NFPA 13 (2016 Edition) Section 126.96.36.199 requires sprinklers to be installed underneath fixed obstructions over 4ft (48") in width and provides no further information on how that 4ft width is determined to be an obstruction. For most situations this is rather straightforward, but the open ended 4ft wide requirement leaves quite a few obstructions up to interpretation.
With that being said, how is it determined that an obstruction such as a duct, can be considered unobstructed if it is 40" wide by 6ft long, but if it is 48" wide by 3ft long, it is considered an obstruction? How is the obstruction rule only applied to the width of a piece of equipment and in turn is not applied to the length?
Is there a ratio or rule of thumb that is widely used to determine whether an item hanging below the ceiling is considered to violate the 4ft rule?
Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
Subscribe and learn something new each day:
Thank You to Our Top
June 2020 Contributors!
Sprinkler Designer or Engineer?
Get all of our tools, including the Sprinkler Database, Friction Loss Calculator, Fire Pump Analyzer and more:
Daily discussion questions are open-ended questions posed by members for the benefit of sharing expertise and learning from other perspectives. Join as a member here.
2020 PE Prep Guide
PE Prep Series
2020 PE Prep Series
(Click to enlarge)
Visit July-October for daily Fire Protection PE Exam sample questions.
Solutions are posted the day after posting.
Comment with your solutions, questions or clarifications.
Please note that questions posted are unofficial and in accordance with NCEES rules are intended to be similar to actual exam questions, not actual exam questions themselves.