Every state has different laws governing the positioning of fire sprinklers, but all states must follow certain federal laws. Federal law states that fire sprinklers must be positioned and located to provide satisfactory performance in terms of activation time and distribution. Sprinklers can have different clearance requirements from structural members and ceilings if they are specifically tested to show that their ability to sense, control and suppress a fire is not impaired.
Maximum Protection Area Per Sprinkler
Sprinklers cannot exceed the maximum protection area per sprinkler. According to the National Fire Protection Association’s Standard for the Installation of Sprinkler Systems 2010 Edition, the specific formula for determining the protection area of coverage per sprinkler -- where A1 is the protection area -- is A1 = S x L. S is defined as whichever is larger: either twice the distance between sprinkler to sprinkler or between sprinkler and a wall or obstruction, upstream and downstream. L is defined as whichever is larger: the perpendicular distance to the sprinkler on the adjacent branch line, or the perpendicular distance between the sprinkler and a wall or obstruction.
Maximum and Minimum Sprinkler Distance
Section 184.108.40.206.2 states that the maximum sprinkler coverage area shall not exceed 400 square feet. The standard also states that the maximum distance between sprinklers is based on the centerline distance between adjacent sprinklers and shall be measured along the slope of the ceiling. Sprinkler distance to a wall cannot exceed one-half of the maximum distance between sprinklers. The distance from the wall to the sprinkler is measured perpendicular to the wall behind furniture. The minimum distance between sprinklers should prevent operating sprinklers from wetting adjacent sprinklers and prevent sprinkler skipping.
Sprinkler Distance from Heating Ducts and Unit Heaters
Sprinklers of ordinary and intermediate temperature must be located more than 2 feet, 6 inches above a heating duct and uncovered steam main, and more than 1 foot to the side and below. Sprinklers of an ordinary temperature located adjacent to a heating duct discharging air less than 100 degrees F do not have to be separated according to these rules. High-temperature sprinklers must be located in a seven-foot radius cylinder extending seven feet above and 2 feet below a unit heater with horizontal discharge.
Sprinkler Distance from Other Heat Sources
Section 220.127.116.11 states that sprinklers located within 12 inches to one side or 30 inches above an uncovered radiator, steam main or heating coil are classified as intermediate-temperature. Sprinklers within 7 feet of a low-pressure blowoff valve discharging free in a large room are classified as high-temperature. Table 18.104.22.168(c) shows that ordinary-temperature sprinklers must be located at least 36 inches from the side of an open or recessed fireplace; 60 inches from the front of a recessed fireplace; 42 inches from a coal or wood-burning stove; 18 inches from a kitchen range, wall oven, hot air flue or uninsulated heat duct; 12 inches from an uninsulated hot water pipe; 24 inches from the side of a ceiling or wall-mounted hot air diffuser; 36 inches from the front of a wall-mounted hot air diffusers; 6 inches from a hot water heater or furnace; 6 inches from a light fixture from 0 W to 250 W and 12 inches from a light fixture from 250 W to 499 W. These measurements are generally less for intermediate-temperature sprinklers.