Four Common Fire Hazards in Cannabis Operations

Drew Paris, PE, CFEI

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Aug 27, 2020

Cannabis fires and explosions have been occurring in grow houses and processing facilities for decades. In the past, most of these facilities were operating illegally and weren’t built or maintained to common electrical and fire safety standards. Unfortunately, the lessons learned from these investigations were not well publicized and applied broadly throughout the industry. However, given the legalization of cannabis in many parts of the U.S. and throughout Canada, operators are now (rightly) more concerned with the required fire and safety standards and how to mitigate risk.

So, what types of safety hazards are found in cannabis growing and processing operations and how can they be safely addressed to minimize risk?

Poor Electrical Work

Although there has been an increase in the quality of installations followed by legal grow operators, instances of improper electrical wiring still occur. Some hazards include:

  1. Bypassing the electric meter by splicing into the service entrance conductors.
  2. Connecting feeder and branch circuits directly to the main service lugs in the electrical panel.
  3. Improper, unprotected splices.
  4. Changing out circuit breakers or fuses with higher rated ones to prevent “nuisance” tripping.
  5. Using non-UL approved electrical system equipment, such as hard-wired extension cords

An easy way to limit these hazards is to ensure your electrical installation follows the provisions of the National Electrical Code (NEC), and that it is permitted, inspected and approved by the authority having jurisdiction (AHJ).

Poor/Loose Connections

Examples of electrical connections include wire splices, terminal connections, switch contacts and power cord/electrical outlet plug-in connections. If a connection is loose, the added electrical resistance can result in localized heating. Eventually the heating can become intense enough to melt conductors and insulation, leading to arcing and the ignition of surrounding combustibles.

Hazards related to poor/loose connections in cannabis grow operations occur most often due to either poor workmanship or housekeeping issues, such as:

  1. Improper electrical connections, such as twisted and taped splices, instead of using approved splice connectors, like terminal blocks or wire-nuts.
  2. Connecting dissimilar metals, such as aluminum and copper.
  3. Contamination such as water, liquids, dirt, grease, at plug-in connections between water circulation pumps and extension cords in hydroponic grow applications.
  4. Poor/loose extension cord or receptacle plugs, which can lose their internal spring tension (aka grip force) over time, leading to a loose connection when a high wattage device is plugged in.

Proper installation methods, good housekeeping practices, the use of UL-approved, quality equipment, and proper maintenance procedures can all decrease the possibility of a poor/loose connection and eventual fire.

Light Fixture Issues

Traditionally, cannabis grow operations have used high-power, high intensity discharge (HID) lighting. Hazards related to HID lighting include:

  1. Combustibles touching the hot lamp glass, which can easily reach over 1000°F.
  2. Mechanical damage that breaks the glass and allows hot particles to fall down and ignite plants, plastic pots or potting material.
  3. Failure due to oil or grease contamination (i.e. touching the lamp with your bare hands).

Competing full-spectrum fluorescent and LED lighting are also available, but they have their own risks, such as installation or manufacturing defects, improper electrical connections to building wiring, incorrect building voltage supply, or cheap, failure-prone power supplies. Another common hazard specific to fluorescent lights is the misalignment of the fluorescent lamps during installation which can cause a poor connection and result in a cannabis fire.

Hash Oil Extractions

THC-containing hash oil is extracted from cannabis and then consumed in small amounts by smoking, vaping or eating. Hash oil is typically extracted from the cannabis plant using butane as a solvent. The most hazardous part of the process is the evaporation of the butane from the solvent/oil mixture, as the evaporated butane fumes are extremely flammable and explosive.

Much like propane, butane is heavier than air, so it sinks and collects at the floor. Performing a solvent extraction in an improper way or in an unsuitable environment is an extreme hazard. Common household appliances and devices can unknowingly ignite a fire or explosion, such as an open flame from a stove, water heater or furnace, or the unprotected sparks from a light switch, refrigerator compressor or laundry machine.

An awareness of these potential hazards can help ensure that persons and property are properly protected through safe designs, installations and practices. This information can also provide clues as to what potential fire/explosion causes could exist in relation to a fire origin and cause investigation.