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Getting thru the Smoke on Marijuana Processing Plant Gas Detection

Posted by David Petersen on 5/1/2019 to Tech Tips
A new life safety concern is growing (literally) in the US. It is the growing and processing of Marijuana in facilities across the country. The required knowledge to outfit one of these facilities is huge, besides being a Fire Alarm expert, Sprinkler, Hazardous Material Handling, Explosive Gasses Expertise, Suppression, HVAC and Mechanical Expertise also required. 

The Marijuana Industry is an expanding one utilizing today’s science to produce useable Marijuana products for both recreational and medicinal purposes. The use of chemicals and gasses to extract the useable components of the Marijuana plant has evolved in a short amount of time and has created new worries for health and fire safety professionals. 

Let’s talk about these materials needed in the growth and extraction of Cannabis Products as well as some of the consideration for Fire Alarm Professionals to be aware of. AHJs across the country must also have an in-depth knowledge of the chemicals and gasses that may be present in these facilities and how to detect and how to respond to these facilities. 

Carbon Dioxide (CO2) is an “asphyxiant” gas and is not only used to enrich the growing rooms atmosphere, but us also used in a liquid form it extract the oils from the plants. As a gas it robs the air of Oxygen and while that is good for plants, it is no so good for people. Most growing facilities will enrich the grow rooms with CO2 as the plants use this for Photosynthesis (their method of turning sunlight into energy to grow). The more and the larger the plants, the more CO2 is needed. Typically, if there is less than 100 lbs. of CO2 stored on site there is no need for special detection, however, if there is more and/or there is CO2 generators on site, some detection is required depending on the concentration in the room. CO2 detection, when required, must not just detect the presence of harmful levels of the gas, but must also shut off the gas supply if the facility is not constantly attended. CO2 concentrations are referenced below: 

Normal 300-600 ppm Infused 
Growth Levels 1,000 – 3,000 ppm 
Alarm Activation Level 5,000 ppm 
OSHA Level 30,000 ppm 
Lethal Level 100,000 ppm 

Liquefied Petroleum Gasses (LPG) such as Propane and Butane. These gasses are explosive and heavier than air so they cannot be used in basements, pits and other areas where the gas can collect (check NFPA 58 for container locations). No Smoking signs are required and Fire Extinguishers are also required based on NFPA 58 (not NFPA 10). At any time, when these gasses are being used a Fire Sprinkler System must be installed. You will find that sprinklers must be installed for a number of reasons in these facilities including Plastic or Polyethylene wall coverings, 12,000 Sq. Ft size of the building and limited access and egress to growth and processing areas. The detection of LPG is based on the Explosive level of the particular gas, you will see references to a % of the LEL or Lower Explosive Level. Different gasses will require detection of leaks at levels much lower than this LEL (25% lower per NFPA 1) for example: 

Propane 
LEL 2.1% vol. 
Alarm Activation Level 1.58% vol. 
Butane 
LEL 1.9% vol. 
Alarm Activation Level 1.43% vol. 

There are Water based and Solvent based methods as well, but gas detection is not an issue with these types of processes. 

Ventilation of these gasses after they have done their job and the valuable oils have been extracted depends on the gas. CO2 gas is generally vented to the exterior of the building whereas LPG gasses are exhausted thru a ventilation system that is explicitly manufactured for use in explosive atmospheres, this includes evaporated solvents and the remaining solid matter (see NFPA 91). These gasses are either reused in a closed loop system or safely vented into the atmosphere. 

There are Water based and Solvent based methods as well, but gas detection is not an issue with these types of processes. 

Detection for these gasses is based upon the type of gas present. As specified previously CO2 Detectors must be set for 5,000 ppm and LPG Gas Detectors for 25% below the gasses LEL (LFL if it resides in a liquid state). Examples of some of these detectors are available in the links below: 

For Carbon Dioxide (CO2): 

For LPG Gases (Propane, Butane, etc.) 
(***If the requirements are for Class 1 Div 1 or Div 2, then explosion proof devices, Listed for the purpose are required***)

If CO2 is generated on site, a Nitrogen Dioxide (NO2) Detector is required as propane is used as a supply gas: 

There are a lot of processes and Codes to follow for these types of installations, both electrical and mechanical besides those mentioned above: 

NFPA Standards: 

NFPA 1 – Fire Code (Chapter 38 Marijuana Growing, Processing, or Extraction 2018 edition) 
NFPA 13 – Standard for the Installation of Sprinkler Systems 
NFPA 30 – Flammable and Combustible Liquids Code 
NFPA 55 – Compressed Gasses and Cryogenic Fluids Code 
NFPA 58 – Liquefied Petroleum Gas Code 
NFPA 70 – National Electrical Code 
NFPA 91 – Standard for Exhaust Systems for Air Conveying of Vapors, Gasses, Mists and Particulate Solids 
NFPA 497 – Recommended Practice for the Classification of Flammable Liquids, Gasses, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas 

International “I” Codes 

International Building Code 
International Mechanical Code 
International Existing Building Code 
International Fuel Gas Code 
International Plumbing Code 

As always you can contact us here at TC LifeSafety, Inc. at 800-837-8175 or write us at [email protected]

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