Photo by Paul Wellman

With about 500,000 square feet of greenhouse production, 22,000 square feet of manufacturing space and about 10,000 square feet of processing in Santa Barbara County, Calif., the Glass House Group follows multiple-step processes to ensure product safety at its cultivation facility, Glass House Farms.

To provide top quality products and pass product testing, the Glass House Group uses air purification to help prevent undesirable bacteria, fungi and spores from taking hold, says founder and President Graham Farrar.

“Making sure that you have the ideal climate first is a fundamental piece of growing well, and filtration and clean, good air with the right chemistry is a key part of that,” he says.

Farrar offers these four tips for better air purification in cultivation, manufacturing and processing.

1. Identify what needs to be removed from the air and try to resolve the issue before filtering.

In cultivation, Glass House Farms tests for spores of salmonella, E. coli and Aspergillus—a mold that California regulators also test for—and uses purification to help eliminate any that may be present in the air. Some filters also can remove spores that cause plant diseases like powdery mildew and botrytis.

Cultivators who are trying to filter out fungal spores like Aspergillus must first determine the source, Farrar says. “I think the best filtration starts with reducing, mitigating, eliminating whatever it is you're trying to filter first, and then using your filtration to remove anything that still remains.”

2. Make sure your fan is pushing the correct airflow through your filter.

Air filters should include a chart with the cubic feet per minute (CFM) of airflow they are rated for, Farrar says. Some growers push too much airflow through their filters and don’t leave enough “dwell time” for the system to filter the air, he adds.

“If someone's throwing you a ball and they throw it at you as fast as they can, it's really hard to catch it,” Farrar says. “The filter has the same issue, which is, if you jam the air past it at 50 CFM when it's rated for 25, it doesn't work very well because everything's going by so fast that it can't pull it out.”

3. Dehumidify air before sending it through the filter.

Humid air can clog a filter, Farrar says. One of the ways cultivators can avoid this is by dehumidifying their air before it reaches the filter.

“The No. 1 way, in a greenhouse, to decrease humidity is to not add any humidity that you don't need,” he says. “For example, if you irrigate plants, they almost always have what they call ‘overdrain,’ which is water that comes out the bottom [of the plant container]. Keeping that water—which if left on the floor would then evaporate and add humidity—out of the greenhouse is one of the biggest things you can do to keep the humidity down.”

Growers also can install dehumidifiers, Farrar says.

4. Clean the filter regularly, especially in humid environments.

If relative humidity is high, cultivators should clean or replace their air filter more regularly to prevent the filter from clogging, Farrar says.

“If you're filtering the air that’s at 80%, for example, maybe from a plant dry room, that carbon filter is going to go down in efficiency a lot quicker than if you were putting 40% humidity air through it,” he says.

Patrick Williams is a senior editor for Cannabis Business Times and Cannabis Dispensary.