Fire Rating Classifications Explained

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Fire rating classifications for your industrial or commercial project can be tricky. If you’re starting a new building project, you should make sure that you have the right covering. Below, we’ll discuss fire rating classifications from the American Society for Testing and Material (ASTM). We’ll also go over how to ensure your project meets the current standards.

What are the different fire rating classes?

There are two main fire rating tests — the ASTM E-84 and the ASTM E-119. Each test measures distinct aspects of fireproofing burn behavior.

The ASTM E-84 tests characteristics of flame and smoke of a material. The ASTM E-119 measures the fire resistance of a structure. With the right covering, your project can exceed the requirements for both tests.

We’ll go over the details of each of these tests below. We’ll also discuss why we think you should try FlameOFF’s Fire Barrier Paint for your project. Read on to learn more about how to protect your project.

What are ASTM E-84 flame spread ratings?

The ASTM E-84 is based on two main metrics of burning behavior. These metrics are flame spread and smoke development. The flame spread index is a measure of how quickly the flame travels after the fire is initiated. The smoke development rating tells you how much smoke is produced over a period of time.

Flame spread index and smoke development are tested in the Steiner Tunnel, a 24 x 24-inch steel box. A sample of the material is exposed to two burners. Then, the sample is monitored through a window. The flame spread and smoke development are analyzed with specialized software.

These metrics are rated in three different classes. We’ll go over these below.

What is a Class A fire rating?

Class A (or Class 1) is the best fire rating. The flame spread for a Class A fire rating is 25 or lower, and the smoke development does not exceed a maximum of 450. Many facilities require a Class A rating for building materials. For example, hospitals typically require Class A ratings.

If you need a Class A fire rated paint, look no further than FlameOFF’s Fire Barrier Paint!

FlameOFF’s Fire Barrier Paint is ASTM E-84 compliant, has a Class A fire rating, and is ASTM E-119 compliant, meaning it can provide 1- and 2-hour protection based on the substrate you’re painting.

What is a Class B fire rating?

For a Class B fire rating, the minimum flame spread is 26, and the maximum is 75. The smoke development must not surpass 450 to qualify as a Class B fire rating.

What is a Class C fire rating?

For a Class C fire rating, the flame spread is between 76 and 200. Like Class B and Class A, the maximum smoke development is 450.

What are ASTM E-119 fire ratings?

The ASTM E-119 is a time-based fire test. It gives an assessment of the fire resistance and integrity of a structure.

To perform the ASTM E-119 test, a sample of a material is placed in a furnace. The material is left in the furnace for a pre-specified amount of time and temperature. At the end of the test, the material is checked for its structural integrity.

Fire ratings for the ASTM E-119 typically fall between 1 to 4 hours. Longer times indicate better fire resistance.

What fire rating you need will depend on your construction type (1 through 5), whether the substrate you’re painting is on the interior or exterior of your building, and whether or not the structure is load bearing. LSU provides a useful fire resistance requirement chart for laboratories that helps illustrate this point, but you’ll need to speak with a coatings professional to identify exactly what specifications are needed for your project.

Flame spread rating by material

Different materials have higher and lower flame spread rating. The chart below compiles information from various sources and shows flame-spread ratings for some common building materials according to the Louisiana Fire Marshal website:

Note how treating plywood with a fire resistant paint or spray can improve its flame spread rating from a Class III to Class I.

What is a 1-hour fire rated wall?

A 1-hour fire rated wall is able to remain intact after one hour of being exposed to fire. For example, the fire would not penetrate the structure after an hour. If your project keeps its integrity for at least one hour of burning, it would receive a 1-hour rating. Most facilities require a minimum of a 1-hour fire rating.

If it could withstand longer than an hour of burning, the rating would reflect the length of time that it holds up. For example, a material with a 2-hour fire rating can withstand fire for two hours.

There are several materials that are designed to be fire resistant. We’ll go through some of these below.

• Concrete: With low thermal conductivity, it takes more time for a fire to take effect in concrete. It is also non-combustible, which makes concrete good fire-resistant material.
• Stucco: Most stucco is made with cement and is reinforced with metal mesh. An inch of stucco easily receives a 1-hour fire rating.
• Brick: Thick structures made of brick normally achieve a 1-hour fire rating. Mortar is not as fire resistant as brick, but brick is still one of the best materials for fire resistance.
• Gypsum (or drywall): One of the most commonly used fire-resistant materials is gypsum. Gypsum includes a non-combustible core. It is made with chemically combined water in the form of calcium sulfate. Water is released when gypsum is affected by fire, which blocks heat transfer.

Some walls are built with materials that come guaranteed with a 1-hour fire rating. For example, the Intertek Design LPB/WPPS-60-01 wall is constructed with gypsum. It is designed to receive 1-hour fire ratings for both sides of the assembly.

How do you improve your fire rating?

You can improve your fire rating by using the right covering. With FlameOFF’s Fire Barrier Paint, your project will easily exceed standards for both the ASTM E-84 and ASTM E-119 tests.

Specifically, FlameOFF’s Fire Barrier Paint is compliant with ASTM E-119 ratings of 1 to 2 hours of fire endurance. It is also compliant with ASTM E-84 test Class A fire ratings on most materials.

Try FlameOFF’s Fire Barrier Paint to make sure that your project is well protected.

This article was last updated on September 23rd, 2023 with the latest information about fire rating classifications.