ArticleEquipment to manage fumigation, CO2 enrichment, high intensity lighting, large volume humidity control, and oil extraction are commonplace in industrial facilities and are becoming increasingly common in burgeoning marijuana grow and processing facilities.
The legalization of marijuana in Washington, Colorado, and other states has created a market for the growth of marijuana that has seen its share of fires, explosions, code violations and other mishaps as amateur growers and entrepreneurs attempt to transition into large commercial facilities operators.
In this article, mechanical engineer, Bruce Straughan, P.E. covers some of the equipment and processes that are present in marijuana grow and processing facilities and discusses the potential consequences that can arise if they are not managed in a professional manner.
Due to changes in the laws of certain states in the last several years, there has been a dramatic increase in the number of facilities used in the United States for the cultivation, processing, and retail selling of marijuana. This article provides an overview of the equipment typically installed in these facilities, their operation, and applicable building codes and standards.
The Legal Landscape
As of 2017, eight states and the District of Columbia have passed laws legalizing marijuana for recreational use, and a total of 29 states have legalized it for medical use. Although these laws provide for the cultivation, processing, and retail selling of marijuana to be regulated at the state level, these activities remain illegal under federal law. The U.S. Department of Justice has stated its policy on drug enforcement priorities, and they include preventing revenue from the sale of marijuana from going to criminal enterprises, preventing the diversion of marijuana from states where it is legal under state law to other states, and preventing state-authorized marijuana activity from being used as a cover for other illegal drugs or illegal activity. Outside of its stated enforcement priorities, however, the federal government has traditionally relied on state and local authorities to address marijuana activity through enforcement of their own laws. Although, some federal drug raids of facilities that were legal under state law have occurred, they have been rare. And the marijuana industry has continued to flourish. According to a report in the New York Times, legal sales of marijuana in the U.S. amounted to $6.6 billion in 2016 and are projected to grow by 16% annually and reach $24 billion by 2025.
The Anatomy of a Grow Facility
In decades past, marijuana was grown mainly outdoors. Indoor grow rooms utilizing high intensity lamps offer many advantages to the grower, including better security, protection from bad weather, protection from outdoor contaminants and pests, and the ability to control the environment to ideal temperature, humidity, and air quality conditions. This control ability allows for greatly increased crop yields.Commercial grow facilities will typically contain the following systems and equipment:
- High intensity lamps
- Heating, air conditioning, and humidity control equipment
- Ventilation fans
- Fans to circulate air around the room
- CO2 emitting equipment
- Irrigation system
- Chemicals for fertilizer and pesticides
- Fire protection system
- Security systems
- Computerized control system to monitor the environment and operate the equipment to maintain optimum conditions to maximize the crop yield.
Codes and Standards – Managing the Hazards
Building permits and inspections by local building officials are required for all legal commercial marijuana operations regardless of whether the facility is a new building project or a remodel to an existing building. As long as marijuana facilities are designed, constructed, and operated according to applicable codes and standards, the risk of harm to people inside the facility and the surrounding areas is greatly mitigated. But the various systems in a facility do warrant consideration of any potential hazards, and proper installation and operating procedures must be carefully followed. An improperly designed, constructed and operated facility can also cause damage to the property or the product.
Without natural light, grow rooms depend on grow lights which need to replicate the parts of the sunlight spectrum that the marijuana plants need at each stage of growth. High-pressure sodium lamps are a type of high intensity lamp that has become popular for grow rooms, and 1000 watt bulbs are often selected. These lamps have a high electrical demand and emit a great deal of heat. If these lamps are located too close to combustible materials, fires can occur. Grow lights may be turned off at night and the duration of the lights out period can be gradually altered to simulate the changing seasons and trigger plants to enter the flowering stage.
The rate of photosynthesis of plants is greatly affected by the concentration of CO2 in the air in the room. CO2 enrichment systems are typically in the form of a compressed CO2 gas cylinder or a natural gas burner that emits products of combustion into the room. Under normal operation, room CO2 is maintained at an elevated level (1500 ppm) but well below hazardous levels and with safety controls, alarms, and warning signs. Either system type presents potential asphyxiation hazards if not properly controlled. The fuel-fired type also presents a CO hazard and is regulated by the International Fuel Gas Code (IFGC) as a non-vented fuel-fired appliance, requiring an oxygen depletion sensor interlocked with an exhaust fan.
Fumigation is regulated by fire codes and typically requires an operational permit. Common methods of fumigation include CO2 to control pests and sulfur burners used to control mildew. CO2 can be used for fumigation at levels above OSHA’s immediately dangerous to life or health level (IDLH) of 40,000 ppm. Sulfur burners create sulfur dioxide, which can burn the respiratory tract if inhaled. Any type of fumigation is a concern to anyone entering the space, such as employees or first responders entering in the event of a fire. Adjacent tenants or bystanders could also be at risk if the chemicals were to leak from the space.
Ventilation systems are important for removing contaminants from the space and also help with keeping the space cool. Marijuana plants emit a very strong “skunk like” odor, and local authorities typically require ventilation systems to be installed such that any odors are prevented from leaving the premises. This is usually accomplished by installing a charcoal filter on the discharge of the exhaust duct. Other methods to reduce odors include ozone generators and ionizers.
Due to the high heat output of the grow lamps, indoor grow facilities require air conditioning. Marijuana plants grow best at temperatures in the range of 68 to 72 degrees F, and heating equipment is also needed to maintain this optimal temperature range. The optimum humidity range is about 50% to 60% relative humidity. Growing plants transpire a significant amount of water vapor and will cause the air in the room to become very humid if not controlled. During times when the grow lights are on, the dehumidifying effect of the air conditioning unit will typically keep the humidity levels within an acceptable range. When the lights are off, however, a separate dehumidification unit or a reheat coil in the air conditioning system are typically needed. In order to maximize the rate of plant growth, humidity levels must be kept in the optimum range. If the humidity gets excessively high, the grow room becomes a conducive environment for the growth of mold and pathogenic organisms. The walls and ceiling construction of the room should include vapor barriers and corrosion resistant materials. The walls should have sufficient insulation behind the vapor barrier to minimize the chances of moisture in the air condensing and forming water droplets on the wall.
Grow facilities are classified under the International Building Code (IBC) as an F-1 Occupancy, Factory Industrial, Moderate Hazard. If the floor area of the facility exceeds 12,000 sq. ft., then a fire sprinkler system is required. IBC also requires fire walls with a one-hour separation between the facility and any adjacent occupancy as well as wall and ceiling finishes with a flame spread index within the limits specified in the code. Means of Egress as required in IBC, Chapter 10 is an important consideration for the facility. Marijuana grow facilities do not normally use just a single large open room for growing. Plants that are at different stages of growth need to be isolated into separate groups due to their different lighting requirements. Many commercial grow facilities are converted warehouses and can be maze-like due to the added walls to create the multiple rooms that are needed. Care must be taken to ensure that egress paths are clear and do not become blocked by equipment or storage containers.
Grow rooms should be provided with floor drains to remove spilled water and nutrient solutions. The drains should be trapped and equipped with screens to catch any plant material or other debris. The International Plumbing Code requires that water supply lines used for irrigation purposes be provided with back-flow preventers to protect the domestic water supply from contamination.
Grow facilities have a very high electrical demand due to the grow lights, air conditioning units, and other equipment. The electrical system must be sized and installed in accordance with the National Electric Code (NEC). Fire Codes prohibit the use of extension cords or power strips as permanent wiring to equipment, lighting, fans, etc. Overloaded electrical wiring has caused fires in some marijuana grow facilities. In addition to ensuring that the electrical system inside the building is designed and installed properly, the electric service entry equipment and conductors for the building need to be evaluated. If the facility was created as a remodel to an existing building, it may be necessary for the electric utility company to upgrade the conductors and/or transformer serving the building.
Because the sale of marijuana is still illegal under federal law, most banks have not been willing to work with marijuana related businesses. This has made it difficult or impossible for facility operators to obtain banking services, forcing them to operate as all-cash businesses. Due to large sums of cash on hand in addition to marijuana inventory, security is a major concern for any marijuana facility, especially retail stores. Local codes can vary, but in some states, an alarm system and video surveillance system are required by law.
Processing Facilities for Marijuana Infused Products
Marijuana infused edible products such as brownies and candy are becoming more prevalent as an alternative to smoked marijuana. These products are typically infused with highly concentrated oil that is extracted from plant leaves and buds and is commonly known as “hash oil.” The extract oil can also be smoked or used in vapor cigarettes. There are several different methods used to extract the oil, and most methods use flammable solvents. Any legal extraction operation will draw close scrutiny from local building and fire code officials who will typically review the extraction process and issue a marijuana extraction operational permit to ensure it is done in compliance with the applicable codes.
Extraction using butane as a solvent is a cost effective method, but can be dangerous if codes are not followed. Fire codes prohibit open releases of butane to the atmosphere during the extraction process. Equipment is commercially available that cycles the butane around a closed-loop, totally enclosed system that passes the butane through the plant material. The butane, which is under pressure and in the liquid state, acts as a solvent and removes the oil from the plant. The butane is then recollected, and the extract oil can then be retrieved from a reservoir. Denver, Colorado was the first U.S. city to begin regulating the butane hash oil process as a commercial operation, and requires an engineering analysis, signed and sealed by a licensed professional engineer to be submitted for approval. The basis of the analysis is National Fire Protection Association (NFPA) 58, Liquefied Petroleum Gas Code. Businesses using this equipment are required to have a hazardous material exhaust system installed to capture any accidental release of butane, and a hydrocarbon detector to alert the operator of butane leaks. The exhaust fan is required to be connected to an emergency power system per the NEC. Depending on the quantity of butane used, the facility may be classified under IBC as a Group H, High Hazard Occupancy. Requiring closed systems and an equipment approval process is critical to ensure the extraction process is done safely. In 2014, there were 32 reported butane hash-oil explosions in Colorado alone, caused by using unapproved, open vent butane extraction methods. This method releases butane directly to the surrounding air with the user exposed to a cloud of flammable gas. Because this open system type extraction method can be used so cheaply, it has been used in both commercial and residential buildings.
CO2 extraction is a less common method for producing hash oil from marijuana. In Denver, the equipment must follow the same approval process as butane extraction equipment. Although there is no chemical explosion risk like there is with butane equipment, the systems can operate at pressures as high as 10,000 psi. Therefore, the equipment must be reviewed to ensure it is constructed properly. Businesses that use this type of equipment are required to perform the extraction in a dedicated room with a CO2 alarm to alert of leaks.
Another common extraction method is an alcohol distillation. Although alcohol or 190-proof liquor is the most common solvent used in this method, almost any flammable liquid can be used. Marijuana leaves and buds are soaked in the alcohol, and the liquid is then boiled off, leaving the oil behind. This type of process is required to comply with NFPA 30, Flammable and Combustible Liquids. A hazardous vapor exhaust hood is required to be installed over the extraction process equipment to capture any flammable vapors released. Equipment must be rated for heating flammable liquids, and open flames are prohibited.
Residential Facilities Pose Many Concerns
In 2015, a law went into effect in Colorado that prohibits the use of butane in residential buildings for extracting oil from marijuana plants. It is legal to cultivate plants inside residential buildings within certain limits as stated by law in some states. Oftentimes, lighting and equipment used in residential operations is not installed or operated according to code, and many concerns have arisen.
Electrical work is not always done with a building permit or done by licensed contractors. Unsafe electrical practices are common, including open wiring, inadequate fuses or circuit breakers, bad connections, and overloading of circuits, dramatically increasing the likelihood of fires and explosions. High intensity grow lamps can reach a surface temperature of 500 degrees F or higher and also pose a fire hazard.
Home based growers have been known to vent the exhaust from gas-fired appliances such as water heaters or furnaces directly into their grow rooms to provide CO2 enrichment. This is a blatant violation of mechanical codes and poses a risk of carbon monoxide poisoning.
The warm, humid environment ideal for plant growth is also conducive for the growth of mold. Since residential operations typically lack the robust humidity controls found in commercial operations, the likelihood of excessively high humidity levels is greatly increased. This can lead to property and product damage from mold on the walls and the structure and to the growth of pathogenic organisms on the product.
Crime related to residential operations is also a concern, with home invasions to steal crops, equipment, and cash known to occur. Laws typically limit the number of plants that can be cultivated by a single person to a small number. But the limit for a single house can be greatly increased by obtaining a doctor’s recommendation for medical marijuana and by multiple adults living in the same house.
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Bruce Straughan P.E., CEM
Mechanical Engineer & Building Systems Expert
This article was developed by Bruce Straughan with research support and peer review from other members of Robson Forensic’s building systems practice group. Bruce is a mechanical engineer with over 20 years of experience in the design, construction, and commissioning of building systems, including HVAC, plumbing, fire protection, smoke control, and cogeneration systems.
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