With the surge of interest in retail marijuana products, it’s important to understand the hazards associated with cannabis cultivation and extraction. If unchecked, these processes can become dangerous. Poor practices result in serious injury and death. Most incidents occur in makeshift laboratories, when hazardous contents ignite and cause a fire or explosion. Yet, cannabis production should not be feared. When a marijuana facility is properly designed and cognizant of its hazards, it’s no more dangerous than any other industrial occupancy using hazardous contents.
Understanding the processes in a marijuana facility is the first step in identifying and preventing hazardous conditions. Cannabis is a genus of flowering plant. Its species are used for industrial, medical, and recreational purposes. Like all plants, it uses carbon dioxide (CO2), light and water to grow. Once grown, cannabis is cultivated and used in raw form or refined through extraction processes to create cannabis oil (also known as hash oil, honey oil, etc.).
To create cannabis oil, a solvent (butane, ethanol, isopropanol, propane, etc.) is used to draw tetrahydrocannabinol (THC) from the flowers, leaves, and stems of marijuana plants. The resulting mixture of solvent and THC is then filtered and collected. Afterwards, the mixture is heated to evaporate the solvent and acquire the desired oil.
Outside of normal life safety concerns, the followings topics must be analyzed when designing a facility for cultivation and extraction:
- Location of hazards,
- Quantity of hazardous contents, and
- Operational procedures.
Plants are susceptible to fire, and thus present a moderate hazard throughout the grow rooms. Additionally, they use fertilizers and CO2 to grow. Fertilizers are potentially explosive, and CO2 is an asphyxiate.
One of the main components in manufactured fertilizers is ammonium nitrate. Manufacturer’s use it because it’s a great macronutrient and it’s cheap to produce. However, with a high enough activation energy (from fires, shock waves, etc.), it explodes. Therefore, it’s worth considering options that don’t include ammonium nitrate.
CO2 displaces oxygen (O2). At higher levels, a person experiences difficulties breathing, nausea, loss of consciousness, and death. The earth’s atmosphere contains approximately .04% by volume. Cultivation facilities use CO2 dispersion systems to replace that which is absorbed by plants. These systems must be monitored to ensure safe levels of CO2. Per the Occupational Safety and Health Administration (OSHA 29 CFR 1910.1000), the permissible exposure limit (PEL) for CO2 is 5,000 parts per million (PPM) over an 8-hour work day. This is equivalent to .5% by volume. If this limit is reached, the dispersion system must be automatically turned off.
As mentioned, the extraction process involves the use of solvents. Liquids can be classified as flammable or combustible per their boiling temperatures and flashpoints. These liquids don’t burn. It’s the mixture of their vapors and environmental O2 that ignite. In general, flammable liquids release ignitable vapors at normal working temperatures. Combustible liquids release ignitable vapors once heated.
When conducting the extraction process, it’s important to create and adhere to an approved standard of operation. To reduce the risk of spills, solvents should be used in closed containers (such as screw-top jugs and squirt bottles) whenever possible. If not in use, these containers should be in a liquid storage room or a fire cabinet.
Various codes govern the maximum allowable amount of hazardous materials in control areas. In the State of New Hampshire, these codes include, but are not limited to, the International Building Code (IBC), the Fire Code (NFPA 1) and the Flammable and Combustible Liquids Code (NFPA 30). If exceeded, a use group becomes classified as high hazard and must comply with stringent and very expensive requirements. Therefore, it’s important to regulate the amount of hazardous materials on site.
A liquid storage room allows the greatest amounts of hazardous contents to be stored. However, the room must comply with applicable codes. It must be separated from the remainder of the facility by hourly fire rated construction. It also must safeguard against the release of flammable vapors and spills. To protect against the release of flammable vapors, a gas detector monitors hazardous content levels. To protect against spills, liquid storage rooms include containment or drainage to a location that’s separate from local waterways. If using containment, the size of the pit must consider the volume of stored liquids, as well as runoff from the required sprinkler system. Sprinkler systems must meet the requirements of the most hazardous contents in storage. When designing a sprinkler system, it’s good to locate an indicating valve outside of the liquid storage room. This gives firefighters the option to control the flow of water to the protected space. Electrically, the room must comply with Class 1, Division 2 requirements. Ordinary plug-in outlets are prohibited in these environments.
Ventilation is crucial when performing an extraction. To ignite, a vapor air mixture cannot be too lean or too rich. Therefore, to prevent ignition, vapors should be maintained below their lower flammability limit (LFL). NFPA defines the LFL as the concentration of a flammable vapor in air below which ignition will not occur. It’s also known as the lower explosive limit (LEL). To maintain appropriate levels of hazardous vapors, extractions should be conducted in a fume extractor with appropriate flow and filtering capacity. In ductless extractors, solvents are separated from the air by activated carbon filters. Generally, these filters extract up to 25-33% of their weight, before becoming saturated. Logically, larger filters have longer life cycles (assuming the filters are used at the same intensity). To know when a filter needs replacing, an indicator should be used. An indicator can be as simple as a sticker changing color.
In closing, cannabis production should not be feared. When designing a marijuana facility, it’s important to accompany a safe layout with proper protocol. These combine to mitigate hazards from cultivation and extraction. As the legalization of marijuana becomes widespread, it’s becoming increasingly important to understand the processes of cultivation and extraction, to properly identify and prevent hazardous conditions.
Written By: Mark R. Richards, PE