Photocatalytic Oxidation for Cannabis Grows: Fatal and Potentially Dangerous Flaws

Powdery mildew is one of the most common and destructive contaminants of cannabis, and industry regulation is taking note. Tackling the growing conditions – especially non-hygienic environments – takes a layered and multi-faceted approach.

Air Filtration Vs. Purification
Air filters capture and hold particles. The basic premise is quite simple… a particle of a certain size approaches the filter media, it is either captured by being pushed against a hole smaller than itself, electrostatically attracted to the filter fibers and sticks to it like a magnet or a combination of both.

Photocatalytic Oxidation (PCO) inactivates potential harmful gases or biological contaminants. Arguments against air filtration claim air filters become ineffective as they become clogged (i.e. capture contaminants) and need to be replaced on a regular basis, whereas some PCO technologies require little maintenance or impact to their performance over time.

PCO devices have a large quantity of small clear quartz rings doped with Titanium Dioxide. When combined with a fan and a UV lamp, this creates catalytic chemical reactions. These chemical reactions use wavelength energy from the UV lamps to either break down airborne chemicals or convert them into other chemicals on the clear quartz rings. This process ONLY works for as long as the quartz rings remain clean (a challenge in dirty, sticky cannabis environments). Eventually quartz rings are coated by both dirt and trichomes, rendering them useless and in need of replacement, an endeavor much more expensive than replacing a filter.

The American Society of Heating, Refrigeration and Air Conditioning (ASHRAE) has a 125 year history of providing valuable research and design standards underpinning every single heating, air conditioning and air moving device across the world.  They summarize their findings regarding filtration vs. purification technologies as follows (1):

  • “Mechanical filters have been shown to reduce significantly indoor concentrations of airborne particles. Modest empirical evidence shows that their use will have positive effects on health.”
  • “Photocatalytic oxidation technologies have been shown to remove harmful contaminants, to be ineffective in removing contaminants, and/or to generate harmful contaminants during the air-cleaning process. There are no data on how their use affects health.”

ASHRAE maintains the position that mechanical filters are the most effective technology available to substantially reduce airborne contamination. PCO technologies have been shown to reduce harmful contaminants, but have also been shown to produce harmful contaminants during the air-cleaning process.

NASA has also done studies with PCO technology and its research (done on potatoes) is often leveraged to back PCO based products on the market. Most of these products are for food preservation through the removal of ethylene gas. Ethylene gas is created naturally from growing plants and contributes to the spoilage of food. It is safe to say that the tightly controlled environments on the space shuttle are not representative of the growing facilities here on earth, especially those of a cannabis facility. More importantly, in cannabis grows with powdery mildew spores, the intent is that PCO will destroy spore particles entering the device. But all that goes into the device is then discharged back into the room. If the PCO device is inevitably dirtied and rendered inefficient, it becomes a source for spreading powdery mildew contamination rather than eliminating it.

An Emerging Hazard
When PCO is exposed to the ethylene gas generated by plants, it will usually break down into water and carbon dioxide, generally harmless molecules. However, there is a growing body of evidence (2 3 ) that shows the presence of primary airborne cannabis terpenes (volatile organic compounds – VOC’s) pushed across a closed room photochemical converter (i.e. PCO) can generate secondary VOC’s such as formaldehyde and acrolein due to incomplete decomposition of the VOC compounds. These studies are important because they are showing that VOC’s don’t fully breakdown inside of a PCO and more importantly, are decomposing into potentially toxic chemicals. Continued research is required to determine the impact to personal health this has for those working inside active grows with PCO devices. However, out of an abundance of caution, grow operators should consider the potential liability and health hazards that could result from installing PCO devices in light of this research.

The Fantastic Filter
Filters have been on the market for over 100 years, but it’s only been in the last 10-15 years where real material science has played a key role in optimizing both particulate arrestance and energy efficiency. A filter has lots of pleats, which are similar to a piece of paper being folded many times in an alternating z-pattern. The entire filter will sit inside a cardboard cellulose frame or a plastic/metal housing. Whatever the mechanism or construction, a filter is designed to capture and hold contaminants indefinitely without the possibility of the contaminant leaking past or through the filter.

Filters are officially tested and rated for efficiency as Minimum Efficiency Rating Value (MERV) and the scale ranges from MERV 1, at the very low end, up to MERV 16, which holds similar standards to High Efficiency Particulate Arrestance (HEPA) filters. Depending on the actual application, an air filtration system can be designed to capture the contaminant in the environment using the proper blend of filter materials and filters.

It’s a common mistake to think that more filters are better, despite some air filtration on the market units having up to six filters. Proper filter selection should be determined by the contaminants needing removed, energy usage, cost of filters, and filter replacement cycles. At Element Grow, we leverage our experience in heavy industrial facilities, paired with real world testing and customer feedback to provide a range of filter options depending on the environment it will be used in.  Food processing, extraction labs, mold remediation or smoke mitigation may require different filter options to properly address their specific needs and we’ve worked hard to have a real solution for each application. For GMP-certified facilities, the primary focus is on 100% capture of biologically viable particles, such as powdery mildew spores. We’ve selected a combination of filters that balance energy costs with filter costs, while maintaining near 100% spore arrestance.

A Regulatory Horizon
Canada, the European Union and other international governing bodies have an established framework for safe production of products destined for human consumption. The United States’ FDA has the same standards, however it is currently not applied to hemp and cannabis product production. Since hemp was legalized, the FDA has been playing catch up and it would be wise to anticipate the enforcement of regulations in the near future. This regulatory framework is called Good Manufacturing Practices (GMP).

GMP is a set of operating standards that focus on both providing production in a safe and certifiable clean facility paired with extensive quality control procedures and documentation. A deeper dive into GMP regulations shows a focus around the creation of clean facilities and contamination control along with evidence that airborne particles play one of the key roles in spreading contamination into consumable products. Each international regulatory agency has its metric, however, the general consensus is any airborne particle larger than 0.5 microns has the potential to carry a viable biological contaminant. A certain number of particles of specific size ranges are allowed depending on the process in your facility (processing, packaging, etc.). However, the important takeaway is that air filters for particle capture are the only solution officially recognized to provide facility GMP compliance. Additionally, all equipment in a GMP facility must be chemically sanitized on a regular cycle to ensure the integrity of sterile environments exposed to the consumable products.  In short, if the intent of your operation is to be GMP compliant, you need to create a cleanroom environment that meets those regulatory standards and that can only be achieved with air filtration.

Photocatalytic Oxidation devices, UV technology or otherwise, are not part of any recognized GMP compliance framework for a simple reason: There is no particle capture and they can’t be chemically sanitized. As we noted in prior sections, the efficacy of a dirty PCO unit drops dramatically, however a dirty filter will always carry the same capture efficiency.

At Element Grow, we have an eye on the future of regulations and have developed the Element Grow E2 Air Filtration Unit with E-Guardian Monitoring to directly address demands of GMP compliance. The units’ ability to create an ISO cleanroom in less than 30 minutes of operation paired with active onboard air monitoring and GMP-reporting features sets a standard of what smart facility contamination control should look like.

The Bottom Line
We fully recognize that we’ve been downplaying the significance of PCO and UV systems. These technologies do provide benefits in certain situations. Our intent is to simply show that you need the right tool for the job. If GMP compliance is your focus (or you are looking toward preparation for its requirement in the future), you need to take a serious look at air filtration technology that fits your facilities needs. UV lamp sterilization systems have shown to be very effective at controlling biological growth within HVAC equipment (i.e. on the cooling coils), and to a lesser extent, have shown to help breakdown airborne chemicals into lesser harmful compounds. When we apply air filtration or purification technology into cannabis grow facilities, there is no silver bullet that solves all problems with one device. True powdery mildew free facilities require a layered defense that starts with a clean, particle-free facility and is paired with best growing practices and cleanroom contamination control procedures. If you’re trying to preserve fruits and vegetables, PCO is proven to help. Cannabis and hemp growing and processing facilities should stick to tried and true particle capture technologies.


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