NFPA 14 · NFPA 30 · NFPA 780

NFPA 14, 30 & 780 explained: standpipes, flammable liquids & lightning protection

Standpipe classes and the flow/pressure concept, flammable vs combustible liquid classes with the OSHA jobsite storage limits, and the parts of a lightning protection system — with worked examples.

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NFPA 14 — Standpipe systems

NFPA 14 — standpipe classes, in plain words

Class	Who uses it	What’s at the outlet (concept)
Class I	Fire department (and trained brigades)	Large hose connections for fire-department hose; no hose stored on site
Class II	Building occupants / trained personnel	Smaller hose stations, often with hose in a cabinet
Class III	Both	Both connection types on the same system

System type (automatic vs manual, wet vs dry) is a separate choice from class. Our own summary, not the standard text. Read NFPA 14, 30, and 780 in the free NFPA viewer (nfpa.org/freeaccess) and verify against the editions adopted by your AHJ. Not engineering advice.

Worked example — Class I standpipe, single riser (concept)

Input / step	Value	Source
Building	Sprinklered, one Class I standpipe in the stair	Design
Flow at the hydraulically most remote standpipe	500 gpm	Class I flow requirement
Residual pressure at the most remote hose connection	100 psi	Class I pressure requirement
What it means for the pump	Deliver 500 gpm at 100 psi at the top outlet after elevation and friction	Hydraulic calc by the designer
More standpipes?	Additional flow per extra standpipe, up to a cap	Check the standard — not calculated here

Illustrative only; not a hydraulic calculation. Look up the full criteria in the free NFPA viewer.

NFPA 30 — Flammable & combustible liquids

NFPA 30 — how liquid classes are organized (concept)

Group	Basis	Why it matters
Flammable liquids (Class I, subdivided IA/IB/IC)	Flash point below the flammable/combustible dividing line; subclasses also use boiling point	Tightest limits on quantity, containers, and ignition sources
Combustible liquids (Class II and Class III, III subdivided IIIA/IIIB)	Flash point at or above the dividing line, grouped by higher flash-point bands	Larger allowable quantities, fewer restrictions
How to find a product’s class	Flash point (and boiling point) from the SDS, Section 9	The SDS is the jobsite source of truth

OSHA now uses GHS Categories 1–4 for flammable liquids; NFPA 30 and the fire code keep Class I/II/III. Our own summary, not the standard text. Read NFPA 14, 30, and 780 in the free NFPA viewer (nfpa.org/freeaccess) and verify against the editions adopted by your AHJ. Not engineering advice.

Worked example — classifying two jobsite fuels

Liquid	Flash point (from SDS)	Result
Gasoline	Far below 100°F	Flammable (Class I under NFPA 30) — safety cans, cabinet limits apply
Diesel fuel	Typically above 100°F (check the SDS)	Combustible (Class II under NFPA 30) in most cases

100°F is the NFPA 30 dividing line between flammable and combustible liquids. Always read the actual product SDS.

OSHA 29 CFR 1926.152 — jobsite flammable-liquid storage (public domain — key limits)

Rule	Limit	Citation
Handling and use in quantities of 5 gallons or less	Approved safety cans or DOT-approved containers (except highly viscid liquids); original container OK for 1 gallon or less	1926.152(a)(1)
Storage locations	Not in exits, stairways, or areas normally used for safe passage of people	1926.152(a)(2)
Indoors, outside an approved storage cabinet	No more than 25 gallons in a room	1926.152(b)(1)
Per storage cabinet	No more than 60 gallons of Category 1, 2, and/or 3, or 120 gallons of Category 4	1926.152(b)(3)
Cabinets per storage area	No more than 3; more requires an inside storage room	1926.152(b)(3)
Cabinet label	“Flammable-Keep Away from Open Flames.”	1926.152(b)(2)(iii)

Federal OSHA text (29 CFR 1926.152, verified against eCFR). State-plan states and the local fire code may be stricter.

NFPA 780 — Lightning protection

NFPA 780 — the components of a lightning protection system

Component	Job it does	Field notes
Strike termination devices (air terminals, masts, overhead wires)	Intercept the strike	Placed at ridges, edges, corners, and across flat roofs per spacing rules
Main conductors (roof and down conductors)	Carry current from terminals to ground by the most direct path	Avoid sharp bends; two-way paths from each terminal
Grounding electrodes	Dissipate current into earth	Rods, rings, plates, or concrete-encased electrodes depending on soil
Bonding	Tie nearby metal bodies in so current doesn’t side-flash	Bond to the electrical grounding electrode system
Surge protection	Protect services entering the building	SPDs at electrical, telecom, and data entrances
Materials class (Class I vs Class II)	Heavier (Class II) materials for taller structures	The height threshold sets which catalog applies

NFPA 780 is a design/installation standard; UL 96A covers listed installations. Our own summary, not the standard text. Read NFPA 14, 30, and 780 in the free NFPA viewer (nfpa.org/freeaccess) and verify against the editions adopted by your AHJ. Not engineering advice.

Worked example — low-rise flat-roof building (concept)

Input / step	Value	Source
Building height	40 ft	Plans
Materials class	Class I (structure not over 75 ft)	Materials-class height threshold
Perimeter air terminals (standard short terminals)	Spaced no more than 20 ft apart	Terminal spacing rule
Open flat-roof area	Additional terminals per the flat-roof rules	Check the standard
Down conductors and grounding	Count and spacing by perimeter; electrodes at each down conductor	Check the standard

Illustrative only. Taller terminals, rolling-sphere zones, and roof types change the layout.

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Three standards the other trades bump into

Read all three in the free NFPA viewer. NFPA offers read-only access to current editions at no cost. This page explains the concepts; it does not reproduce the standards’ tables. Editions referenced: NFPA 14-2024, NFPA 30-2024, NFPA 780-2023 — verify against the editions adopted by your AHJ.

NFPA 14 — standpipes. The class tells you who the system is for: Class I for the fire department, Class II for occupants, Class III for both. For Class I, the design idea is flow at the most remote standpipe with a minimum residual pressure at its top outlet — 500 gpm at 100 psi — plus added flow for additional standpipes. In a high-rise that usually means a fire pump, and in the field it means hose valves at the right height, the FDC where the fire department expects it, and the hydrostatic test done before walls close.

NFPA 30 — flammable and combustible liquids. Liquids are classed by flash point (and, for the most volatile, boiling point). The split between flammable and combustible is 100°F. For jobsite storage, the federal rule is OSHA 1926.152, which is public domain — its key storage limits are listed above; the local fire code, which references NFPA 30, can add limits.

NFPA 780 — lightning protection. A system is a chain: terminals intercept, conductors carry, electrodes dissipate, and bonding plus surge protection keep the current from jumping into the building’s own metal and wiring. Structures up to 75 ft use Class I materials; taller ones use heavier Class II materials. Standard short air terminals along a roof edge are spaced no more than 20 ft apart. Electricians should coordinate the lightning ground with the electrical grounding electrode system — they must be bonded.

Related references: the NFPA 13 sprinkler guide, the NEC 250.66 grounding electrode conductor guide, the IEEE grounding standards guide, and our free hot work permit template. Field PM keeps standpipe hydro tests, lightning protection certifications, and safety inspections with the job.

FAQ

What is the difference between Class I, II, and III standpipes?+

Class I has large hose connections for the fire department. Class II has smaller hose stations meant for occupants or trained staff. Class III has both. Read NFPA 14 free at nfpa.org/freeaccess.

How much flow and pressure does a Class I standpipe need?+

The most remote Class I standpipe is designed for 500 gpm with 100 psi residual pressure at the most remote hose connection, with added flow for additional standpipes up to a cap. The hydraulic calculation is the designer’s job.

What is the difference between a flammable and a combustible liquid?+

Under NFPA 30, flammable liquids (Class I) have flash points below 100°F and combustible liquids (Class II and III) are at or above it. Get the flash point from Section 9 of the product’s SDS. OSHA now uses GHS Categories 1–4 instead.

How much gasoline can I store on a construction site?+

Under federal OSHA 1926.152, no more than 25 gallons of flammable liquids may be stored in a room outside an approved storage cabinet; a cabinet holds no more than 60 gallons of Category 1–3 liquids (120 of Category 4), with no more than three cabinets per storage area. Handling containers of 5 gallons or less must be approved safety cans or DOT containers. Your fire code may be stricter.

What are the parts of a lightning protection system?+

Strike termination devices (air terminals), main and down conductors, grounding electrodes, bonding of nearby metal, and surge protection at service entrances. NFPA 780 uses Class I materials for structures up to 75 ft and heavier Class II materials above that.

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