In a commercial Building (a hanger I'm working on) How close can lights or other things be to the sprinkler head? is there a distance below or horizontally? I've heard 18" but it seems like directly below would allow the head to spray out better. Whats the fire code on this?
The Golden Rule - "The man with the gold makes the rule"
Per 2002 NFPA 13 (the sprinkler code) Table 18.104.22.168(c), 0-250 W light fixture requires a minimum distance of 6 inches from ordinary-temperature sprinklers, and 3 inches from intermediate-temperature sprinklers. Also, 250-499 W fixtures require a clearance of 12 and 6 inches respectively.
Any fixture within the spray pattern would have to be considered in the design by the engineer or certified installer to allow full coverage despite the obstruction.
The title of Table 22.214.171.124(c) is: Ratings of Sprinklers in Specified Residential Areas. In other than residential situations, 126.96.36.199 requires the sprinkler head temperature rating to be adjusted. Item (6) requires: Sprinklers in unventilated show windows having high-powered electric lights near the ceiling shall be of the intermediate-temperature classification. To get an answer to your question, you will have to consult the sprinkler engineer or installer.