ASTM E84 determines the surface burning characteristics of building products and is one of the most common test methods used in the building industry. The test method measures relative burning behavior of materials by observing the flame spread and the smoke development compared against two control materials.

This standard is commonly used to test coatings, fire-retardant materials or treatments, foam plastics, interior finish materials, paints, and plastics. Like most fire test standards, the test method does not account for all the factors that are required for fire hazard or fire risk assessment of the materials, products, or assemblies under actual fire conditions.

Section 803.1.2 of the International Building Code (IBC) requires the flame spread and smoke development performance of interior wall and ceiling finish materials not to exceed certain thresholds when tested in accordance with ASTM E84 and other equivalent test methods. In addition to code compliance, many manufacturers use ASTM E84 as a quick, inexpensive test to measure limited fire performance as they develop new and innovative building product solutions.


Test Method

ASTM E84 steiner tunnel test flameASTM E84 is conducted on test specimens between 20 – 24 inches wide and 288 inches (24 feet) long with a typical maximum thickness of 4 inches. Some special Steiner Tunnels can be modified to accept test specimens greater than 4 inches thick, and the standard provides additional guidance about the effects of these modifications. Test specimens may be supplied in one continuous, unbroken length or in sections that will be laid adjacent to one another in the test tunnel.

Test specimens must be conditioned to a constant weight at a temperature of 73.4 °F ± 5 °F (23 °C ± 2.8 °C) with a relative humidity of 50 ± 5% before testing begins. The test specimens can be either ceiling mounted, or floor mounted in the test tunnel, depending on the design of the test tunnel. Regardless of the mounting method, the test begins when test specimens receive flame via two burners with a controlled airflow.

The test measures how fast and far the flames spread across the specimen’s surface and the amount of smoke developed throughout the test, typically through optical sensors. During the ten-minute test, a technician will monitor the specimen through the windows and perform real-time analysis of sensors in the test tunnel.


Test Results

While the two most commonly reported results from ASTM E84 are flame spread and smoke development, the standard provides several additional vital pieces of information, including:



  • Flame Spread Index (FSI)
  • Smoke Developed Index (SDI)
  • Time to ignition
  • Flame Spread Distance v. Time
  • Maximum Flame Spread Distance
  • Temperature v. Time
  • Time to Maximum Temperature
  • Smoke Area v. Time
ASTM E84 Steiner tunnel test

The FSI is a number that provides a comparative measure of flame spread derived from observations made during the progress of the boundary of a zone of flame under defined test conditions. The SDI is a number that provides a comparative measure of smoke development derived from smoke obscuration data collected during the test. Building Code officials and professional designers use the FSI and SDI to determine whether a product is suitable for its intended use.

Most commonly, both indices are used to determine the classification of a product in accordance with IBC Section 803.1.2; see table below. In the test report, FSI is rounded to the nearest multiple of 5, and SDI is rounded to the nearest multiple of 5 for values less than 200. SDI values that are greater than 200 are rounded to the nearest multiple of 50.

It is important to note that there is not necessarily a correlation between FSI and SDI values; products can spread flame quickly without generating much smoke and vice versa.

Flame Spread Index and Smoke Developed Index

ASTM E84 test results do not provide:

  • A measurement of heat transmission through the tested surface
  • The effect of the flame spread of an assembly on combustible walls and ceilings near the assembly
  • Classifying or defining a material as noncombustible
  • Evaluation of real-world fire conditions on a product, assembly, or surface


ASTM E84 is one of many common test standards used for code compliance of building products, especially interior finish materials. Manufacturers who want to avoid delays and extraneous testing for their product’s code compliance often work with an accredited third-party certification and testing agency. This is to identify all code compliance requirements before testing, which allows them to find partners who can fulfill all their needs.

Learn More about the Author: Mike Luna



ASTM E84-22. ASTM, 2022.
International Code Council. “International Building Code.” ICC, Accessed 08/16/2022.