Recently, NFPA released an “Alert” regarding the hazards of antifreeze solutions in fire sprinkler systems. Antifreeze has become a popular alternative to compressed air for protecting sprinkler pipes from freezing in cold climates. In its undiluted form, however, antifreeze will exacerbate a fire instead of extinguishing it.    

Alerts such as these can serve to motivate businesses to re-evaluate their existing fire-protection solutions. This two-part column provides readers with some of the fundamentals about fire sprinklers and related fire-protection systems should they decide to undertake a re-evaluation.   

Motivation Factors
Every fire-protection system design should begin with clear definitions of the top-level objectives for the system. Life safety (protection of the structure to permit safe egress of occupants) should be an obvious motivation factor, but protection of a building’s contents and equipment should also be considered. At a minimum, applicable fire code requirements should be met.    

Tradeoffs are frequently important. One to consider is extinguishing efficacy versus negative consequences of agent in the protected space. Another tradeoff involves up-front system cost versus downstream costs to replace fire-damaged goods and infrastructure. Insurance loss-control experts can assist with these evaluations.  

Performance Objective
The inter-relationship of the various motivation factors will influence the basic “performance objective” of the automatic fire-protection system.    

The three categories of performance are: fire control (fire growth is stopped and heat damage is contained, but manual firefighter intervention is required to complete extinguishment); fire suppression (fire intensity is reduced by the automatic system, but manual extinguishment is still required on a smaller scale); and fire extinguishment (complete automatic suppression of a fire until burning is eliminated, without firefighter intervention).  

Occupancy and Commodity Classes
A fire-protection system design must also take into account the nature of the facility being protected (“occupancy”) as well as the nature of the combustible materials present (“commodity”).  For the purpose of sprinkler design, occupancies can be “light hazard” (e.g., churches, kennels and nursing homes), “ordinary hazard” (e.g., restaurants, machine shops and plastics molding) or “extra hazard” (e.g., die casting, solvent cleaning and oil quenching) spaces. 

More next time.