A dry system is built in an attic with a damaged domed ceiling that blocks the sprinklers above. Approximately 60% of the ceiling is still intact, while sprinklers are spaced as seen below.

The AHJ has ordered that the entire ceiling be fixed using chicken wire and insulation to improve heat collection.

The ceiling may not need to be completely repaired as it is considered an impediment beyond 4 feet.

Question 1.  A dry system is installed in an attic with a damaged domed ceiling that prevents the sprinklers from functioning properly. Approximately 60% of the ceiling remains intact. The sprinklers are spaced as seen below. To improve heat collection, the AHJ has ordered chicken wire and insulation to be installed throughout the ceiling.

The ceiling may not require total restoration because it is deemed an obstruction beyond 4 feet.

Ans. A dry sprinkler system is being built in an existing church’s attic, which has a partially damaged and abandoned lath and plaster ceiling between the mid- and lower attics. The remaining ceiling, with chicken wire and insulation, exceeds NFPA 13’s 48-inch width threshold.

NFPA 13 recommends installing additional sprinklers below impediments of this magnitude, which have previously been implemented. The chicken wire insulation acts as a ceiling, collecting heat to activate supplementary sprinklers.

The supplementary sprinklers comply with NFPA 13 and effectively solve the obstruction. Your interpretation is right. The fire marshal’s request to replace the ceiling with chicken wire and insulation is unnecessary since the installed supplemental sprinklers have already addressed the obstruction in line with NFPA 13.

The project includes an Extra Hazard Group 1 (EH1) area, with the remainder classified as Ordinary Hazard Group 2. The EH1 space adheres to the room design standards of Section 28.2.4.1.1 of NFPA 13 (2025 edition). The query seeks confirmation whether the ‘Phantom Flow’ criterion from Section 28.2.4.2.5 is applicable to this room design method.

Question 2. The project comprises an Extra Hazard Group 1 (EH1) region, and the rest is designated as Ordinary Hazard Group 2. The EH1 space meets the room design technique standards outlined in Section 28.2.4.1.1 of NFPA 13 (2025 edition).

Please confirm whether the ‘Phantom Flow’ criterion from Section 28.2.4.2.5 applies to the room design approach.

Ans. The phantom flow notion in Section 28.2.4.2.5 only applies to the density/area calculation approach, not the room design method.

This distinction is clear from the section numbering. Section 28.2.4.1 covers the Room Design Method, whereas Section 28.2.4.2 addresses the density/area method. Section 28.2.4.2.5 (phantom flow) is a subsection of 28.2.4.2 and only applies to projects that use the density/area method.

Additionally, Section 28.2.4.1 (Room Design approach) does not include a phantom flow requirement, indicating that it does not apply to this approach.

The project involves an underground loop with various lead-ins for the sprinkler systems. The owner/general contractor does not believe isolation valves are necessary for each sprinkler system lead-in.

Question 3. Do all lead-ins require an isolation valve?

Ans. Yes. According to Section 6.2.9 of the 2016 version of NFPA 24, all connections must be isolated using a valve. This section provides alternatives for arranging valves to ensure isolation at each connection.

While NFPA 24 does not expressly define “connection,” a sprinkler system lead-in is considered a connection under Section 6.2.9. This view is backed by Annex A.6.6.1, which covers sectional valves. The appendices say:

“Fire protection connections can consist of sprinkler system lead-ins, hydrants, or other fire protection connections.”

This phrase explicitly states that a lead-in is a form of connection. Section 6.2.9 requires that each lead-in or connection be isolated.

One level of an NFPA 13R residential structure will be renovated to a light hazard area.

The current 2-inch incoming service meets hydraulic calculations for the light hazard space. The 2-inch service line serves both the fire sprinkler system and household purposes.

Question 4. Is it necessary to convert the main to a 4-inch incoming service and a 4-inch backflow preventer, or can the 2-inch service still fulfil the required calculations?

Ans. Yes, a 2-inch service might be acceptable. NFPA 13 (2016 Edition) – Section 24.1.3.3 offers recommendations in this case. It reads: “24.1.3.3.” If a single main less than 4 in. (100 mm) in diameter serves both fire systems and other uses, the non-fire demand must be added to the hydraulic calculations for the fire system at the point of connection, unless automatic isolation is provided during a fire event.

Existing structures often have lesser water supplies than the “standard” 4-inch requirement. A diverter valve on the household water line closes when sprinklers activate, dedicating the whole supply to fire protection.

Domestic demand can be added to sprinkler demand if hydraulic calculations show adequate system capacity. NFPA 13R provides guidelines for calculating household water fixture usage.

Section 24.1.2 necessitates including the hose stream allowance in hydraulic calculations.

A new elementary school is being built on 57,885 square feet. The architectural drawings depict a single shotgun riser. The building has bulk pipes and zone valves that supply sprinklered areas such as the gym.

Question 5. Is this arrangement permissible? A single riser can only supply up to 52,000 square feet, according to the law.

Ans. The building requires two risers due to its overall square footage, which exceeds the maximum of 52,000 square feet per riser. However, various factors can impact this requirement:

Are the “zone valves” in the design simple isolation valves or floor control valve assemblies? Sprinkler systems with valves, check valves, gauges, drains and flow switches are regarded as independent.

The 2025 version of NFPA 13 raises the maximum area for light hazard wet pipe systems to 78,000 square feet, up from 52,000 square feet.

This question is based on the 2019 edition of NFPA 13, but some Authorities Having Jurisdiction (AHJs) may accept language from newer editions. Many AHJs may approve a single system if they grasp the rationale for the 52,000 square foot limit, even if the square footage somewhat exceeds it. Some AHJs carefully adhere to the standard, which stipulates “52,000 square feet maximum per system.”

Previous editions of NFPA 13, such as the 1953 edition, have unique design limitations. Sprinklers in light hazard systems can be spaced up to 196 square feet apart, and there is no restriction to the number of sprinklers per system. Ordinary hazard systems had a maximum spacing of 130 square feet per sprinkler and were typically limited to 400 sprinklers per system, resulting in the 52,000 square foot limit.

When hydraulic calculations were established, the Sprinkler Committee saw the necessity to limit system sizes planned utilizing hydraulic methods over the pipe schedule method. The 52,000 square foot limit was a reasonable decision for system size constraints. Older standards did not limit the size of light hazard systems, allowing an AHJ to serve a broader area with a single riser.

The AHJ has the final power to decide acceptable tolerances for applying NFPA standards.

K16.8 ESFR sprinklers with 12 heads at 52 psi are installed in a warehouse building measuring 40 feet in height. The facility is looking for a tenant who will store rolled carpet.

The 2010 edition of NFPA 13 does not include rolled carpet storage; hence, design requirements are based on FM Global Data Sheet 8-30. The tenant will use regular carpet racks instead of cubicles or tubes for storage.

The proposed protection solution involves

• installing a ceiling at a maximum height of 30 feet and,
• limiting storage height to 12 feet, as per Table 1 of FM 8-30.
• Following the design criteria in Table 1
• No storage above the carpet level

Question 6. The tenant is requesting a third-party evaluation of the assessment and has asked the following questions:

1. Are there any other codes or standards for this storage commodity?
2. Is there an alternate design for storage above 12 feet that doesn’t require in-rack sprinklers?
3. Can products like carpet tiles in cardboard boxes be placed above the rolled carpet (above the 12-foot mark) to maximize available space?

Ans. To answer particular queries, it’s vital to first understand how NFPA 13 applies to rolled carpet storage.

The 2010 edition of NFPA 13 does not expressly specify that rolled carpet falls beyond its scope.

In 2016, Annex Table A.5.6 (Examples of Commodities Not Addressed by Classifications in Section 5.6) was updated to include rolled carpet. First Revision #290 offered an update to identify commodities that cannot be protected using NFPA 13 schemes.

The inclusion of rolled carpet in Table A.5.6 should not be overlooked, even though it is only mentioned in the annex and not in the 2010 edition.

Storing rolled carpet in racks can block required flue spaces, posing a difficulty under NFPA 13.

Section 17.1.10.1.1 mandates a transverse flue space at rack uprights and between loads, resulting in a space every 4 to 5 feet within the rack.

Storing carpet rolls horizontally can obstruct flue spaces, resulting in a solid shelf rack.

Section 17.1.5.1 mandates in-rack sprinklers at 6-foot intervals when flue space obstruction exceeds 20 square feet.

The 2016 edition of NFPA 13 clarified the definition of solid shelving (3.9.3.8), stating:

“…or by the placement of loads that block openings that would otherwise serve as the required flue spaces…”

FM Global Property Loss Prevention Data Sheet 8-30, which covers carpet storage, is recommended.

Question 1: Are there any other codes or standards for this storage commodity?

Answer: NFPA 13 (beginning with the 2016 version) excludes rolled carpet from its prescriptive scope. There are no alternate codes or standards for this storage commodity other than FM Data Sheet 8-30.

Question 2: Is there an alternate design for storage over 12 feet without in-rack sprinklers?

Answer: There are no prescribed standards for storing items larger than 12 feet without in-rack sprinklers, according to accessible information.

Question 3: Can carpet tiles in cardboard boxes be kept above rolled carpet (above the 12-foot mark) to maximise available space?

Answer: Yes, however, the protective criterion must meet the most rigorous condition, which appears to be in-rack sprinklers.

Section 2.4.3.2 of FM 8-30 recommends installing in-rack sprinklers at the top of a carpet storage rack if the clearance between the top of storage and the overhead ceiling exceeds 20 feet (6.0 m). This ensures that only one tier of storage is above the top level of sprinklers.

Given the available facts, the decision to use FM Data Sheet 8-30 is justified. According to existing guidance, there is no less stringent prescriptive protection scheme available for this storage configuration.

The question asks whether there is a specific rule for estimating the slope of an oval ceiling compared to a flat ceiling. It seeks clarification on guidelines or formulas that may apply when dealing with oval ceilings in design or engineering contexts.

Question 7. Is there a rule for estimating the slope of an oval ceiling vs. a flat ceiling?

Ans. NFPA 13 recommends measuring sprinkler distances along a circular ceiling slope. To determine sprinkler spacing, follow the curvature of the rounded surface and treat the ceiling as a slanted plane during calculation.

In the 2025 edition of NFPA 13, Sections 9.5.3 and 10.2 address sprinkler spacing and sloped or rounded ceiling restrictions.

The question asks where in the NFPA codes/standards or the National Electrical Code (NEC) it is stated that air compressors for dry pipe systems must be hardwired instead of being plugged into an outlet. It seeks clarification on specific requirements for the electrical connection of these compressors.

Question 8. Where does it state in NFPA codes/standards or the National Electrical Code that air compressors for dry pipe systems must be hardwired rather than plugged into an outlet?

Ans. This criterion was not addressed in the 2013 or previous editions of NFPA 13. The 2016 model required a specialized air compressor.

The electrical circuit must be installed in compliance with Article 430 of the National Electrical Code (NFPA 70).

In the 2025 edition of NFPA 13:

• According to Section 8.2.7.5.4, air compressors used as dedicated air supplies must be installed in compliance with NFPA 70, Article 430.
• According to Section 8.2.7.5.5, automatic air compressors cannot be disconnected using a general-use switch or cord-and-plug connection.

Furthermore, the 2025 edition requires compressors to be listed.

The facilities manager confirmed that a little puddle on the riser is usual during weather or temperature changes.

Question 9. Is this level of leakage considered acceptable? Is any level of leakage allowed?

Ans. Identifying the source of the leaking can be challenging based on the image.

If the leak originates in the riser, no quantity of leakage is acceptable. According to NFPA 13, Section 5.2.2.1, plumbing and sprinklers must be leak-free.

If the moisture comes from the slab, NFPA 25 does not specifically handle this problem.

However, it is a good idea to document the problem and notify the owner. External variables, like water incursion or structural concerns, can cause seepage in both the flooring and sprinkler system pipework over time. Encouraging the owner to examine the source of seepage can avert long-term damage and system failure.

A mixed-use building has business space on the basement and first floor and residential units on the second and third floors. There is a sprinklered concealed gap between business and residential areas.

Question 10. Is it permissible to employ an NFPA 13R sprinkler system on the residential floors?

Ans. In a mixed-use building with commercial spaces on the basement and first floors and residential spaces on the second and third floors, an NFPA 13R sprinkler system can be used for the residential floors under certain criteria defined in the 2018 IBC and 2016 NFPA 13R regulations. Consider whether the building is classified as separated or non-separated occupancy.

Separated Occupancies: NFPA 13R can be used for residential floors with a fire-resistant barrier to separate residential and commercial spaces. This obstacle

IBC regulations, normally 2 hours or 1 hour if both sides are sprinklered per NFPA 13, apply to concealed areas, walls, and floors. The presence of a sprinklered concealed space is crucial, although it does not affect the necessary rated separation.

Non-Separated Occupancies: Non-separated buildings have stricter fire safety regulations, requiring the usage of NFPA 13 throughout.

NFPA 13R specifies that residential buildings can be up to four stories tall and no higher than 60 feet above ground level.

• NFPA 13R cannot be employed if the building was planned with code trade-offs, such as greater height or area allowances, as per NFPA 13.
• Authority Having Jurisdiction (AHJ) Approval: NFPA 13R A.1.1 specifies that the standard applies to residential occupancies that are suitably separated from non-residential uses. Model codes may have additional constraints, requiring AHJ consultation to ensure compliance.

To summarise, NFPA 13R can be used on residential floors if the necessary separation is established.

• The building meets IBC height and story regulations.
• No NFPA 13 trade-offs were used.

Coordination with the architect and AHJ is crucial to ensure NFPA 13R compliance in the design.

The question asks whether it is permissible to remove sprinklers from a non-combustible external canopy over a pier designed for temporary product drop-off and pick-up, rather than for storage. It seeks clarification on fire protection requirements for such canopies.

Question 11. Is it possible to remove sprinklers from a noncombustible external canopy over a pier used for temporary product drop-off and pick-up, rather than storage?

Ans. Sprinklers can be excluded from non-combustible external overhangs for short-term storage, such as delivered items.

NFPA 13, 2022 edition, Section 9.3.19.2 requires sprinklers to be fitted under all outside projections greater than 4 feet where combustibles are housed. According to Annex Section A.9.3.19.2, short-term temporary storage, such as for delivery parcels, is not suitable for storing or handling combustibles.

Short-term transient storage, such as for delivering packages, is not considered storage and does not require sprinkler protection under the standard.

In a light hazard occupation, an upright sprinkler is placed 16 inches above a 30-inch duct, with an additional sprinkler beneath it. Another upright sprinkler.

Question 12. Place the sprinkler 12 feet 0 inches above the duct and 10 feet 6 inches from the midline on the opposite side. See the figure.

Is additional sprinkler coverage needed on the opposite side of the duct within 7 feet-6 inches of the centerline?

Ans. Installing a sprinkler under the duct eliminates the need for an additional sprinkler above it (within 7.5 feet of the centerline). Because there is a sprinkler beneath the obstacle, the ceiling sprinklers above do not consider the shielded duct an obstruction.

In the 2025 edition of NFPA 13, Section 10.2.8.3 applies to obstructions “below the obstruction” but less than 18 inches below the deflector. This section provides the designer with numerous alternatives for dealing with the impediment.

Section 10.2.8.3.1.4 (Three Times Rule) is the base obstruction rule for this case. However, it does not apply if the prerequisites of 10.2.8.3.1.5-10.2.8.3.1.10 are met.