Welcome to our celebration and remembrance of UL’s rich contribution in fire safety testing, with a direct focus on the reaction to fire characteristics of building materials and systems.

How it All Started


In 1894,William Henry Merrill, an electrical engineer, founded Underwriters Laboratories (now known as UL). As an electrical inspector for the Chicago World’s Fair, he was hired to examine the electrical safety of the Colombian Exposition’s Palace of Electricity. This was one of the first instances where electricity was used on such a large-scale for illumination. The proliferation of untamed DC circuits and the new, higher voltage AC currents caused a great deal of concern and a rash of fires. Merrill wanted to understand the hazards posed by this new technology – and a new independent testing laboratory was born. Interestingly, while Merrill’s background and his first challenge were electrical, the first UL Standard Tin Clad Fire Doors (1903). Merrill and his colleagues understood the great importance of passive fire protection to the overall safety of buildings.

Passive Fire Protection & Reaction to Fire Characteristics

From then until now, the primary fire safety objective has remained consistent – prevent the fire from occurring or manage the fire impact. Two well-known approaches for managing the impact of a fire are passive or active fire protection.

Passive Fire Protection can be defined as the implementation of products and systems that do not require any external power but rather rely on construction features that either limit the rate of fire growth or compartmentalize a building fire to a limited area. Active Fire Protection, on the other hand, is the implementation of systems and products that require some amount of action or motion, such as manual, mechanical, or electrical power, in order to work efficiently in the event of a fire. Examples of active fire protection include detection systems, sprinklers, fire suppression systems, pumps, and extinguishers.

Compartmentalizing a building is done by using fire-resistance rated walls and floors, fire doors, dampers, and resistant penetration through room boundaries. Rate of fire growth is controlled by selecting materials that limit their contribution to the fire to which they are exposed. These products slow the fire growth, thereby giving additional time for safe egress and in some cases reducing property damage. To determine the reaction to fire of materials, UL measures characteristics such as time to ignition, surface flame spread, fire growth, peak or average heat release, and smoke contribution. Frequently tested building materials include interior finish materials, room contents, roofing materials, and exterior wall materials.

The chart below demonstrates a typical fire scenario and the responses through either passive or active products or systems.
Please look for future articles throughout 2016. The topics include key areas where UL has led the advancement of scientific research and testing the Reaction to Fire characteristics of building materials and systems. These include Surface Burning Characteristics (UL 723 / ASTM E84), Air Ventilation Products (UL 181), Roofing (UL 790 / ASTM E108), Flammability of Exterior Walls (NFPA 285), and Evaluation Reports.

This campaign is part of a six part educational series of monthly articles featuring different topics that draw on UL’s history. To subscribe to the series, please click HERE or email firesafetyquote@ul.com for more information.