Indoor Marijuana Cultivation (Grow House)

Guidance on the recognition, hazards, and response considerations for illicit indoor marijuana cultivations (IMC)

Overview

Indoor marijuana grow operations range from small-scale residential setups to large commercial facilities. This guideline is primarily intended for improvised grow operations in single and multi-family residences.

PHOTO: Iliict IMC including bars on the widows

Recognition

A distinctive “skunk” or “rotten cabbage-like” odor of marijuana emitting from the residence
Unusual sounds coming from inside the residence (these are caused by grow light ballasts and sound similar to the humming of a utility pole-mounted transformer)
Bright light emitting from cracks around windows and doors
Plastic sheeting, plant stocks, fertilizer bags, plastic piping and large amount of soil and pots observed in the trash
Large quantities of potting soil and lumber delivered to the residence
Condensation collecting on windows (caused by high humidity in grow rooms)
Blacked-out or heavily shaded windows that are never opened
Windows and doors that are fortified with security bars not in character with the neighborhood
Extra locks on doors or gates that normally wouldn’t require it
The absence of snow or frost on roofs as compared to similar homes or rooflines, (figure 9) caused by the heat produced from grow lights

Hazards

There are numerous hazards, including the presence of fertilizers and other chemicals, pressurized CO2 and propane cylinders, entanglement risks, structural modifications, overloaded electrical circuits and bypassed electrical meters.

Chemicals

Chemicals are frequently present in indoor grows.

Fertilizers,
Herbicides,
Pesticides
Fungicides
Carbon Dixoide cylinders
Carbon Dixoide generators
Sulfur burners

Sulfur Burner

Of particular concern is a device known as a sulfur burner (figure 2). This device utilizes a heating element to melt sulfur pellets, which in turn produces sulfur dioxide (SO2). The device heats sulfur to its vaporization temperature (around 140°C or 284°F), creating sulfur dioxide (SO₂) gas

SO2 functions as a topical fungicide to prevent powdery mildew from forming on the plants. SO2 released within an enclosed space presents a serious hazard. When SO2 combines with water, the reaction yields sulfuric acid (H2SO3). As our airway and lungs contain water, inhalation can result in internal chemical burns.

CO2 Generator

Also concerning is the presence of pressurized CO2 cylinders and propane-powered CO2 generators. Increased CO2 within these tightly sealed rooms can displace oxygen, leading to asphyxiation.

Some improvised CO2 generators can appear to be one-pot meth labs.

Entanglement Hazards

Numerous entanglement hazards exist. Among these are ventilation ducting, exposed electrical wiring, electrical cords, flexible plastic irrigation tubing, and rope (figure 3). Of particular concern is large-diameter flexible ducting, which is used in conjunction with inline ventilation fans for both intake and exhaust of air, heat and moisture from grow rooms (figure 4). This ducting, constructed of a lightweight aluminum foil laminate wrapped around small diameter helical wire, is notorious for entangling firefighters. Under fire conditions, the exterior sheathing burns/melts away, leaving the helical wire exposed. In a smoke-filled environment, these entanglement hazards can be difficult to detect.

Electrical Hazards

One of the most significant indoor grow-related hazards is the potential for electric shock. Due mainly to lighting needs, IMC residences use an astounding amount of electricity. Each high-pressure sodium/metal halide light uses between 500 and 1,000 watts each, with a typical residential grow containing anywhere from 10 to 40 overhead lights (figure 12). One of these homes can consume upwards of 10,000 to 12,000 kW hours of electricity per month, nearly 20 times average household use! In addition, electrical equipment may be poorly wired and the home’s circuits overloaded, leading to potential shock and fire ignition sources.

PHOTO: October 1, 2024, the Fairfield Police Department

Of great concern are bypassed electrical meters. Due to either fear of detection by electric utility company employees or in wanting to avoid paying high electricity bills, growers will bypass electrical meters. As a result, personnel at an IMC fire may secure electrical utilities only to discover there is still power to the residence. If responders make contact with exposed wiring or spray hose streams onto energized equipment, there is a risk of electrocution.

Response Considerations

Structure Fire Response

Some IMC are discovered as a result of a structure fire response.

Strategy Selection

If a IMC is suspected during size, the IC should consider if an offensive or defensive strategy is appropriate. In addition to standard structure fire size up considerations, the IC should consider

Is this an occupied or unoccupied structure?

Can electrical utilities be secured?

Have entanglement hazards been encountered?

As soon as evidence of IMC is observed, ensure that all responding personnel and the dispatch center are notified over the incident’s command and tactical channels.
• Broadcast an emergency alert tone notifying personnel of the hazards.
• Request the electrical utility company respond to verify the building’s power has been isolated.
• Using the above mentioned criteria, establish either an offensive or defensive strategy.
• Following fire knockdown, continue to wear SCBA during overhaul operations. Due to the presence of fertilizers, herbicides, pesticides and sulfur emitters, use SCBA to reduce inhalation exposures.
• Notify law enforcement for investigative follow up of possible criminal activity. Preserve related evidence and communicate your findings to fire investigators.

Request a HazMat team

HazMat Response Considerations

PPE Selection

Insulated electrical gloves

Air monitoring and detection

Monitor for SO2 (consider H2S cross sensitivity)

CO2 monitor

Pesticide testing

CO2

Locate and turn off generators

Sulfur generator

CO2 generators