Fuel and Ventilation
The quantity of combustibles in a space and their location (e.g., high elevations, stacked against walls, etc.) also play roles in determining preferred fire-protection designs. For rack storage or other spaces with obstructions that could impede the effective application of water from ceiling-mounted sprinklers, spray nozzles at different elevations may be necessary. The supply of fresh air into a space by natural and mechanical means also impacts design choices.  

Extinguishing Agents
Different extinguishing agents are well suited for different occupancies and commodities. Liquid water is the most common extinguishing agent, but steam, carbon dioxide, dry chemicals (e.g., bicarbonate of soda), wet chemicals (e.g., aqueous solution of potassium carbonate and/or potassium acetate) and other materials may be preferred for some hazards.   

Detector, Nozzle and Pipe Variables
When water is selected as the extinguishing agent, a number of nozzle styles are available (sprinkler, water spray, water mist and steam). Choices also exist for piping and valve design (e.g., wet pipe, dry pipe, deluge, circulating, preaction and antifreeze). Detectors can be mechanical (fusible links) or electrical (temperature switch or fused contacts).   

Special Hazards
Special fire-protection solutions are often implemented for special hazards. The interior of processing equipment may be incompatible with conventional sprinklers due to chemicals or extreme temperatures and pressures. Such locations could be best served by inert gas or other extinguishing agents. Ducts that convey combustible particulate matter may require spark-detection and rapid extinguishing-agent discharge to prevent a deflagration and explosion. Non-metal, product-conveying ducts and plenums should be manufactured with fire-retardant material or protected by sprinklers.  

Obviously, the design of an effective fire-suppression system involves numerous subsystems and many choices for the plant owner. In Part 3, some specific fire-protection examples will be discussed along with reasons to select or avoid many of these design choices.