The Deadly Hazards of Indoor Marijuana Grow Houses

Illegal marijuana growing ­facilities (IMGF) pose numerous long- and short-term health effects to fire, police, and emergency medical services (EMS) personnel. At first glance, you may consider a grow house similar to a common greenhouse. IMGFs usually contain numerous hazards that can kill you instantly or initiate a long, slow death if you are exposed and unaware. The purpose of this article is to familiarize you with the hazards of IMGFs so you can recognize and safely operate and simultaneously protect your crew and citizens. Let’s look at a typical response.

The Call

The electric supply house driver was delivering a package of high-intensity lightbulbs and called in the alarm. The fire department is dispatched for a house fire and burn victim. The home is a typical high ranch home on a large piece of property with a long driveway. The 30-year-old male victim is outside the garage door in the driveway, rolling around in obvious extreme pain and respiratory distress. One leg of his nylon pants is burned away, and the other is still smoldering. He appears to have third-degree burns to one leg and burns to his face and is in severe respiratory distress. There is a small fire just inside the basement through the door that leads from the garage.

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Your initial size-up makes you suspicious. The home is isolated, is not well kept, and has blacked-out windows on the A side. Some odd odors are coming from the open door from the garage to the basement that even may have drifted far enough to reach your command post. The first-due engine extinguished the fire using the first line and the apparatus tank water. Because of your suspicions, you order your crew not to overhaul. Since the fire was near the open door from the garage to the basement, the firefighters did not don their self-contained breathing apparatus (SCBA) face pieces. Two of your members are now experiencing nausea, shortness of breath, and headaches.

(1) Photos courtesy of Miami-Dade (FL) Fire Rescue.

(1) Photos courtesy of Miami-Dade (FL) Fire Rescue.

As the crew is knocking down the fire, a police officer approaches the command post and advises you that for the past two months, a local narcotics unit has been collecting intelligence and gathering enough probable cause to execute a search warrant; they believe the house is a significantly large and sophisticated IMGF. The grow operation is believed to be on the first floor and in the basement of the residence.

A grow operation may have plants in pots filled with soil or it may be a hydroponic type where plants are fed with nutrients via water systems. Let’s look into the details to understand the hazards the first-in engine faces and how to protect responding personnel.

The Victim

The victim was burned while he was extracting tetrahydrocannabinol (THC) from the marijuana plants using a flammable solvent. THC is an intermediary chemical compound in the marijuana or cannabis plant that causes the euphoric high. It is extracted in an oil form and added to a marijuana cigarette or placed into a marijuana pipe and smoked. Smoking is the only way, besides a pill form, that marijuana is taken into the body. Oil from one plant can bring as much as $3,500 from addicts. Common components for this process to look for in your size-up include casserole dishes, coffee filters, bicycle pumps, and cans of butane.

To extract the THC from the plant, the entire plant is ground up and placed in an extraction tube. A solvent such as butane is dripped through the marijuana inside the extraction tube. The final step is to remove the solvent by treating it with a heat source.

The Fire

The victim was burned when the heavier-than-air butane vapors pooled near the floor and found an ignition source, likely the pilot light on the hot water heater or the furnace. The flammable range for butane is 1.8 to 8.5 percent in air. The butane fire raced back along the floor until it reached the victim. Since his clothes were saturated with vapors, rapid fire involvement ensued. The synthetic sweatpants burned, melted, and stuck to his skin in several areas. The butane fire caused the victim’s burns that concurrently compromised his respiratory system. Once the bulk of the butane flash fire was consumed, only small pockets of fire remained for the fire department. The delivery driver must have come on the scene very soon after the initial fire and made his 911 call. Let’s examine the additional hazards of this alarm.

IMGF Indicators

Often, there will be many unique, unimaginable hazards such as booby traps, heavy door security, and window bars not found in a typical residence. For firefighters, the complicating factor is they may be well-hidden. For camouflage, houses may be well-kept with apparently normal residents. Because of the lucrative nature of marijuana sales, sometimes only a part of the home may be dedicated to grow operations. Vigilance during your size-up for clues of a grow house will help keep you and your crew safe. Indications of a possible grow house include the following:

    • Windows that are blacked out, are boarded up from the interior, or have heavy curtains that prevent responders from making a reliable size-up and that contain smoke to hide the fire.
    • To conceal any odor from the growing plants, doors and windows may be sealed with plastic. Odors may be vented through the plumbing vent system or unusual roof vents. Odors from grow houses are unique and pungent.
    • Look for unusually heavy electrical connections necessary to support the lighting and ventilation systems. Law enforcement often uses electric meter readings as an intelligence-gathering tool.
    • Beware of structural compromise before the fire: structural weakness caused by illegal conversion from residence to IMGF.
    • Insulation can hide structural weaknesses (trusses, joists), which have been modified to run piping, venting, air-conditioning, or heating pipes and flexible ductwork. Often, this is in the form of foil-backed foam board. In cooler climates, it reduces heating costs and, in warmer climates, air-conditioning costs. In all cases, it helps provide camouflage for the operation for law enforcement and during our size-up. The reflective surface will interfere with successful use of our thermal imaging cameras (photo 2).
      The Deadly Hazards of Indoor Marijuana Grow Houses

Common IMGF Hazards

Electrical. All plants need light to grow. Legal greenhouses will have clear glass to let in the light. Illegal grow houses must be clandestine, and so windows are usually covered on the inside. High-intensity grow lamps make up for the loss of sunlight, which often creates the following electrical hazards:

    • The huge electric demand may overload breaker panels and common household circuits, creating typical fire hazards and ignition sources.
    • Electric meters are often bypassed to conceal the heavy energy consumption, which would make the utility billing office suspicious.
    • Wiring for this heavy-duty electric service is usually shabby and less than code compliant (photo 1). However, some well-funded grow houses have excellent and robust wiring systems. Nonetheless, the process still needs large amounts of electricity. Look for unusually heavy wiring feeding the home during your size-up.
    • Many high-intensity lights require ballasts, which, if not appropriate for the light fixture, the voltage, and so forth, can create a hazard. Lights and ballasts can remain very hot even after they are shut down, so allow time for them to cool if you have to enter the facility.
    • Water is a simple but universally present hazard that often complicates the “electrician’s nightmare” of wiring. Since plants need water, drums or other containers of water are left open in the grow house. Some may contain diluted fertilizer that is applied to the plants manually or through an automated drip irrigation system. During a fire and in dense smoke, knocking over a large container of water onto wires laid along the floor could be deadly for the entire fire crew.
    • Redundantly verify that the electricity is off. Even if you have carried out normal procedures (e.g., pulling electric meters, disconnecting generators), verify there is no electricity present before entry and especially before dismantling or fire department overhaul. Since electric service is often being stolen, there is a unique hazard of buried electric lines from nearby homes that may be feeding the illegal grow house.

Chemical and airborne hazards: carbon dioxide (CO2) and carbon monoxide (CO). Humans breathe in air containing oxygen and exhale air containing reduced oxygen and some CO2. Plants use CO2 in the photosynthesis process and produce oxygen. To stimulate plant growth, high levels of CO2 may be released into the IMGH from compressed gas cylinders. Obviously, this can exclude oxygen-creating scenarios similar to those we see at restaurants that have leaking CO2 soda systems. Some illegal cultivators also confuse CO with CO2 and will vent from the home’s furnace into the grow area and accidentally introduce high levels into the environment. CO is flammable at concentrations of 12.5 to 74 percent. Growers may have compressed gas cylinders of CO2 and a distribution system to encourage plant growth. Monitor the air for increased toxic gas concentrations and lower oxygen that is displaced.

An alternative to compressed CO2 cylinders is a propane or natural gas-fired CO2 generator. Coupled with unsafe installation and use, there is an obvious potential for natural gas or propane explosions. On September 27, 2016, Fire Department of New York Battalion Chief Michael Fahy was killed in a building explosion while directing operations at a gas leak incident in the Bronx. The structure was alleged to contain a marijuana grow house, likely fueled by natural gas.

Flammable solvents. As previously mentioned, they are used to extract THC from the plants. In addition to butane, ethanol, alcohol, acetone, ether, and naphtha may be used or stored in significant quantities and pose unusual flammability and explosion hazards not associated with a typical house fire. In 2014, California firefighters responded to a fire in an IMGF and found several thousand burned butane canisters along with nearly 2,000 full canisters that did not catch fire. Captain Siegfried Klein of the Aurora (CO) Fire and Explosives Investigation Bureau documented the flammability and fire hazards at the 2016 Fire Department Instructors Conference and in the Fire Engineering March 2016 issue.

Herbicides/pesticides/rodenticides/fungicides. These deadly chemicals are all designed to kill some living organism. Many cultivators will mix some or all of these chemicals to save time, creating a toxic soup that can vary widely. Chemical reactions caused by unknown quantities and concentrations mixed in the unique IMGF environment may cause the containers to off-gas dangerously. Combined with limited ventilation, this witch’s brew may have dermal and respiratory exposure routes, producing short-term and long-term health effects.

Mold. Mold and fungus grow in the moist, warm, and fertile environment of the IMGF. Typically, fire, police, and EMS personnel do not recognize this as a hazard because they are not trained to. Airborne spores (mold and fungus seeds) are invisible to the naked eye, are very buoyant, drift on air currents, and can be inhaled easily if respiratory protection is not used. Additionally, mold and fungus grow in dark, damp areas that may not be easily observed, such as under tables where plants are growing.

It is important to note that in recent years there have been numerous incidents where law enforcement personnel have fallen ill long after and immediately after exposure to IMGF. A few days after eradicating approximately 1,000 marijuana plants from an IMGF, a Denver police officer developed severe back pain. Exploratory surgery found white fungus between the vertebrae in his spine. The bacteria and fungus were identified as Diptheroid-type bacteria and an Aspergillums species fungus.

In another case, a police officer processed a small IMGF. The next morning, he developed a sore throat and a cough. Over time, the cough developed into shortness of breath. It was determined his symptoms were consistent with a reaction to mold exposure. Long-term health effects may follow these short-term symptoms.

Pharmacology of Cannabis


The term marijuana refers to the leaves, stems, and dried flower buds of the Cannibas plant of which there are three types: Cannibas Sativa, Cannabis Indica, and Cannabis Ruderalis. The terms cannibas, marijuana, and marihuana are often used interchangeably. Since the 1840s, pharmaceutical companies have used cannibas in medicines to treat migraines, insomnia, and arthritis conditions resulting in poor appetite. For centuries, cannabis has been used for recreational purposes. In many countries and now in several states in the United States, cannabis is perceived as a harmless recreational drug.

The primary psychoactive component of cannabis is delta 9-tetrahydrocannabinol (THC), which produces a variety of effects in humans and animals. These effects typically include euphoria, relaxation, and an altered perception of time. Concentration and learning are also often impaired while using cannabis. Physiological effects can include significant changes in heart rate, diastolic blood pressure, dry mouth, increased appetite, and decreased respiratory rate. Although it is used as a recreational drug, it can lead to dependence, and heavy users are more prone to psychiatric disorders. Unfortunately, there is very limited research on the chronic effects of cannabis.

Cannabis is metabolized in the liver, slightly more slowly in women than in men, and considerably more quickly in chronic users. More than 65 percent of cannabis is secreted in the feces and 20 percent in the urine, most of it over five days following use. Although urine is preferred in drug testing because of the higher concentration, drug testing can use saliva, blood, urine, hair, and fingernails or toenails.

MIKE McEVOY, PhD, NRP, RN, CCRN, is the EMS coordinator for Saratoga County, New York; the EMS technical editor for Fire Engineering; and a member of the JEMS educational editorial board. He’s a nurse clinician in the cardiac surgical ICU at Albany (NY) Medical Center, where he also chairs the resuscitation committee and teaches critical care medicine. He’s the chief medical officer and a paramedic/firefighter for the West Crescent (NY) Fire Department.

Hazard Mitigation Considerations

Following are some considerations to help improve efficiency and protect responders at an IMGF.

Unified command. Because of the complex, unique, and unpredictable hazards, a team (fire, police, and EMS) effort is required to ensure the safety of all responders. Expertise and information will have to be shared equally among fire, police, and EMS units. Because of the variety of hazards typically found in an IMGF, additional experts such as building and fire inspectors and utility crews may be required to evaluate hazards and ensure the safety of ongoing operations. Unified command is a necessity.

Police often do not want to divulge any information to the fire department or others about current IMGF surveillance to protect the investigation and the future criminal case. Surprises are not good in any emergency services discipline. If possible, police leadership should share some of this critical information with fire department leaders in that response area to prevent firefighter injuries at a known or suspected IMGF.

Personnel safety. First-in police, fire, and EMS personnel along with the delivery man in the above incident may have been exposed to some or all of the hazards. First-responding police officers assisting early in the call may also be exposed or contaminated. EMS personnel may have been contaminated or exposed to any contaminants the victim may have had on his person or clothing. Recall that early in the response, this appears to be a burn victim at a typical residence. It will take some time to determine whether it is an IMGF.

Clearly, command will shift from the fire department to the police department, but a unified and cooperative atmosphere must prevail from the initial operation until successful completion. This includes the conclusion of the investigation and dismantling of the IMGF. Consider gross decontamination of personnel at the scene early in the operation.

Assisting agencies and law enforcement. The local narcotics unit may not be trained or equipped to investigate and dismantle the complex hazards of an IMGF. Often, the state police clandestine drug lab enforcement team or the U.S. Drug Enforcement Agency clandestine lab investigation teams are better staffed, trained, and equipped for this mission than local law enforcement. Conducting the investigation and evidence collection under IMGF conditions is a unique law enforcement challenge. State police units often have the experience and expertise required.

Electric hazards. Because of the risk of electrocution while dismantling an IMGF, the state police team will likely request that the local utility company respond to shut down all power at the residence. Also, the local fire department was requested to be on the scene because of the danger of explosion or fire posed by the THC extraction lab.

Grow lights. After the utility company has confirmed that all power has been shut off, allow cooling time for the lighting and ballasts. High-intensity grow lights can generate up to 100°F to 125°F and will have a surface temperature of more than 500°F; the ballast can hold a charge for up to 45 minutes. These lights may be similar to metal halide or high-pressure sodium lights you may find in a gymnasium. Damaged or shoddy wiring can also provide ignition sources until they are shut down.

Flammable atmospheres. Consider using intrinsically safe radios and flashlights when in any environment where you find large amounts of solvents and possible explosive atmospheres. The New York State Police often tape a four-gas meter to the ankles of first-in team members to check for low-lying flammable gases.

Personal protective equipment (PPE) selection. Follow normal requirements based on the specifics of the situation. However, realize that the overall appearance of the IMGF may obscure the hazards previously noted. Electrical and construction hazards may be obvious, but serious health threats of airborne contaminants may be well disguised, posing a threat to unprotected responders.

Decontamination. Investigations and evidence collection take time, especially in a contaminated environment. Obviously, both emergency decon and technical decon are required for investigator/entry team safety. Keep the fire department and a local hazmat team on scene for emergency decon and for technical decon on exiting the hot zone. Evidence containers and tools used may need a thorough decon as well.

The Rockland County (NY) Hazmat Team has made it a practice of requesting the fire department to provide a hoseline near where the entry team is operating. The entry team can use this line to provide immediate emergency decon for severely contaminated or injured entry personnel without what may be a long walk from the hot zone to the formal technical decon station. This single hoseline does not replace a full decon line but provides immediate relief for entry team members.

Incident Termination

Although the emergency phase of this operation is over, law enforcement has two critical and continuing operations to terminate the incident, evidence collection and dismantling of the IMGF. Both require support from the fire department/hazmat team. This may develop as follows.

The local law enforcement/narcotics team/unit requested the state police clandestine drug lab enforcement team to assist because of the numerous hazards present in the crime scene and the need to collect evidence in a contaminated environment. An initial briefing was held with these team leaders, local narcotics unit members, the fire department, and other agencies described above. A situation report on what was discovered subsequent to the fire and a plan was developed to make initial entry to survey the IMGF.

Initial PPE determination, like any other hazmat call, depends on site conditions. In this case, what your gas meter displays will drive your PPE selection. The flammable gas/liquid hazard may be the most serious, so first entry PPE would be more fire resistive than chemical hazard driven. Since the survey team is inside and not disturbing the chemical hazards, rule out the most dangerous hazard first, probably fire/explosion, then transition to specific PPE for chemical hazards during the dismantling operation.

Based on the specifics of the IMGF, the damage or destruction by the fire, and investigative information, initial entry team PPE may range from level C to level A. In this case, the lab team sent two members wearing level B PPE into the home to conduct an initial survey and assess the grow operation and to monitor the atmosphere using a four-gas meter with a photo ionization detector (PID) to monitor the oxygen, CO, CO2 lower explosive limits, and any possible volatile organic compounds. The PID also detects many contaminants at lower levels than the typical four-gas sensors will.

The initial entry is a risk-based entry, strictly to determine what, if any, hazards still remain and to gain information to modify and fill out details for the evidence collection and dismantling plans. Since a THC extraction lab was located, the site safety officer had the entry team members upgrade to PPE to protect against liquid-chemical splash and flash fire because the use of numerous solvents in the THC extraction process increased the hazards of a fire. Local fire department and hazmat team leaders were part of the unified command and provided support for emergency and technical decon.

The state police team collected evidence and turned it over to local law enforcement for processing and to develop charges for the cultivators. The IMGF was dismantled by removing and destroying the plants, securing the utilities, and removing the hazardous wastes (by a certified contractor).

News reports from across the country, especially those from states where marijuana has been legalized, provide numerous examples of IMGFs that have challenged first responders with explosions, heavy fire, and the unseen hazards noted above. Consider them in your size-up at every fire.

Authors’ note: Thanks to Chief Wayne Melton, Orange County (NY) Hazmat, and Captain Bill Gustin, Miami-Dade (FL) Fire-Rescue, for their assistance with this article.

References “Thousands Attend Funeral of FDNY Battalion Chief.” October 1, 2016.

Gustin, Bill. “Dangers of Grow Houses.” Fire Engineering, June 2010.

Hansen, Jamie. “Lake County blaze leads to discovery of honey oil lab.” The Press Democrat, March 25, 2014.

Klein, Siegfried. “Butane Hash Oil Manufacturing: It’s a Fire Service Problem, Too.” Fire Engineering, March 2016.

NIOSH Pocket Guide to Chemical Hazards. U.S. Centers for Disease Control and Prevention, September 2007.

SHAWNE MAILE is an investigator with the New York State Police Contaminated Crime Scene Emergency Response Team and has been involved in narcotic investigations for 14 years, with a specialty in investigating and processing clandestine drug laboratories and indoor marijuana grow operations. He is a state police instructor for clandestine drug labs and marijuana grows and has lectured on these topics to more than 80 federal, state, and local law enforcement and first responder agencies. He has been featured in training articles and lectures for the U.S. Drug Enforcement Administration, U.S. Customs and Border Protection, and Fire Department of New York. He is a certified New York State hazardous materials technician.

JERRY KNAPP is a 40-year veteran firefighter/EMT with the West Haverstraw (NY) Fire Department and a training officer at the Rockland County Fire Training Center in Pomona, New York. He has a degree in fire protection and is the chief of the Rockland County Hazmat Team and a former paramedic. He is the author of the Fire Attack chapter in Fire Engineering’s Handbook for Firefighter I and II, the reference book House Fires, and numerous articles for Fire Engineering. He is on the technical panel for the latest Underwriters Laboratories study on fire attack at house fires and recently retired from the U.S. Military Academy, West Point, as the plans officer, Directorate of Emergency Services.

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