Inspection Guide for Marijuana Extraction Facilities
Inspection Guide for Marijuana Extraction Facilities

Inspection Guide for Marijuana Extraction Facilities

Before moving to FABULOUS Las Vegas, I hadn’t heard of marijuana extraction. Marijuana extraction is a method of combining flammable liquids with marijuana and extracting potent compounds from the plant, usually in the form of cannabis oil. It is a process that is complicated, and installations should be left to qualified electrical contractors since it involves classified (explosionproof) areas, specialized wiring, and expensive equipment. It is my opinion that an electrical wiring installation should not be attempted unless the electrical professionals are 100% willing to commit to familiarizing themselves with the entire process and the equipment involved. As the wiring electrician, study the blueprints and make sure that no portion of the electrical design is “left to others” or “to be determined (TBD).”  A room where marijuana extraction takes place has the potential for explosions due to the nature of this process.  In this article, we will deal with National Electrical Code (NEC) and other basic electrical requirements for marijuana extraction facilities and how the inspector can avoid some of the common pitfalls.

For the purposes of this article, I will be using the 2017 National Electrical Code (NEC). There is very little information in the NEC for this subject other than Article 500 entitled Hazardous (Classified) Locations, Classes I,II, and III, Divisions I and 2 and Article 501, Class I Locations, and possibly Articles 504 and 505.

I say very little information because a large part of any extraction installation depends on the specific equipment, where it is being located, and how it is being used. Also, current 2020 NEC provides no mandate for backup power in plant oil extraction facilities. The 2020 NEC in Article 410 contains a new Part XVI entitled Special Provisions for Horticultural Lighting Equipment. However, this new article specifically applies to where plants are grown and not where plants are processed. It is of little or no use to us when discussing plant oil extraction facilities.

For starters, we need to determine how the NEC interrelates with other codes and go from there. Chapter 38 of NFPA-1, Fire Code, Chapter 39 of the International Fire Code can be a good starting point with which to gather information.  We can learn from these standards that there needs to be a room that is solely dedicated to the extraction process.  This is the room where hydrocarbon solvents are used in a listed extraction machine in order to produce the oil. There can be no other equipment in this room, other than the extractor(s) and equipment only necessary for the extraction process.  If one takes the time to research the extraction equipment, they should check and make sure that it is listed for Class I, Division 1. The room should include a gas detector.

The gas detector must be wired according to NEC 500 and 501, and the location of the gas detector is usually left up to the discretion of the authority having jurisdiction (AHJ), which could include the fire inspector or fire plan-check personnel.  There can be no additional equipment inside the extraction room, unless the equipment is also listed as Class I, Division 1.

The two most common extraction methods that I encounter are (1) butane, and (2) ethanol.

Taking a quick look at Article 500.6(A)(3) and 500.6(A)(4) for material groups, we can read that an example of Group C is ethylene (think “ethanol”), while an example of Group D is propane (think “butane”). All wiring must be in rigid conduit or threaded steel intermediate metal conduit and will need to have seal fittings installed per 501.15(A).  Equipment schedules are important, and one should ask for an equipment schedule during the plan review process, to make sure of what is taking place inside the extraction room and also the surrounding areas.  Ask for a complete schedule for the extraction equipment (classified location) and the post-extraction equipment (unclassified location). We will talk about post-extraction a bit later.

Chapter 38 of NFPA 1 specifies that there should be some type of emergency backup for the mechanical system, extraction room lighting, and gas detection system, in the event of power failure. Did anyone manage to watch the YouTube videos of the recent cannabis-factory explosion in Los Angeles?

Although the 2017 NEC does not mandate emergency backup (and neither does the 2020), a good, safe design will include some system of emergency backup to keep the exhaust running in the event of power failure. The author of this article wants to submit a Public Input to the 2023 National Electrical Code to suggest a separate chapter for plant oil extraction, time permitting. I believe that the level of danger involved warrants that these facilities have their own dedicated section of the NEC.  All electrical equipment in the extraction room or booth and within 3 ft (900 mm) of any opening (doorway) is in a classified location. One can minimize the use of classified wiring methods if the installation is carefully planned out by the design professional. Outlets, control panels, and panelboards can usually be kept outside of the extraction room and completely outside of the 3 ft (900 mm) zone, away from any openings. It should be noted that Section of NFPA-1 requires that all electrical components within the extraction room be interlocked with the hazardous exhaust system such that room lighting and other extraction room electrical equipment will only operate when the exhaust system is in operation. Some have commented that “it’s like a paint spray booth.” This is true in one respect, in that potentially explosive vapors are exhausted.

But extraction rooms are quite unique unto themselves. The extraction machine that is used with the butane method, for example, recaptures all of the butane in what is known as a closed loop-system. The butane is used to “extract” the oil, and then the butane is 99.9% recovered back into the extraction machine. So, the process never reaches a point where the hazardous material isn’t always present. And please do not let the term “closed-loop” fool you. It isn’t really a closed system, electrically speaking.  At some point, the machine will need to be opened, and the product (the cannabis oil) will need to be removed.  It is at this moment in time that the flammable vapors are present and can possibly be at or above the lower flammability limit (LFL), even with the constant exhaust. Denver Fire Department personnel pioneered the effort to classify extraction rooms, and they did the original research for these type of facilities.  They measured extensively the amount of vapors present during the entire extraction process.  Below is an excerpt from the Denver guidelines:

“This Class I Division I requirement was based on flammable gas metering of several extraction processes, all of which exceeded minimum LFLs during equipment opening for oil retrieval and removal of LPG-laden plant material in addition to other known equipment and accidental process failures releasing LPG.  Flammable gasses are present during normal extraction operations, therefore this location meets the definition of a Class I Division I location per the NEC…”

Receptacles, switches, lighting, and utilization equipment inside the extraction room all need to be rated Class I, Division 1.  I can sometimes allow luminaires rated Class 1 Division 2 for certain ethanol extraction room designs provided the room contains a backup power source. This might be permissible and acceptable to the AHJ if the plan review is accompanied by documentation from a mechanical and chemical engineer based on sound engineering practices [see 500.8(3)].  That being said, I would never allow luminaires under a hood for any type of flammable gas to be rated other than Class I, Division 1, even with a backup power source.  And when the flammable gas is butane, literally everything (all equipment) in the room should be rated Class I, Division 1, in my opinion.

As an electrician, it is important to remember that any motor located in an airstream that may contain flammable vapors during normal processes must be rated for Class I, Division 1; you will need a proper explosion-proof electric motor per Section 501.125. But again, many times motors can be located such that they aren’t in a classified location.

After the cannabis extraction technician has completed the extraction process and captured the golden cannabis oil, the process is ready to move to post-production. Post-production involves taking the oil and processing it or refining it even further. It involves flammable vapors, but usually involves lower quantities of flammable liquids and thus can be accomplished outside of the extraction room. The way I usually see a post-production set up is that the lab contains vacuum ovens or roto-vap machines (or both) to draw any remaining LPG out of the oil, making the product as pure as possible. These machines need some type of exhaust, and the exhaust system must be left up to the mechanical design professional. In a worst-case scenario, a chemical fume hood can be used per 2018 IFC 3903.5, although NFPA 1 seems to allow for an “approved” exhaust system installed in accordance with NFPA 91,  Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids or the mechanical code. To reiterate, Chapter 38 of NFPA 1 also provides requirements that there should be some type of emergency backup for the mechanical system, in the event of power failure.

If you remember one thing from this article, remember this — equipment matters.  It’s part of the overall design. It is important to remember that any equipment being used in the extraction process, as well as the post-extraction process, be listed for use – for that particular purpose.  For example, the winterization of oil can become dangerous when stored in large quantities.  It must be kept cold, so there is no chance for flash (explosion). A specialized freezer must be used, and it should be listed and labeled for use with flammable liquids, and in addition, be able to reach at least minus -80 degrees C for butane winterization. The flashpoint for butane is -60 degrees C.  So, by going down to -80 degrees, and making it that cold, it’s not liberating any flammable vapors.

This is just one example this article intends to emphasize – that there need to be zero unknowns when it comes to the specific equipment. This is the only way to ensure safe wiring. To reiterate, in order to correctly accomplish a safe electrical installation, it is my opinion that the electrical plan reviewer, the electrical inspector, and the electrical contractor become familiar with the cannabis extraction process, the many steps involved, and the specific equipment. It can be a daunting task. A job like this is more than running wiring from point A to point B.

Last but not least, grounding and bonding needs to be taken into consideration. The NEC does not provide any real guidance on bonding for marijuana extraction facilities other than Article 250,  Grounding and Bonding, and neither does the IBC or NFPA-1.

NFPA-1 Chapter 38 attempts to do this, but in my opinion, what is contained therein isn’t close to being sufficient.  In my opinion, extraction equipment in the extraction room, including all un-energized metal parts, will need to be bonded together and to the grounding means.  Some examples of what should be bonded together could include the ceiling grid, stainless steel tables, metal equipment, extractors, steel wall panel coverings, metal hoods, Class I Division 1 scales, etc. It is not enough to simply rely on electrical connections in order to provide the bonding, as equipment can become unplugged for a period of time.  In addition, various manufacturer’s installation guidelines call for certain machines to be bonded separately. In my opinion, I would suggest an equipment ground terminal bar and a 6 AWG solid copper conductor to accomplish this task because a 6 AWG is the smallest size that can be installed unprotected per NEC 250.64(B). My choice for a 6 AWG solid copper conductor is strictly for reliability.

I would like to thank Todd Laberge, P.E., Fire Marshal for Lawrence Berkeley National Laboratory, for helping me understand the marijuana extraction process and the many hazards involved. To reiterate, I hope to submit a Public Input to the 2023 NEC to have marijuana extraction added to the document, in a dedicated chapter. There are too many electrical nuances specific to plant oil extraction, and I feel that this process deserves a dedicated NEC chapter.  If I can be of service to anyone with regard to electrical for these types of facilities, please do not hesitate to contact me.

Nick Sasso
Nick Sasso has worked as an electrician's helper, journeyman electrician, master electrician, electrical contractor, electrical inspector, electrical plans examiner, chief electrical inspector and building official. He is an electrical contractor in four states and has served in court cases as an electrical, ADA and building-code expert. In 2005, Nick was appointed by Gov. Jeb Bush to the Florida Building Code Administrator's and Inspectors Board. He was subsequently reappointed by Gov. Charlie Crist. In 2014 Nick was appointed by the National Fire Protection Association (NFPA) to Code Panel 5 (grounding and bonding) – National Electrical Code. In 2019 Nick was appointed by the National Fire Protection Association (NFPA) to Code Panel 9 (switchboards and panelboards) – National Electrical Code In addition, Nick Sasso serves on UL standards committees STP 1081 (Swimming Pool Pumps, Filters and Chlorinators), STP 2452 (Swimming Pool and Spa Cover Operators), STP 22 (Amusement and Gaming Machines), STP 3030 (Unmanned Aerial Vehicles - Drones), and STP 1389 (Standard for Plant Oil Extraction Equipment). He works as an electrical plans examiner and can be reached through his website, The comments and views expressed herein do not necessarily reflect the views of his employer, the NFPA, UL, or any code panel. Follow Nick on Twitter! @ChiefNickNEC.