhesion of the intumescent layer. If the primer causes delamination or if the topcoat interferes with char expansion, the entire system performance can be compromised.

Load Matters

Higher structural loads can increase risks of deformation and cracks during fire exposure. Fire tests must reflect the actual assembly design and load conditions, consistent with structural codes such as those established by the American Society of Civil Engineers (ASCE).

Certification Is Mandatory

Always confirm independent third-party certification. Look for accreditations from bodies like Underwriters Laboratories (UL), Factory Mutual (FM) approvals, or equivalent agencies. Request product data sheets (PDS), fire test listing reports, and test results relevant to your region and application.

Check the Build-Up

Don’t apply beam data to a floor assembly or assume that an untested configuration will work. Confirm that the tested system matches the exact steel profile, assembly type, and environmental conditions of your project.

What Are the Proven Field Results?

At the Chongqing Jiangbei International Airport’s T3B Terminal — the world’s largest satellite terminal — accurate fire testing played a critical role in the selection and validation of passive fire protection systems.

Faced with ambitious design, fire resistance requirements of up to three hours for steel components, such as shuttle and conical-shaped concrete-filled columns, project teams applied intumescent coatings as part of a multilayered protection system. These systems were rigorously tested not only for temperature performance but also for real-world mechanical stress, weld variability and coating compatibility under GB 51249-2017 fire safety standards.

On this project, PPG’s STEELGUAR® FM550 system was selected for its proven ability to meet structural and aesthetic goals, with performance verified through third-party assessments and year-long testing cycles. By aligning fire testing protocols with project specifics, such as structural loads and material combinations, the team can drive better outcomes and ensure fire protection systems perform effectively when it matters most.

Key Takeaways for Contractors, Engineers, Specifiers

When evaluating structural steel intumescent coatings, don’t rely on performance claims alone.

Ask about the test standards, verify third-party certifications, and confirm that the system includes tested primers and topcoats.

Most importantly, ensure the test conditions match how the product will be used on-site. Fire protection coatings properly tested and specified reduce risks of failure, minimize rework, and provide long-term cost benefits while maintaining structural integrity that can ultimately provide more time to safely evacuate building occupants.

Fernanda Gregati is the business development manager for PPG’s protective and marine coatings business. She is a seasoned chemical engineer and business development leader with solid experience in passive fire protection and protective coatings.

Originally published in Coatings Pro.