The Heat Is On: Striking a Balance Between Passive and Active Fire Protection

Chances are when you hear “fire protection,” the first items that come to mind are sprinklers, fire extinguishers, and alarm systems. While each of these are critical components, fire protection systems are comprised of much, much more.

To limit damage in the event of a fire, efficient fire protection systems are comprised of a balance of both passive and active protection.

Passive Fire Protection

Passive fire containment is one of the primary goals of fire resistance, and has the following functions:

• Protects occupants during emergencies
• Protects the spread of fire and smoke via vertical shaft opening
• Separates hazards
• Protects building systems and construction

The objective of passive protection is to buy time for the evacuation or relocation of occupants to a place of relative safety. Additionally, it can also allow firefighters the time to effectively evaluate and manage an emergency before conducting rescue and suppression operations.

Fire resistance ratings are based on the performance of the assembly evaluated in accordance with standard test methods ASTM E119 or UL 263. Ratings are stated in hourly or a combination of hourly and half-hour durations. Although published independently, ASTM and UL maintain active committees to ensure that these and other fire test methods commonly used by the building codes remain harmonized.

Testing is conducted by exposing the test assembly (walls, floor-ceilings, roof-ceilings, columns, beams, and horizontal membranes) to furnace conditions that follow a specific time and temperature curve. The assembly must not fail structurally, either by the passage of flames or by the transfer of heat sufficient to raise the unexposed surface temperature over a specified limit for the time of the rating period. These tests will take all factors into consideration for a pass or fail grade, down to the studs and fasteners, so it’s important to understand that each component of a fire-resistive assembly serves its function.

The best barrier for passive fire protection? Fire-rated gypsum board—provided by the principal raw material used in its manufacture, CaSO₄–2H₂O (gypsum). As the formula shows, gypsum contains chemically combined water (about 20% by weight). When gypsum panel products are exposed to fire, the heat converts a portion of the combined water to steam. The heat energy that converts water to steam is thus used up, keeping the opposite side of the panel cool as long as there is water left in the gypsum or until the panel is breached.

In fact, the common use of gypsum for fire protection date back to one of the earliest fire codes, issued by King Louis XIV of France in 1667, the year after the Great Fire of London. He wanted to protect his capital city, Paris, from suffering the same fate. Over the following decades the practice was emulated throughout Europe, leading to gypsum plaster becoming known by its common name: Plaster of Paris.

Active Fire Protection

The second method for fire protection is by utilizing active fire protection. This technique is dependent on the initiation of a system or human action to suppress or manage a fire. Examples of active fire protection are:

• Automatic sprinkler systems
• Gaseous, foam, or chemical agent systems
• Fire extinguishers
• Standpipes

This type of fire protection has become commonplace in today’s construction due to its significant reduction in the risk of fire growth and spread within buildings.

In Conclusion…

Fire protection does not boil down to just one product or system—it’s a coordinated effort, where the studs and fasteners are just as integral as the wallboard and sprinkler systems. For the greatest level of fire protection, it’s imperative to strike a balance using both passive and active methodologies. Active fire protection should never replace passive fire resistance design and construction, and vice versa.