STRIKING A BALANCE BETWEEN PASSIVE AND ACTIVE FIRE PROTECTION

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One of the most critical issues for every construction professional is ensuring that building design addresses fire-safety issues. All buildings—new and old—are susceptible to the threat of fire and the resulting damage to property and life.

By definition, fire resistance is the ability of building components to contain and limit the spread of a fire within an assembly. According to the International Building Code® (IBC®), there are two types of fire protection methodologies to consider within any design—passive and active. 

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 openings 
  • 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 or to allow firefighters the time to evaluate and manage an emergency and conduct rescue and suppression operations.

Passive fire resistance ratings are based on the performance of the assembly to withstand the failure criteria of standard test methods ASTM E119, UL 263 and NFPA 251. Ratings are stated in hourly or a combination of hourly and half-hour durations.  Although published independently, ASTM, UL and NFPA maintain an active committee on harmonization to ensure that these and other fire test methods commonly used by the building codes remain consistent.

Testing is conducted by exposing the test assembly (partition, floor-ceiling, roof-ceiling, column, beam and membranes) to furnace conditions that follow a specific time and temperature curve.  The assembly must not fail structurally, or 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.

The best barrier for passive fire protection? Fire rated gypsum board—it is made up of 20% chemically combined water; using it as a passive fire design has been a common practice for over 50 years.  

The use of gypsum boards for fire protection dates back 100 years although “over 50 years” for “common  practice” accurately refers to the post-WWII building boom.  The common use of gypsum for fire protection dates 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 and gypsum plaster came to be known as 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 as it has demonstrated significant reductions to the risk of fire growth and spread within buildings. 

WHAT YOU NEED TO KNOW 

For the greatest level of fire protection, it’s imperative that a balance be struck using both passive and active methodologies. Active fire protection should never replace passive fire resistance design and construction, and vice versa. To most effectively ensure fire and life safety, passive and active fire design should be implemented.