Appendix I — INDOOR HORTICULTURAL FACILITIES — 2025 California Mechanical Code (Title 24, Part 4)

(Matrix Adoption Tables are non-regulatory, 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	HCD			DSA			OSHPD							BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	SFM	1	2	1-AC	AC	SS	SS/CC	1	1R	2	3	4	5	6	6	6	6	6	6	6	6	6
Adopt Entire Chapter
Adopt Entire Chapter as amended (amended sections listed below)
Adopt only those sections that are listed below
Chapter/Section

This state agency does not adopt sections identified with 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 1.11.0.

554 2025 CALIFORNIA MECHANICAL CODE

APPENDIX I

INDOOR HORTICULTURAL FACILITIES The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in the adopting ordinance.

I 101.0 General.

I 101.1 Indoor Spaces. Indoor spaces using environmental controls for horticultural cultivation and processing of plants for human ingestion, inhalation, and topical application shall comply with this section.

Equipment and appliances shall be installed in accordance with the manufacturer’s installation instructions and

this code. Piping, tubing, materials, and structures shall be protected in accordance with Section 316.0.

I 101.2 Plumbing Systems. Indoor horticulture plumbing systems shall be in accordance with the plumbing code.

I 101.3 Mechanical Systems. Indoor horticulture mechanical systems shall be in accordance with this code.

I 101.4 Fire Suppression Systems. Fire suppression systems shall be in accordance with the building code and Section I 501.1.3.

I 201.0 Definitions.

I 201.1 General. For the purpose of this appendix, the following definitions shall apply:

Cultivation Room. A room of any size where plants are grown under controlled conditions. Also known as a grow

room.

Extraction Equipment. Equipment used to extract compounds, oils, extracts and proteins from plants. The processes include, but not limited to, the extraction by a solvent, desolventizing, and distillation of the solvent.

Extraction Equipment, Non-Volatile. Extraction equipment utilizing any solvent that is not considered volatile (i.e., carbon dioxide).

Extraction Equipment, Volatile. Extraction equipment utilizing any solvent that is considered flammable and hazardous (i.e., Butane, propane, hexene, or ethanol).

Gas Detection Control Units. A digital or analog controller that continuously monitors the presence of toxic, anoxic, and explosive gases in the ambient air to prevent the risks of explosion linked to such gases.

Horticulture Facility. A business, facility, or establishment where retail indoor horticulture is grown, cultivated, dried, extracted, weighed, packaged, or processed.

Indoor Horticulture. The cultivation and processing of floricultural and horticultural plants in an indoor space by controlling various interior environmental variables including, but not limited to, temperature, air quality, humidity, artificial lighting, nutrients, and carbon dioxide.

I 301.0 Classification of Facilities.

I 301.1 General. Facilities used for indoor horticultural cultivation and processing shall be in accordance with the applicable codes as mandated by the Authority Having Jurisdiction. I 301.2 Approved Locations. Facilities used for indoor horticultural cultivation and processing shall be located in accordance with the building code and the Authority Having Jurisdiction.

I 401.0 Documentation.

I 401.1 General. Documentation for permitting shall be provided in accordance with the requirements of Section 104.0 and the Authority Having Jurisdiction. The documentation shall show compliance with this section and other requirements in accordance with the Authority Having Jurisdiction.

I 501.0 Fire Protection.

I 501.1 General. Fire protection shall be provided for indoor horticultural facilities in accordance with the building code, fire code, Section I 501.1.1 through Section I 501.1.3, and the Authority Having Jurisdiction.

I 501.1.1 Smoke Detectors and Fire Alarms. Smoke detectors, heat detectors, and fire alarms shall be provided in accordance with NFPA 72 and shall provide visible and audible notification. Smoke detectors installed within ducts shall comply with UL 268. In spaces where smoke detectors cannot be utilized due to ambient conditions, approved automatic heat detectors shall be permitted in lieu of smoke detectors in accordance Section

I 501.1.2.

I 501.1.2 Heat Detectors. Where ambient conditions prohibit installation of smoke detectors, an automatic heat detector in accordance with UL 521 shall be permitted where approved by the Authority Having Jurisdiction.

I 501.1.3 Fire Suppression. Where fire suppression is required by the fire code, an automatic fire suppression system shall be provided within hoods, enclosures, and ductwork in accordance with one of the following:

(1) A carbon dioxide extinguishing system in accordance with NFPA 12.

(2) An automatic water sprinkler system in accordance with NFPA 13.

(3) A dry chemical extinguishing system in accordance with NFPA 17.

(4) A gaseous agent extinguishing system in accordance with NFPA 2001.

(5) A fire suppression system as approved by the Authority Having Jurisdiction.

APPENDIX I

I 601.0 Carbon Dioxide Detection System. I 601.1 General. A gas detection system shall be provided in indoor spaces using a carbon dioxide enrichment process, in indoor spaces where carbon dioxide containers or generating systems are located. The gas detection system shall activate audible alarms distinguishable from the fire alarm system and alarms with visual notification. Such alarms shall be calibrated for the types of fuels or gases used.

I 601.1.1 Listings. The gas detection control units shall comply with UL 864 or UL 2017. Gas detectors shall comply with UL 2075.

I 601.1.2 Carbon Dioxide Sensor Location. Carbon

dioxide sensors shall be located within the breathable zone between 4 feet (1219 mm) to 6 feet (1829 mm) above the finished floor.

I 601.1.3 Activation. Activation of the gas detection system shall be in accordance with Section I 601.1.3.1 through Section I 601.1.3.2.

I 601.1.3.1 Low-Level Activation. Upon detection of a carbon dioxide concentration of 5000 ppm, the following shall be automatically performed:

(1) Stop the flow of carbon dioxide to the supply piping system.

(2) Activate the mechanical purge ventilation sys tem.

(3) Activate an audible and visual supervisory alarm signal at an approved location within the facility.

I 601.1.3.2 High-Level Activation. Upon detection of a carbon dioxide concentration of 30 000 ppm, the following shall be automatically performed:

(1) Stop the flow of carbon dioxide to the supply piping system.

(2) Activate the mechanical purge ventilation sys tem.

(3) Activate audible and visual alarms inside and outside where the following exist:

(a) An indoor space using a carbon dioxide enrichment process

(b) Where carbon dioxide containers, generating systems are located. I 601.2 Carbon Dioxide Enrichment System. Indoor spaces using a carbon dioxide enrichment process shall have a mechanical purge ventilation system and shall independently exhaust directly to the exterior. The design, installation, and maintenance of carbon dioxide enrichment systems with more than 100 pounds (45.4 kg) of carbon dioxide, and carbon dioxide enrichment systems having a remote fill connection shall comply with Section I 601.2.1 through Section I 601.2.3. I 601.2.1 Carbon Dioxide Systems. Pressure relief, vent piping, fill indicators, fill connections, vent terminations, piping systems and the storage, use, and handling of the carbon dioxide shall be in accordance with this section and NFPA 55.

I 601.2.2 Carbon Dioxide Control. Indoor spaces using a carbon dioxide enrichment process shall be maintained with a negative pressure in relation to adjoining indoor spaces or with a positive pressure and intervening entrance/exit pressurization vestibules with the adjoining indoor spaces.

I 601.2.3 Carbon Dioxide Supply Piping. Carbon dioxide supply piping shall be in accordance with ASME B31.3.

I 701.0 Flammable Solvents.

I 701.1 General. Processes using flammable solvents shall be provided with a flammable gas detection system in accordance with the fire code. The flammable gas detection system shall be installed in accordance with the manufacturer’s

installation instructions and shall not be interlocked with other equipment. The flammable gas detection system shall be calibrated to detect gas levels of not more than 10 percent of the Lower Flammable Limit (LFL) and to activate audible and visual alarms of not more than 25 percent of the LFL.

I 701.2 Control Area. Pumps, motors, chemical fume hoods, equipment, and wiring in control areas and containment booths used for flammable solvent processing shall be as Class I/Division 1 location for potentially explosive gas and vapor Groups A, B, C, and D in accordance with NFPA 70. Containment booths shall be listed and labeled in accor dance with UL 1389.

I 701.3 Extraction Equipment. Extraction equipment using flammable solvents and located in an indoor space shall be listed for the intended use. Plant extraction booths shall comply with UL 1389. Extraction equipment using LPG, Butane or other volatile solvents shall be a closed-loop control system and shall comply with ASME BPVC Section VIII.1, ASME B31.3, and NFPA 58, as applicable.

I 801.0 Ventilation and Exhaust System.

I 801.1 General. The indoor air quality in indoor spaces using environmental controls for horticultural cultivation, and processing shall comply with Chapter 4 and Section I 801.1.1. The ventilation and exhaust system shall comply with Section I 801.1.2 through Section I 801.1.6. Indoor spaces used for horticultural cultivation shall have an independent ventilation system.

All mechanical ventilation and exhaust systems shall be tested, balanced, and operated to demonstrate to the owner or designated representative and Authority Having Jurisdiction that the installation and performance of the systems conform to design intent. All testing and balancing shall be performed by a technician certified by the Associated Air Balance Council (AABC), the National Environmental Balancing Bureau (NEBB), the Testing, Adjusting and Balancing Bureau (TABB), or other equivalent approved agencies.

I 801.1.1 Breathing Zone Outdoor Airflow Rate. The outdoor airflow required in the breathing zone ( V bz ) of the occupiable space or spaces in a ventilation zone

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APPENDIX I

shall be as shown in Table 402.1 and not less than the value determined in accordance with Equation I 801.1.1. Vbz = Rp - Pz + Ra - Az (Equation I 801.1.1)

Where:

Az = zone floor area, the net occupiable floor area of the ventilation zone, ft [2] .

Pz = zone population, the number of people in the ventilation zone during typical usage. Rp = outdoor airflow rate required per person (CFM/person) in accordance with the following, as applicable:

(1) 60 CFM/person for cultivation, production, and processing facilities or factories.

(2) 15 CFM/person for centers and dispensaries.

Ra = outdoor airflow rate required per unit area, 1 CFM/ft [2]

For SI Units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute =

0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s, 1 cubic foot per

minute per square foot = 5.08 [(L/s)/m [2] ]

Sample Calculation: Determine the outdoor airflow required in the breathing zone ( Vbz ) of an indoor space used for horticultural cultivation with an occupiable floor area of 800 square feet and a maximum of 5 people expected to occupy the zone.

Sample Solution: Vbz = Rp - Pz + Ra - Az Vbz = (60 CFM/person • 5 people) + (1 CFM • 800 SF) Vbz = 1100 CFM. The ventilation system shall be capable of providing not less than 1100 CFM of outdoor air.

I 801.1.2 Ventilation System Requirements. When activated by the gas detection system required by Section I 601.1, the mechanical purge ventilation system shall remain on until manually reset. The purge ventilation system ducting shall terminate outdoors in an approved location. The ventilation system shall be designed to operate at a negative pressure of 0.01 inches water column (0.002 kPa) in relation to the exhausted indoor space.

I 801.1.3 Ventilation for Indoor Cultivation and Storage Spaces. Indoor spaces used for horticultural cultivation and processing and storage shall be provided with ventilation in accordance with Section 402.2. Where

mechanical ventilation is provided, the systems shall be operational when the indoor space(s) are occupied. Air in indoor cultivation and storage spaces shall be classified as Class 2 Air in accordance with Section 403.9.2.

I 801.1.4 Exhaust Ventilation Rate. The exhaust and ventilation system required in this section shall not create a lesser standard of installation than prescribed by the

minimum safety standards adopted by the Authority Having Jurisdiction. Exhaust airflow shall be provided at not less than 0.2 CFM/ft [2] [1.02 (L/s)/m [2] ] of floor area. Exhaust air shall not be used as makeup air, recirculated air, or transfer air. Makeup air shall be provided for more than 150 CFM (70.8 L/s) exhaust. I 801.1.5 Exhaust System Requirements. An exhaust system shall be installed in accordance with Section 505.0 and the following requirements:

(1) Exhaust outlet location(s) in accordance with Section 502.2.3 for product conveying ducts as classified in Section 505.8.

(2) Exhaust air shall terminate directly to the outdoors and shall not be directed onto a public way.

(3) The exhaust inlet shall be not less than 12 inches (305 mm) above the finished floor.

(4) Chemical fume hoods shall be required for flammable solvent processing, shall be listed, and shall be installed in accordance with the manufacturer’s

installation instructions.

(5) Exhaust ducts shall be independent of all other exhaust systems.

(6) The exhaust rate shall be in accordance with the appliable occupancy category as shown in Table 403.7.

I 801.1.6 Automatic Shutoff. Automatic shutoff in air moving systems shall be provided in accordance with Section 609.0.

I 901.0 Particulate and Odor Control.

I 901.1 General. Particulates and odors from indoor horticultural cultivation and processing of plants for human ingestion, inhalation, and topical application shall be filtered and controlled so that it is not detectable above nuisance levels not exceeding applicable exposure limits at the exterior of the facility or at adjoining properties or as required by the Authority Having Jurisdiction. Odor control shall be required in the exhaust system and shall include, but not be limited to, one or more of the following types:

(1) Charcoal filters shall be installed on the discharge of all exhaust ducts and shall be installed in accordance with

the manufacturer’s installation instructions.

(2) Ozone generators shall be installed in all exhaust ducts to neutralize odor by oxidizing such odors with ozone.

(3) Ionizers shall be installed in accordance with the manufacturer’s installation instructions.

(4) Photo-catalytic oxidation shall be installed in accordance with the manufacturer’s installation instructions.

(5) Photo-hydroxyl oxidation shall be installed in accordance with the manufacturer’s installation instructions.

(6) Carbon filtration shall be installed in accordance with the manufacturer’s installation instructions.

(7) UV-C lights shall be installed in accordance with the manufacturer’s installation instructions.

APPENDIX I

(8) Where approved by the Authority Having Jurisdiction, a plume discharge termination method shall be permitted to be used for odor control. The exhaust fan of such a

system shall discharge exhaust air vertically into the outdoors. The plume heights shall be not less than 20 feet (6096 mm) above the nozzle. Escaping air at the nozzle shall be no less than 3000 feet per minute (15.2 m/s).

I 901.2 Filters. Where filters are used, the minimum filtration rate shall be in accordance with Equation I 901.2. The design airflow velocity across the face area of the chemical absorption filter(s) shall not exceed 350 feet per minute (1.8 m/s).

(Equation I 901.2)

Minimum Filtration Rate = (Room Volume)/3

I 1001.0 Duct Construction and Installation.

I 1001.1 General. Ducts shall be in accordance with Chapter 6 and SMACNA HVAC Duct Construction Standards –

Metal and Flexible. Exhaust ducts shall be accordance with

Section 506.0.

I 1101.0 Hydronic Systems.

I 1101.1 General. Hydronic systems used in indoor horticulture facilities shall be in accordance with Chapter 12 of this code or Chapter 4 the Uniform Solar, Hydronics and Geothermal Code (USHGC).

I 1201.0 Motors and Fans.

I 1201.1 General. Motors and fans used shall comply with the applicable requirements in Section 503.0.

I 1301.0 Storage of Chemicals.

I 1301.1 General. Storage of chemicals shall comply with the building code and fire code, and NFPA 58 for liquid petroleum gas and NFPA 400 for the storage, use and handling of hazardous materials. Hazardous, combustible, and flammable materials shall not be stored in cultivation rooms.

I 1401.0 Walls, Ceilings, and Floors.

I 1401.1 General. Walls, ceilings, and floors of indoor spaces used for horticultural cultivation shall be in accordance with the following requirements:

(1) Be of corrosion resistant materials.

(2) Include air and vapor barriers in accordance the building code.

(3) Be insulated in accordance with the building code.

(4) Concrete slab floors shall be permitted to be sealed below or above grade by a product approved the Authority Having Jurisdiction.

I 1501.0 Dehumidification and Humidification.

I 1501.1 General. Dehumidification and humidification shall be permitted to be accomplished by standalone dehumidifiers, humidifiers, desiccant wheels, or reheat coils.

I 1501.2 Protection. Plants shall not be stored or processed beneath pipes or mechanical equipment unless those areas are protected against leakage or condensation.

Exception: Piping used for fire suppression systems.

I 1601.0 Fumigation.

I 1601.1 General. Any horticultural growing facility that is fumigated shall comply with Section I 1601.1.1 through Section I 1601.1.2 and the Authority Having Jurisdiction.

I 1601.1.1 Sources of Ignition. Areas intended to be fumigated shall not contain any open flames or any other sources of ignition.

I 1601.1.2 Fumigation Activity. Areas intended for fumigation, repellant, pesticide, or insecticide fogging operation shall be clearly marked to indicate fumigation activity. Such areas intended for fumigation shall be continuously mechanically ventilated in accordance with Section I 801.0.

I 1701.0 Luminaires.

I 1701.1 General. Horticultural lighting equipment and systems used for indoor horticultural cultivation shall comply with UL 8800.

I 1801.0 UV and UV-C Devices.

I 1801.1 General. UV and UV-C devices installed in duct work shall be installed in accordance with NFPA 90A and

the manufacturer’s installation instructions.

I 1901.0 Signage.

I 1901.1 General. Caution or warning signs complying with NFPA 704 shall be provided at the entrance of the facility and/or indoor spaces identifying hazards such as flammables, asphyxiants, and toxics.

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CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE