This month’s column is in memory of Bob Boyer, who passed away in January. For years, Boyer was the director of industry affairs for Edwards, and served on a number of National Fire Protection Association (NFPA) Technical Committees including NFPA 70 and 72.

He also was a past chairman of the board for the Automatic Fire Alarm Association and of the National Electrical Manufacturers Association 3SB Committee.

Onto this month’s topic, which is carbon dioxide (CO2) detection as it relates to the growing of cannabis. As of last November, 33 states had passed legislation legalizing cannabis in some capacity (primarily medicinal use), including 10 that have legalized the growing and selling of recreational-use cannabis.

To increase the growth rate of these plants, CO2 is injected into the cultivation or grow rooms of facilities that are licensed to produce this product.

Be Familiar With Exposure Risks, State Requirements

Here’s your brief science refresher: CO2 comprises about 0.04% of our planet’s atmosphere and is the primary carbon source of Earth’s life. Atmospheric CO2 is used by plants for photosynthesis, which in part produces the oxygen that is required for life.

CO2 is also used as a fire suppression agent, a refrigerant and a means of carbonating beverages among other uses. In last February’s column I discussed CO2 detection solutions for installation in locations that implement CO2 for the dispensing of beverages.

For the production of cannabis, around 2,000 parts per million (ppm) of CO2 is locally placed into the atmosphere of the grow rooms. This is not a fatal concentration for human life; a lethal dose is 90,000 ppm for five minutes.

The National Institute for Occupational Safety and Health (NIOSH) has set a permissible exposure limit at 5,000 ppm and immediately dangerous exposure to life or health at 40,000 ppm.

Depending on which state you work in will determine if the production of cannabis is legal. Each jurisdiction within the state may then have its own local requirements for both fire detection and CO2 detection. I’ve now seen several jurisdictions require CO2 detection within a space in which CO2 is being injected.

The state of California, in which I am based, added requirements for CO2 detection to the 2016 California Fire Code, July 2018 Supplement. These requirements are not found in Chapter 9, or Section 907, however, but rather Section 5307, Compressed Gasses not Otherwise Regulated. This may become the model for other jurisdictions.

Codes Detail System Scenarios, Detector Placement

The new language is for CO2 enrichment systems, in which more than 100 pounds of CO2 is being used. There is to be a low-level alarm upon the detection of 5,000 ppm and a high-level alarm upon the detection of 30,000 ppm.

The code then requires the following to occur when these levels are reached:

• Low-Level

1. Stop the flow of CO2 to the piping system
2. Activate the mechanical exhaust ventilation system
3. Activate an audible and visible supervisory alarm signal at an approved location within the building

• High-Level

1. Stop the flow of CO2 to the piping system
2. Activate the mechanical exhaust ventilation system
3. Activate an audible and visible evacuation alarm both in-side and outside of the CO2 enrichment area, and the area in which the CO2 containers are located

The CO2 detectors are to be located within the enrichment area within 12 inches of the floor. This is due to CO2 being heavier than air, so it will sink first to the floor and then travel upward as it fills the space.

Most of the area fire departments in which these facilities are being constructed are requiring that these CO2 detection systems be integrated into the building’s fire alarm system. In some cases, the installer of the CO2 piping system also is installing the detectors, but in most cases this is not within their scope of work and falls back on the fire alarm contractor.

The notification within the premises cannot be via the appliances that are used for the building’s fire alarm. NPFA 72 requires that the fire alarm signal be distinct. NFPA 72 notes that if the notification appliances are used for other warnings that the words “Fire Alarm” or “Fire” cannot be on the appliance.

The audible sound cannot be the temporal-three, but must be different such as a high-low, solid or other such tone. Temporal-four also cannot be used, as this is reserved for carbon monoxide (CO) detection systems.

As the cannabis industry expands and you are requested to provide a bid for the life-safety system, remember to check with the local authority on what requirements they may have regarding CO2 detection.

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