CFC · California Fire Code

Unstable (reactive) and water‑reactive materials: control area limits and storage/use safeguards

Q: What is the first thing I must check before deciding storage rules for these materials?

Check the maximum allowable quantity (MAQ) per control area in Section 5003.1 / Table 5003.1.1 . If your planned quantity exceeds the MAQ, Chapters 50 and 66/67 impose additional engineering, separation, and permitting requirements.

Q: Can I store Class 3 or 4 unstable materials in an office or a residence?

No. Class 3 and 4 unstable materials are prohibited in Group R occupancies and are prohibited in ordinary offices (Groups B, F, M, S) per § 6603.1.2.2–.4 .

Q: Do water‑reactive materials need special containers?

Yes — Class 3 water‑reactive solids and liquids stored in areas with sprinklers must be in closed watertight containers ; rooms must be waterproof and piping conveying water (except sprinklers) is restricted. § 6704.1.3–.4 .

Q: What pile size and aisle width do I need indoors?

If storage exceeds 500 cubic feet , separate into piles that are no larger than 500 cubic feet ; aisles must be at least the height of the piles or 4 feet , whichever is greater ( § 6604.1.4 / § 6704.1.5 ).

Q: Who enforces these limits and do I need a permit?

Local fire code officials enforce the CFC provisions; permits are required as set out in Section 105.5 and the permit requirements are referenced in § 6601.2 and § 6701.2 . Consult your local authority having jurisdiction (AHJ).

If you store unstable or water‑reactive materials, first check the maximum allowable quantity per control area in Section 5003.1/Table 5003.1.1; if your quantity exceeds that MAQ you must follow Chapter 50 and the detailed storage rules in Chapters 66 (unstable) and 67 (water‑reactive) — including limits on pile size (500 cu ft indoor), aisle widths, minimum separations (20 ft or 75 ft outdoors depending on class), liquid‑tight floors, watertight containers for certain water‑reactives, and explosion control where required.

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Last reviewed: July 6, 2026

What the code requires — plain English

The California Fire Code requires that storage and use of UNSTABLE (REACTIVE) MATERIALS and WATER‑REACTIVE MATERIALS be limited to the maximum allowable quantity per control area shown in Section 5003.1 (Table 5003.1.1) and that any amounts exceeding those limits follow the stricter building‑ and fire‑protection provisions in Chapters 50 and 66/67. The general rules and occupancy limits for unstable materials are in § 6601 and § 6603; storage details (indoor/outdoor piles, distances, containers, explosion control, basement prohibitions, floors) are in § 6604 for unstable materials and § 6704 for water‑reactives.

The single most important rule: always check the maximum allowable quantity per control area in Section 5003.1 / Table 5003.1.1 — if your quantity exceeds that MAQ, storage and use must be treated as a control‑area overlimit and follow Chapter 50 plus the specific provisions of Chapters 66 and 67.

Requirements in detail

Scope and definitions (what materials are covered)

Scope: Chapter 66 covers unstable (reactive) materials (solids, liquids, compressed gases); Chapter 67 covers water‑reactive solids and liquids. See § 6601 and § 6701.
Definitions for the classes (Class 1–4) are located in the code’s Chapter 2 and are referenced in § 6602 and § 6702.

Control‑area limits and what to do if you exceed them

The numeric maximum allowable quantity (MAQ) per control area is established in Section 5003.1 (Table 5003.1.1). Quantities not exceeding the MAQ follow ordinary storage rules; quantities exceeding the MAQ must comply with Chapter 50 and the applicable sections of Chapters 66/67. § 6603.1 and § 6703.1–6703.2 state and enforce this linkage.
IMPORTANT: I did not retrieve the full Table 5003.1.1 values in the files provided here — consult Section 5003.1 / Table 5003.1.1 in your code or local authority for the exact MAQ numbers.

Occupancy‑specific limits (unstable/reactive)

Some occupancies prohibit certain classes: Class 3 and 4 unstable materials are not allowed in Group R; Class 4 is not allowed in retail portions of Group M; Class 3 and 4 cannot be stored in ordinary offices of Groups B, F, M, or S; classrooms have special cabinet requirements. These limits are in § 6603.1.2.2 – § 6603.1.2.5.

Indoor storage — configuration, floors, explosion control

Floors for storage areas must be liquid‑tight per Section 5004.12 and the chapter‑specific requirements in § 6604.1.3 and § 6704.1.2.
Explosion control is required for indoor rooms/areas containing certain classes: unstable Class 3 or 4 storage requires explosion control per § 6604.1.2; water‑reactive Class 2 or 3 indoor storage requires explosion control per § 6704.1.6 (Section 911 is the referenced method).

Pile size, separation and aisle widths (decision‑relevant numeric limits)

Indoor pile limits and aisle widths:
- Quantities > 500 cubic feet must be separated into piles each not larger than 500 cubic feet; aisle width shall be not less than the height of the piles or 4 feet, whichever is greater. § 6604.1.4 (unstable) and § 6704.1.5 (water‑reactive) contain these indoor requirements.
Outdoor pile limits and aisle widths:
- Outdoor piles of unstable materials shall not exceed 1,000 cubic feet (unstable) and aisle widths between piles shall be not less than one‑half the height of the pile or 10 feet, whichever is greater (see § 6604.2.4–6604.2.5). Water‑reactive outdoor pile limits differ by class — see § 6704.2.4.

Distance / separation to exposures (outdoor)

For unstable materials:
- Outdoor storage of Class 2 or 1 unstable materials shall not be located within 20 feet of buildings, lot lines, public streets, alleys, public ways or means of egress, unless a 2‑hour fire barrier without openings interrupts the line of sight. § 6604.2.3.
- Distances for detonable Class 3/4 materials and deflagratable Class 3 follow specific tables (Table 5604.5.2(2) and (3)) referenced in § 6604.2.1–6604.2.2.
For water‑reactive materials:
- Outdoor Class 3 water‑reactive shall not be within 75 feet of buildings, lot lines, streets, alleys or means of egress (§ 6704.2.2).
- Outdoor Class 2 water‑reactive shall not be within 20 feet, unless a 2‑hour fire barrier constructed as specified is provided (§ 6704.2.3).

Containers and waterproofing (water‑reactive)

Where Class 3 water‑reactive solids and liquids are stored in areas that have an automatic sprinkler system, they must be in closed watertight containers (§ 6704.1.4). Rooms for water‑reactives must be waterproof and piping carrying water (except sprinkler piping) is not allowed within these rooms (§ 6704.1.3).

Basements and incompatibles

Unstable materials shall not be stored in basements (§ 6604.1.5). Water‑reactive Class 3 shall not be stored in basements; Class 2 may be stored in basements only if in closed watertight containers or tanks (§ 6704.1.5). Class 2 or 3 water‑reactives shall not be stored with flammable liquids.

Indoor cabinets and laboratory/occupancy exceptions

In certain occupancies (Group A, E, I, U, classrooms), Class 3 and 4 unstable materials must be stored in hazardous material storage cabinets complying with Section 5003.8.7; cabinets must not contain other storage (§ 6603.1.2.1, § 6603.1.2.5). Some displays and Group S/M storage follow Section 5003.11 exceptions.

Table — Quick decision‑matrix (numeric thresholds and referenced code)

Decision factor	Key value / action	Code Reference
MAQ per control area	See Section 5003.1 / Table 5003.1.1 — consult table for numeric MAQ	§ 6603.1, § 6703.1
Indoor pile max (unstable / water‑reactive)	500 cubic feet per pile; separate into ≤500 cu ft piles if >500 cu ft	§ 6604.1.4, § 6704.1.5
Outdoor pile max (unstable)	1,000 cubic feet per pile	§ 6604.2.4
Indoor aisle width	≥ pile height or 4 ft, whichever greater	§ 6604.1.4, § 6704.1.5
Outdoor aisle width	≥ ½ pile height or 10 ft, whichever greater	§ 6604.2.5, § 6704.2.4
Outdoor separation (Class 1/2 unstable)	20 feet min (unless 2‑hr fire barrier)	§ 6604.2.3
Outdoor separation (Class 3 water‑reactive)	75 feet min	§ 6704.2.2
Explosion control required	Indoor Class 3/4 unstable; Class 2/3 water‑reactive — use Section 911 methods	§ 6604.1.2, § 6704.1.6
Liquid‑tight floors	Required for storage areas (liquid‑tight, noncombustible)	§ 6604.1.3, § 6704.1.2; see § 5004.12

Exceptions & special cases

Display/storage in Group M and storage in Group S may be allowed under § 5003.11 — see the exceptions in § 6601.1 and § 6701.1. Detonable unstable or water‑reactive materials are treated under Chapter 56 (explosives) or other special chapters.
Where the code refers you to tables (e.g., deflagration/detonation separation tables), follow the numeric values in those specific tables (Table 5604.5.2(2)/(3) for certain unstable classes) rather than using the general 20 ft / 75 ft rules. § 6604.2.1–6604.2.2.
Tanks are an exception to pile‑size rules: materials stored in tanks are not subject to the pile‑size separation exception in some sections — see the “Exception: Materials stored in tanks” language in § 6604.1.4 and § 6704.1.5.

Common mistakes

Relying on memory for MAQ numbers instead of checking Table 5003.1.1 (the code repeatedly ties chapter compliance to that Table). § 6603.1, § 6703.1.
Storing Class 3/4 unstable materials in prohibited occupancies (Group R, offices, retail) — see § 6603.1.2.x.
Forgetting liquid‑tight floors and watertight containers for water‑reactives and storage rooms (required by § 6704.1.2–.4).
Mixing water‑reactive Class 2/3 with flammable liquids (expressly prohibited — § 6704.1.5).
Ignoring explosion control (Section 911) where required — for example indoor Class 3/4 unstable and Class 2/3 water‑reactive require engineered explosion control measures.

Worked example — concrete scenario with numbers

Scenario: A research lab wishes to store 800 cubic feet of a Class 2 unstable (reactive) solid indoors.

Step 1 — Check control‑area MAQ:

First, check Table 5003.1.1 (Section 5003.1) to determine the MAQ per control area for Class 2 unstable. If the lab’s 800 cu ft is below that MAQ, normal storage rules apply; if 800 cu ft exceeds the MAQ, treat the storage as exceeding the MAQ and follow Chapter 50 + Chapter 66. (I do not have the Table 5003.1.1 numeric MAQ in the retrieved files — consult the code or AHJ.)

Step 2 — Apply pile / aisle rules (code‑backed):

Because the quantity is greater than 500 cubic feet, separate into piles each not larger than 500 cubic feet per § 6604.1.4. Practical approach: split into two piles (500 cu ft and 300 cu ft).

Step 3 — Aisle width:

Provide an aisle width between piles equal to the height of the piles or 4 feet, whichever is greater (per § 6604.1.4). If piles are 6 feet high, aisles must be at least 6 feet.

Step 4 — Other indoor requirements:

Ensure liquid‑tight floors in the storage area (§ 6604.1.3). If the stored class calls for explosion control (Class 2 may or may not — check classification), provide explosion control per Section 911 if required by the class language in Chapter 66. Confirm occupancy allowances (e.g., not in a prohibited occupancy per § 6603.1.2).

Summary: Splitting the 800 cu ft into piles ≤500 cu ft and meeting aisle, floor, and explosion control rules satisfies the physical configuration requirements in § 6604; whether additional measures are needed depends on the MAQ in Section 5003.1 and Chapter 50 filing/engineering requirements.

Related provisions (quick reference)

§ 6601 — General (scope, permits) for unstable (reactive) materials.
§ 6603 — General requirements; occupancy limits; link to Section 5003.1 (MAQ).
§ 6604 — Storage requirements for unstable (reactive) materials (indoor/outdoor, piles, distances, floors, explosion control).
§ 6701 — General (scope, permits) for water‑reactive solids and liquids.
§ 6704 — Storage requirements for water‑reactive solids and liquids (watertight containers, waterproof rooms, piles, distances, explosion control).
Section 5003.1 / Table 5003.1.1 — Maximum allowable quantities per control area (the primary source of MAQ values referenced by Chapters 66/67). (See § 6603.1, § 6703.1.)
Section 5003.8.7 — Hazardous material storage cabinet requirements referenced for laboratories and classrooms (used in § 6603.1.2.x).
Section 5004.12 — Liquid‑tight floor provisions referenced by § 6604.1.3 / § 6704.1.2.
Section 911 — Explosion control methods referenced by §§ 6604.1.2 and 6704.1.6.

Code references

Grounded in the retrieved California Fire Code — click a citation to read the verbatim passage:

CFC § 6603.1.2.2 High relevance — show source text
1. The hazardous material storage cabinets shall not contain other storage.
6603.1.2.2 Group R occupancies. Class 3 and 4 unstable (reactive) materials shall not be stored or used within Group R occupancies.

6603.1.2.3 Group M occupancies. Class 4 unstable (reactive) materials shall not be stored or used in retail sales portions of Group M occupancies.

6603.1.2.4 Offices. Class 3 and 4 unstable (reactive) materials shall not be stored or used in offices of Group B, F, M or S occupancies.

6603.1.2.5 Classrooms. In classrooms in Group B, F or M occupancies, any amount of Class 3 and 4 unstable (reactive) materials shall be stored in accordance with the following:
1. Class 3 and 4 unstable (reactive) materials shall be stored in hazardous material storage cabinets complying with Section 5003.8.7.
2. The hazardous material storage cabinets shall not contain other storage.
6603.2 Quantities exceeding the maximum allowable quantity per control area. The storage and use of unstable (reactive) materials in amounts exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Chapter 50 and this chapter.

2025 CALIFORNIA FIRE CODE 66-3

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

UNSTABLE (REACTIVE) MATERIALS

SECTION 6604—STORAGE

6604.1 Indoor storage. Indoor storage of unstable (reactive) materials in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(1) shall be in accordance with Sections 5001, 5003, 5004 and this chapter.

In addition, Class 3 and 4 unstable (reactive) detonable materials shall be stored in accordance with the California Building Code requirements for explosives.

6604.1.1 Detached storage. Storage of unstable (reactive) materials shall be in detached buildings where required in Section 5003.8.2.

6604.1.2 Explosion control. Indoor storage rooms, areas and buildings containing Class 3 or 4 unstable (reactive) materials shall be provided with explosion control in accordance with Section 911.

6604.1.3 Liquid-tight floor. In addition to Section 5004.12, floors of storage areas for liquids and solids shall be of liquid-tight construction.

6604.1.4 Storage configuration. Unstable (reactive) materials stored in quantities greater than 500 cubic feet (14 m [3] ) shall be separated into piles, each not larger than 500 cubic feet (14 m [3] ). Aisle width shall be not less than the height of the piles or 4 feet (1219 mm), whichever is greater.

Exception: Materials stored in tanks.

6604.1.5 Location in building. Unstable (reactive) materials shall not be stored in basements.

6604.2 Outdoor storage. Outdoor storage of unstable (reactive) materials in amounts exceeding the maximum allowable quantities per control area indicated in Table 5003.1.1(3) shall be in accordance with Sections 5001, 5003, 5004 and this chapter.

CFC § 6604.2.4 High relevance — show source text

** Outdoor storage of Class 2 or 1 unstable (reactive) materials shall not be located within 20 feet (6096 mm) of buildings not associated with the manufacture or distribution of such materials, lot lines, public streets, public alleys, public ways or means of egress. The minimum required distance shall not apply where fire barriers without openings or penetrations having a minimum fire-resistance rating of 2 hours interrupt the line of sight between the storage and the exposure. The fire barrier shall either be an independent structure or the exterior wall of the building adjacent to the storage area. 6604.2.4 Storage configuration. Piles of unstable (reactive) materials shall not exceed 1,000 cubic feet (28 m [3] ).

6604.2.5 Aisle widths. Aisle widths between piles shall be not less than one-half the height of the pile or 10 feet (3048 mm), whichever is greater.

SECTION 6605—USE

6605.1 General. The use of unstable (reactive) materials in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(1) or 5003.1.1(3) shall be in accordance with Sections 5001, 5003, 5005 and this chapter.

66-4 2025 CALIFORNIA FIRE CODE

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CALIFORNIA FIRE CODE – MATRIX ADOPTION TABLE

CHAPTER 67 – WATER-REACTIVE SOLIDS AND LIQUIDS

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting Agency	BSC	BSC- CG	SFM	Col5	HCD	Col7	Col8	DSA	Col10	OSHPD	Col12	Col13	Col14	Col15	Col16	BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	T-24	T-19*	1	2	1/AC	AC	SS	1	1R	2	3	4	5	5	5	5	5	5	5	5	5
Adopt Entire Chapter			X
Adopt Entire Chapter as amended (amended sections listed below)
Adopt only those sections that are listed below
[California Code of Regulations, Title 19, Division 1]
Chapter / Section

CFC § 6601.1 High relevance — show source text
emergency.

SECTION 6601—GENERAL

6601.1 Scope. The storage and use of unstable (reactive) materials shall be in accordance with this chapter. Compressed gases shall also comply with Chapter 53.

Exceptions:
1. Display and storage in Group M and storage in Group S occupancies complying with Section 5003.11.
2. Detonable unstable (reactive) materials shall be stored in accordance with Chapter 56.
6601.2 Permits. Permits shall be required as set forth in Section 105.5.

SECTION 6602—DEFINITION

6602.1 Definition. The following term is defined in Chapter 2:

UNSTABLE (REACTIVE) MATERIAL.

Class 4.

Class 3.

Class 2.

Class 1.

SECTION 6603—GENERAL REQUIREMENTS

6603.1 Quantities not exceeding the maximum allowable quantity per control area. Quantities of unstable (reactive) materials not exceeding the maximum allowable quantity per control area shall be in accordance with Sections 6603.1.1 through 6603.1.2.5.

6603.1.1 General. The storage and use of unstable (reactive) materials in amounts not exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Sections 5001, 5003, 6601 and 6603.

6603.1.2 Limitations for indoor storage and use by occupancy. The indoor storage of unstable (reactive) materials shall be in accordance with Sections 6603.1.2.1 through 6603.1.2.5.

6603.1.2.1 Group A, E, I or U occupancies. In Group A, E, I or U occupancies, any amount of Class 3 and 4 unstable (reactive) materials shall be stored in accordance with the following:
1. Class 3 and 4 unstable (reactive) materials shall be stored in hazardous material storage cabinets complying with Section 5003.8.7.
2. The hazardous material storage cabinets shall not contain other storage.
6603.1.2.2 Group R occupancies. Class 3 and 4 unstable (reactive) materials shall not be stored or used within Group R occupancies.

6603.1.2.3 Group M occupancies. Class 4 unstable (reactive) materials shall not be stored or used in retail sales portions of Group M occupancies.

6603.1.2.4 Offices. Class 3 and 4 unstable (reactive) materials shall not be stored or used in offices of Group B, F, M or S occupancies.

6603.1.2.5 Classrooms. In classrooms in Group B, F or M occupancies, any amount of Class 3 and 4 unstable (reactive) materials shall be stored in accordance with the following:
1. Class 3 and 4 unstable (reactive) materials shall be stored in hazardous material storage cabinets complying with Section 5003.8.7.
2. The hazardous material storage cabinets shall not contain other storage.
6603.2 Quantities exceeding the maximum allowable quantity per control area. The storage and use of unstable (reactive) materials in amounts exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Chapter 50 and this chapter.

2025 CALIFORNIA FIRE CODE 66-3
CFC § 6604.2.2 High relevance — show source text
6604.2.2 Distance from storage to exposures Class 3 (deflagratable) materials. Outdoor storage of deflagratable Class 3 unstable (reactive) materials shall be in accordance with Table 5604.5.2(3). The number of pounds of material listed shall be the net weight of the material present.

6604.2.3 Distance from storage to exposures Class 2 and 1 materials. Outdoor storage of Class 2 or 1 unstable (reactive) materials shall not be located within 20 feet (6096 mm) of buildings not associated with the manufacture or distribution of such materials, lot lines, public streets, public alleys, public ways or means of egress. The minimum required distance shall not apply where fire barriers without openings or penetrations having a minimum fire-resistance rating of 2 hours interrupt the line of sight between the storage and the exposure. The fire barrier shall either be an independent structure or the exterior wall of the building adjacent to the storage area. 6604.2.4 Storage configuration. Piles of unstable (reactive) materials shall not exceed 1,000 cubic feet (28 m [3] ).

6604.2.5 Aisle widths. Aisle widths between piles shall be not less than one-half the height of the pile or 10 feet (3048 mm), whichever is greater.

SECTION 6605—USE

6605.1 General. The use of unstable (reactive) materials in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(1) or 5003.1.1(3) shall be in accordance with Sections 5001, 5003, 5005 and this chapter.

66-4 2025 CALIFORNIA FIRE CODE

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

CALIFORNIA FIRE CODE – MATRIX ADOPTION TABLE

CHAPTER 67 – WATER-REACTIVE SOLIDS AND LIQUIDS

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
CFC § 6604.1.1 High relevance — show source text
In addition, Class 3 and 4 unstable (reactive) detonable materials shall be stored in accordance with the California Building Code requirements for explosives.

6604.1.1 Detached storage. Storage of unstable (reactive) materials shall be in detached buildings where required in Section 5003.8.2.

6604.1.2 Explosion control. Indoor storage rooms, areas and buildings containing Class 3 or 4 unstable (reactive) materials shall be provided with explosion control in accordance with Section 911.

6604.1.3 Liquid-tight floor. In addition to Section 5004.12, floors of storage areas for liquids and solids shall be of liquid-tight construction.

6604.1.4 Storage configuration. Unstable (reactive) materials stored in quantities greater than 500 cubic feet (14 m [3] ) shall be separated into piles, each not larger than 500 cubic feet (14 m [3] ). Aisle width shall be not less than the height of the piles or 4 feet (1219 mm), whichever is greater.

Exception: Materials stored in tanks.

6604.1.5 Location in building. Unstable (reactive) materials shall not be stored in basements.

6604.2 Outdoor storage. Outdoor storage of unstable (reactive) materials in amounts exceeding the maximum allowable quantities per control area indicated in Table 5003.1.1(3) shall be in accordance with Sections 5001, 5003, 5004 and this chapter.

6604.2.1 Distance from storage to exposures Class 4 and 3 (detonable) materials. Outdoor storage of Class 4 or 3 (detonable) unstable (reactive) material shall be in accordance with Table 5604.5.2(2). The number of pounds of material listed in the table shall be the net weight of the material present. Alternatively, the number of pounds of material shall be based on a trinitrotoluene (TNT) equivalent weight.

6604.2.2 Distance from storage to exposures Class 3 (deflagratable) materials. Outdoor storage of deflagratable Class 3 unstable (reactive) materials shall be in accordance with Table 5604.5.2(3). The number of pounds of material listed shall be the net weight of the material present.

6604.2.3 Distance from storage to exposures Class 2 and 1 materials. Outdoor storage of Class 2 or 1 unstable (reactive) materials shall not be located within 20 feet (6096 mm) of buildings not associated with the manufacture or distribution of such materials, lot lines, public streets, public alleys, public ways or means of egress. The minimum required distance shall not apply where fire barriers without openings or penetrations having a minimum fire-resistance rating of 2 hours interrupt the line of sight between the storage and the exposure. The fire barrier shall either be an independent structure or the exterior wall of the building adjacent to the storage area. 6604.2.4 Storage configuration. Piles of unstable (reactive) materials shall not exceed 1,000 cubic feet (28 m [3] ).

6604.2.5 Aisle widths. Aisle widths between piles shall be not less than one-half the height of the pile or 10 feet (3048 mm), whichever is greater.

SECTION 6605—USE
CFC § 0.25 High relevance — show source text
g|0|0| |Unstable
(reactive)|4|H-1|1e, g|(1)e, g|10e, g|0.25g|(0.25)g|2e, g|0.25g|(0.25)g| |Unstable
(reactive)|3|H-1 or H-2|5d, e|(5)d, e|50d, e|1d|(1)d|10d, e|1d|(1)d| |Unstable
(reactive)|2|H-3|50d, e|(50)d, e|750d, e|50d|(50)d|750d, e|10d|(10)d| |Unstable
(reactive)|1|NA|NL|NL|NL|NL|NL|NL|NL|NL| |Water reactive|3|H-2|5d, e|(5)d, e|NA|5d|(5)d|NA|1d|(1)d| |Water reactive|2|H-3|50d, e|(50)d, e|(50)d, e|50d|(50)d|(50)d|10d|(10)d| |Water reactive|1|NA|NL|NL|NL|NL|NL|NL|NL|NL| |For SI: 1 cubic foot = 0.028 m3, 1 pound = 0.454 kg, 1 gallon = 3.785 L.
NL = Not Limited; NA = Not Applicable; UD = Unclassified Detonable.
a. For use of control areas, see Section 414.2.
b. The aggregate quantity in use and storage shall not exceed the maximum allowable quantity for storage, including applicable increases.
c._ Reserved.
d.** [SFM]** In other than Group L occupancies,maximum allowable quantities shall be increased 100 percent in buildings equipped throughout with an automatic sprinkler system
in accordance with Section 903.3.1.1. Where Note e also applies, the increase for both notes shall be applied accumulatively.
e. Maximum allowable quantities shall be increased 100 percent when stored in approved storage cabinets, day boxes, gas cabinets, gas rooms or exhausted enclosures or in
listed safety cans in accordance with Section 5003.9.10 of the_California Fire Code. Where Note d also applies, the increase for both notes shall be applied accumulatively.
f. Quantities shall not be limited in a building equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1.
g. Allowed only in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1.
h. Containing not more than the maximum allowable quantity per control area of Class IA, IB or IC flammable liquids.
i. Quantities in parentheses indicate quantity units in parentheses at the head of each column.
j. A maximum quantity of 220 pounds of solid or 22 gallons of liquid Class 3 oxidizers is allowed when such materials are necessary for maintenance purposes, operation or sani-
tation of equipment when the storage containers and the manner of storage are approved.
k. Net weight of the pyrotechnic composition of the fireworks. Where the net weight of the pyrotechnic composition of the fireworks is not known, 25 percent of the gross weight
of the fireworks, including packaging, shall be used.
l.
CFC § 0.02832 High relevance — show source text
e|1d|(1)d|10d, e|1d|(1)d| |Unstable
(reactive)|2|H-3|50d, e|(50)d, e|750d, e|50d|(50)d|750d, e|10d|(10)d| |Unstable
(reactive)|1|NA|NL|NL|NL|NL|NL|NL|NL|NL| |Water
reactive|3|H-2|5d, e|(5)d, e|NA|5d|(5)d|NA|1d|(1)d| |Water
reactive|2|H-3|50d, e|(50)d, e|(50)d, e|50d|(50)d|(50)d|10d|(10)d| |Water
reactive|1|NA|NL|NL|NL|NL|NL|NL|NL|NL| |For SI: 1 cubic foot = 0.02832 m3, 1 pound = 0.454 kg, 1 gallon = 3.785 L.
NA = Not Applicable, NL = Not Limited, UD = Unclassified Detonable.
a. For use of control areas, see Section 5003.8.3.
b. The aggregate quantity in use and storage shall not exceed the maximum allowance quantity for storage, including applicable increases.
c. For hazardous materials in Group B higher education laboratory occupancies, see Section 428 of the_California Building Code_ and Chapter 38.
d._ [SFM]__ In other than Group L occupancies, maximum allowable quantities shall be increased 100 percent in buildings equipped throughout with an automatic sprinkler system in_
accordance with Section 903.3.1.1. Where Note e also applies, the increase for both notes shall be applied accumulatively. For Group L occupancies, refer to California Building
Code Table 453.7.2.1 for approved cabinets.
e. Maximum allowable quantities shall be increased 100 percent where stored in approved storage cabinets, day boxes, gas cabinets, gas rooms, exhausted enclosures or in
listed safety cans in accordance with Section 5003.9.10. Where Note d applies, the increase for both notes shall be applied accumulatively.
f. Quantities shall not be limited in a building equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1.
g. Allowed only in buildings equipped throughout with an approved automatic sprinkler system.
h. Containing not more than the maximum allowable quantity per control area of Class IA, Class IB or Class IC flammable liquids.
i. Quantities in parentheses indicate quantity units in parentheses at the head of each column.
j. A maximum quantity of 220 pounds of solid or 22 gallons of liquid Class 3 oxidizers is allowed where such materials are necessary for maintenance purposes, operation or
sanitation of equipment where the storage containers and the manner of storage are approved.
k. Net weight of pyrotechnic composition of the fireworks. Where the net weight of the pyrotechnic composition of the fireworks is not known, 25 percent of the gross weight of
the fireworks including packaging shall be used.
l. For gallons of liquids, divide the amount in pounds by 10 in accordance with Section 5003.1.2.
m.For oxidizers, unstable (reactive) materials and water-reactive materials stored or displayed in Group M occupancies or stored in Group S occupancies, see Section 5003.11.
n.
CFC § 1.11. High relevance — show source text
- The California Code of Regulations (CCR), Title 19, Division 1 provisions that are found in the California Fire Code are a reprint from the current CCR, Title 19, Division 1 text for the code user’s convenience only. The scope, applicability and appeals procedures of CCR, Title 19, Division I remain the same. The state agency does not adopt sections identified by the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.
2025 CALIFORNIA FIRE CODE 66-1

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66-2 2025 CALIFORNIA FIRE CODE

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66 UNSTABLE (REACTIVE) MATERIALS

User notes:

About this chapter: Chapter 66 addresses the hazards of unstable (reactive) liquid and solid materials as well as unstable (reactive) compressed gases. In addition to their unstable reactivity, these materials may pose other hazards, such as toxicity, corrosivity, explosivity, flammability or oxidizing potential. This chapter, however, is intended to address those materials whose primary hazard is unstable reactivity. Materials that pose multiple hazards must conform to the requirements of the code with respect to all hazards. Strict compliance with the provisions of this chapter, along with proper housekeeping and storage arrangements, helps to reduce the exposure hazards associated with unstable (reactive) materials in a fire or other

emergency.

SECTION 6601—GENERAL

6601.1 Scope. The storage and use of unstable (reactive) materials shall be in accordance with this chapter. Compressed gases shall also comply with Chapter 53.

Exceptions:
1. Display and storage in Group M and storage in Group S occupancies complying with Section 5003.11.
2. Detonable unstable (reactive) materials shall be stored in accordance with Chapter 56.
6601.2 Permits. Permits shall be required as set forth in Section 105.5.

SECTION 6602—DEFINITION

6602.1 Definition. The following term is defined in Chapter 2:

UNSTABLE (REACTIVE) MATERIAL.

Class 4.

Class 3.

Class 2.

Class 1.

SECTION 6603—GENERAL REQUIREMENTS

6603.1 Quantities not exceeding the maximum allowable quantity per control area. Quantities of unstable (reactive) materials not exceeding the maximum allowable quantity per control area shall be in accordance with Sections 6603.1.1 through 6603.1.2.5.

6603.1.1 General. The storage and use of unstable (reactive) materials in amounts not exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Sections 5001, 5003, 6601 and 6603.

6603.1.2 Limitations for indoor storage and use by occupancy. The indoor storage of unstable (reactive) materials shall be in accordance with Sections 6603.1.2.1 through 6603.1.2.5.
CFC § 4-43 High relevance — show source text
2025 CALIFORNIA BUILDING CODE 4-43

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SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY AND USE

[F] 415.8.1 Multiple hazards. Group H-2 or H-3 occupancies containing materials that are in themselves both physical and health hazards in quantities exceeding the maximum allowable quantities per control area in Table 307.1(2) shall comply with requirements for Group H-2, H-3 or H-4 occupancies as applicable.

[F] 415.8.2 Separation of incompatible materials. Hazardous materials other than those specified in Table 415.6.5 shall be allowed in manufacturing, processing, dispensing, use or storage areas when separated from incompatible materials in accordance with the provisions of the California Fire Code .

[F] 415.8.3 Water reactives. Group H-2 and H-3 occupancies containing water-reactive materials shall be resistant to water penetration. Piping for conveying liquids shall not be over or through areas containing water reactives, unless isolated by approved liquid-tight construction.

Exception: Fire protection piping shall be permitted over or through areas containing water reactives without isolating it with liquid-tight construction.

[F] 415.8.4 Floors in storage rooms. Floors in storage areas for organic peroxides, oxidizers, pyrophoric materials, unstable (reactive) materials and water-reactive solids and liquids shall be of liquid-tight, noncombustible construction.

[F] 415.8.5 Waterproof room. Rooms or areas used for the storage of water-reactive solids and liquids shall be constructed in a manner that resists the penetration of water through the use of waterproof materials. Piping carrying water for other than approved automatic sprinkler systems shall not be within such rooms or areas.

[F] 415.9 Group H-2. Occupancies in Group H-2 shall be constructed in accordance with Sections 415.9.1 through 415.9.3 and the California Fire Code.

[F] 415.9.1 Flammable and combustible liquids. The storage, handling, processing and transporting of flammable and combustible liquids in Group H-2 and H-3 occupancies shall be in accordance with Sections 415.9.1.1 through 415.9.1.9, the California Mechanical Code and the California Fire Code .

[F] 415.9.1.1 Mixed occupancies. Where the storage tank area is located in a building of two or more occupancies and the quantity of liquid exceeds the maximum allowable quantity for one control area, the use shall be completely separated from adjacent occupancies in accordance with the requirements of Section 508.4.

[F] 415.9.1.1.1 Height exception. Where storage tanks are located within a building not more than one story above grade plane, the height limitation of Section 504 shall not apply for Group H.

[F] 415.9.1.2 Tank protection. Storage tanks shall be noncombustible and protected from physical damage. Fire barriers or horizontal assemblies or both around the storage tanks shall be permitted as the method of protection from physical damage.

[F] 415.9.1.3 Tanks. Storage tanks shall be approved tanks conforming to the requirements of the California Fire Code .
CFC § 67-1 High relevance — show source text
2025 CALIFORNIA FIRE CODE 67-1

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67-2 2025 CALIFORNIA FIRE CODE

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67 WATER-REACTIVE SOLIDS AND LIQUIDS

User notes:

About this chapter: Chapter 67 addresses the hazards associated with water-reactive materials that are solid or liquid at normal temperatures and pressures. In addition to their water reactivity, these materials may pose a wide range of other hazards, such as toxicity, flammability, corrosiveness or oxidizing potential. This chapter addresses only those materials whose primary hazard is water reactivity. Materials that pose multiple hazards must conform to the requirements of this code with respect to all hazards. Strict compliance with the requirements of this chapter, along with proper housekeeping and storage arrangements, helps to reduce the exposure to hazards associated with water-reactive materials in a fire or other emergency.

SECTION 6701—GENERAL

6701.1 Scope. The storage and use of water-reactive solids and liquids shall be in accordance with this chapter.

Exceptions:
1. Display and storage in Group M and storage in Group S occupancies complying with Section 5003.11.
2. Detonable water-reactive solids and liquids shall be stored in accordance with Chapter 56.
6701.2 Permits. Permits shall be required as set forth in Section 105.5.

SECTION 6702—DEFINITION

6702.1 Definition. The following term is defined in Chapter 2:

WATER-REACTIVE MATERIAL.

Class 3.

Class 2.

Class 1.

SECTION 6703—GENERAL REQUIREMENTS

6703.1 Quantities not exceeding the maximum allowable quantity per control area. The storage and use of water-reactive solids and liquids in amounts not exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Sections 5001, 5003, 6701 and 6703.

6703.2 Quantities exceeding the maximum allowable quantity per control area. The storage and use of water-reactive solids and liquids in amounts exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Chapter 50 and this chapter.

SECTION 6704—STORAGE

6704.1 Indoor storage. Indoor storage of water-reactive solids and liquids in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(1), shall be in accordance with Sections 5001, 5003, 5004 and this chapter.

6704.1.1 Detached storage. Storage of water-reactive solids and liquids shall be in detached buildings where required by Section 5003.8.2.

6704.1.2 Liquid-tight floor. In addition to the provisions of Section 5004.12, floors in storage areas for water-reactive solids and liquids shall be of liquid-tight construction.

6704.1.3 Waterproof room. Rooms or areas used for the storage of water-reactive solids and liquids shall be constructed in a manner that resists the penetration of water through the use of waterproof materials. Piping carrying water for other than approved automatic sprinkler systems shall not be within such rooms or areas.
CFC § 6703.1 Medium relevance — show source text
WATER-REACTIVE MATERIAL.

Class 3.

Class 2.

Class 1.

SECTION 6703—GENERAL REQUIREMENTS

6703.1 Quantities not exceeding the maximum allowable quantity per control area. The storage and use of water-reactive solids and liquids in amounts not exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Sections 5001, 5003, 6701 and 6703.

6703.2 Quantities exceeding the maximum allowable quantity per control area. The storage and use of water-reactive solids and liquids in amounts exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Chapter 50 and this chapter.

SECTION 6704—STORAGE

6704.1 Indoor storage. Indoor storage of water-reactive solids and liquids in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(1), shall be in accordance with Sections 5001, 5003, 5004 and this chapter.

6704.1.1 Detached storage. Storage of water-reactive solids and liquids shall be in detached buildings where required by Section 5003.8.2.

6704.1.2 Liquid-tight floor. In addition to the provisions of Section 5004.12, floors in storage areas for water-reactive solids and liquids shall be of liquid-tight construction.

6704.1.3 Waterproof room. Rooms or areas used for the storage of water-reactive solids and liquids shall be constructed in a manner that resists the penetration of water through the use of waterproof materials. Piping carrying water for other than approved automatic sprinkler systems shall not be within such rooms or areas.

6704.1.4 Watertight containers. Where Class 3 water-reactive solids and liquids are stored in areas equipped with an automatic sprinkler system, the materials shall be stored in closed watertight containers. 6704.1.5 Storage configuration. Water-reactive solids and liquids stored in quantities greater than 500 cubic feet (14 m [3] ) shall be separated into piles, each not larger than 500 cubic feet (14 m [3] ). Aisle widths between piles shall be not less than the height of the pile or 4 feet (1219 mm), whichever is greater.

Exception: Water-reactive solids and liquids stored in tanks.

Class 2 water-reactive solids and liquids shall not be stored in basements unless such materials are stored in closed watertight containers or tanks.

Class 3 water-reactive solids and liquids shall not be stored in basements.

Class 2 or 3 water-reactive solids and liquids shall not be stored with flammable liquids.

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WATER-REACTIVE SOLIDS AND LIQUIDS

6704.1.6 Explosion control. Indoor storage rooms, areas and buildings containing Class 2 or 3 water-reactive solids and liquids shall be provided with explosion control in accordance with Section 911.

6704.2 Outdoor storage. Outdoor storage of water-reactive solids and liquids in quantities exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(3) shall be in accordance with Sections 5001, 5003, 5004 and this chapter.

CFC § 4-40 Medium relevance — show source text

4-40 2025 CALIFORNIA BUILDING CODE

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SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY AND USE

[F] TABLE 414.5.1—EXPLOSION CONTROL REQUIREMENTSa, h—continued	Col2	Col3	Col4
MATERIAL	CLASS	EXPLOSION CONTROL METHODS	EXPLOSION CONTROL METHODS
MATERIAL	CLASS	Barricade construction	Explosion (deflagration) venting or explosion (deflagration) prevention systemsb
Oxidizer liquids and solids	4	Required	Not Permitted
Pyrophoric gas	—	Not Required	Required
Unstable (reactive)	4	Required	Not Permitted
Unstable (reactive)	3 Detonable	Required	Not Permitted
Unstable (reactive)	3 Nondetonable	Not Required	Required
Water-reactive liquids and solids	3	Not Required	Required
Water-reactive liquids and solids	2g	Not Required	Required
SPECIAL USES
Acetylene generator rooms	—	Not Required	Required
Electrochemical energy storage systemi	—	Not Required	Required
Energy storage systemi	—	Not Required	Required
Grain processing	—	Not Required	Required
Liquefied petroleum gas-distri- bution facilities	—	Not Required	Required
Where explosion hazards existf	Detonation	Required	Not Permitted
Where explosion hazards existf	Deflagration	Not Required	Required
a. See Section 414.1.3. b. See the_California Fire Code_. c. Combustible dusts where manufactured, generated or used in such a manner that the concentration and conditions create a fire or explosion hazard based on information prepared in accordance with Section 104.2.2 of the_California Fire Code_. See definition of "Combustible dust" in Chapter 2. d. Storage or use. e. In open use or dispensing. f. Rooms containing dispensing and use of hazardous materials where an explosive environment can occur because of the characteristics or nature of the hazardous materials or as a result of the dispensing or use process. g. A method of explosion control shall be provided where Class 2 water-reactive materials can form potentially explosive mixtures. h. Explosion venting is not required for Group H-5 fabrication areas complying with Section 415.11.1 and the_California Fire Code_. i. Where explosion control is required in Section 1207 of the_California Fire Code_. j. Does not apply to consumer fireworks, Division 1.4G. k. Not required for Category 1B Flammable Gases having a burning velocity not exceeding 3.9 inches per second (10 cm/s).	a. See Section 414.1.3. b. See the_California Fire Code_. c. Combustible dusts where manufactured, generated or used in such a manner that the concentration and conditions create a fire or explosion hazard based on information prepared in accordance with Section 104.2.2 of the_California Fire Code_. See definition of "Combustible dust" in Chapter 2. d.

Frequently asked questions

What is the first thing I must check before deciding storage rules for these materials?

Check the maximum allowable quantity (MAQ) per control area in Section 5003.1 / Table 5003.1.1. If your planned quantity exceeds the MAQ, Chapters 50 and 66/67 impose additional engineering, separation, and permitting requirements.

Can I store Class 3 or 4 unstable materials in an office or a residence?

No. Class 3 and 4 unstable materials are prohibited in Group R occupancies and are prohibited in ordinary offices (Groups B, F, M, S) per § 6603.1.2.2–.4.

Do water‑reactive materials need special containers?

Yes — Class 3 water‑reactive solids and liquids stored in areas with sprinklers must be in closed watertight containers; rooms must be waterproof and piping conveying water (except sprinklers) is restricted. § 6704.1.3–.4.

What pile size and aisle width do I need indoors?

If storage exceeds 500 cubic feet, separate into piles that are no larger than 500 cubic feet; aisles must be at least the height of the piles or 4 feet, whichever is greater (§ 6604.1.4 / § 6704.1.5).

Who enforces these limits and do I need a permit?

Local fire code officials enforce the CFC provisions; permits are required as set out in Section 105.5 and the permit requirements are referenced in § 6601.2 and § 6701.2. Consult your local authority having jurisdiction (AHJ).

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California Fire Code