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Mold Control...Air Filtration/Photocatalytic Oxidation

The answer to your question is yes. Sorry it took so long for me to get back with you.



Environmental PM prevention.

with out consideration of filtration of atmosphere and possible recontamination of environment with new inoculum, keeping leaf surface temp between 80 and 90 degrees and once a day let it creep up to 95 and keep it there for 30 min - 1 hour and as long as you do not permit let leaf moisture build up for over 10 hours per day almost any preventative course will work. Because whats there wont propagate and re-inoculate plant surfaces until you can get the brix up to 12+

what this means is raising the leaf surface temp high enough each day as to kill off the conidiospores (which need 1/3 to 2/3 the leaf surface moisture interval to re-inoculate)and keep the leaf surfaces dry enough that the ascospores cant emerge and re-inoculate the plant surfaces. this means utilizing direct ventilation on those same surfaces so the moisture wont build up over time. Now all you have to deal with is the hyphae. that is where you must do something direct perhaps as simple as spraying with a bit of alkaline water or a light sulphinated botanical suffactant or citric preparation. These a mainly leaf washes that do destroy spore but also clean away the dead hyphae. However once hyphae infest the buds themselves it is difficult to control the leaf surface moisture intervals of the inner bud much less destroy the inoculum and clear away the failing hyphae.

So pretty much that bud to the level of its infestation is pretty much going to be a PM factory until it is consumed by fire or rendered inert through submersion. but any physical treatment preventative or curative will work much better if at all once the min max leaf surface temperature and leaf surface moisture levels are kept with in check



Fascinating post. Sounds like some serious commercial greenhouse agricultural experience.

I am curious about how one would implement this strategy with cannabis. What comes to mind is you could raise the leaf surface temp to 95 by controlling the hvac system such that the lights would raise the surface temp. This would seem an easy thing to raise the surface temp of the top leaves, but more often than not PM seems to start in some of the lower leaves that are not sufficiently exposed to the lights. While many growing strategies promote removing a large percentage of the leaves, it is a labor intensive process and in some cases, i.e. “sea of green” virtually impossible.

You mention that PM will not propagate and re-inoculate plant surfaces until the brix is 12+. My understanding is that 12+ represents a very healthy plant. Does that mean that unhealthy plants will not develop PM?


This is good but remember HID lighting has lots of IR which causes heat and often your leaf surface temp will be 5 - 7 degrees F higher that your air temp. Plus leaf moisture intervals must be accounted for. this is why having adequate ventilation is a must and the buds leaning up against the wall or in dead air space like the corner get PM first sort of like the unders that don’t get good air flow.

another point is keeping leaf surface moisture from existing for more than 4-6 hours a day is a big part of the equation. Remember with HIDs you need good a/c unit because of the heat they put off. However when the lights go off that heat goes away and the temp falls and the humidity rises and so does your leaf surface moisture levels. LEDs put off way less heat so the night time temp conversion is lessened as is the need for mega oversized de-humidification equipment. the A/C can keep up with the temps easily and the transition inst nearly as large and simple de-humidification systems work adequately. plus you save a cubic shit load of power from both the A/C and the lights.

I must have gotten that backwards PM will not reinoculate a plant with brix higher than 10-12. but that wont stop it if the plant has be inoculated with the PM already. only preventative temp levels both day and night low leaf surface moisture intervals once you achieved this you can spray your mild sulfanated oils botanical oils and safe fungus control products like procidic or simple sulfer dust can do big work on your existing CFUs (colony forming units), condiospores and cleistothecia.

so keep up the spraying in veg and pay close attention to the environment during the las 4-6 weeks of flower and you will go along way to defeating the PM monster

here are some interesting links on the sugject:


At SDI our equipment tracks and controls conditions through the photo and non photo periods, minimizing localized out of control conditions that occur during transitions


Ron, what do they say about volitolized sulfur. It’s S8 with a molecular weight of 32.

Hop growers would go out of business without sulfur of s8. Doesn’t Washington state have the greatest number of hops production.

If the sulfur burns in your heating unit, you have other problems. You get sulfur dioxide. Or worse sulfur monoxide. Both of these are highly reactive with water. One gives you sulfuric acid.

If you sublimed the sulfur in the heater correctly, you maintain the sulfur in an elemental form of S8.

There is also a mono hydrate form of sulfur, but it should not be confused with S8. I would sometimes see in places with lead mines and fools gold.

insecticidal soap, which is a potassium salt of fatty acids has S8 in it to keep the insecticidal soap from separating, when added to water. If your water is very hard and a ph aubove of 7.5 you have to either add pure acid or more sulfur. To keep the insecticidal soap separating.

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This is an outstanding piece of work.

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I’ve got these in one zone in my greenhouse, we hung 6 of them in 3000sqft. I’ve only had one harvest out of this zone so far. PM pressure seemed lower but then it rained for a month and it crept back in. I’m not sure yet if its worth the investment, I would say it depends on the facility design.


“I’ve got these in one zone in my greenhouse, we hung 6 of them in 3000sqft. I’ve only had one harvest out of this zone so far. PM pressure seemed lower but then it rained for a month and it crept back in. I’m not sure yet if its worth the investment, I would say it depends on the facility design.”

You are very correct facility design and location would be critical.

Went it’s dark, wet and humid outside trying to control humidity takes work. I always hope it’s cold enough outside to drop my humidity inside. I would pay money for the days that’s not true. All my big problems as a professional grower came when the weather was at its hardest. Cool, wet, dark and 65 outside. What do you do?


These products from Proguard are producing Ozone Not what you want.


There are some sulfur products on the list of acceptable items but they still don’t have any registered products for burning that I know of. I personally have no need for it but know of a grower that got in a lot of trouble when the WSDA visited their grow and found a burner and sulfur being used.



You don’t want to burn the sulfur!

You heat the sulfur up to 240 degrees. The sulfur melts and sublimes into the air in the exact same molecules form.

Works great.



I don’t use any type of sulfur or other pesticide for that matter. My original comment was to warn other Washington growers that “burning”(the most common term for vaporizing) sulfur is not allowed in the I-502 system at this time. I hear of growers recommending all the time and some people don’t know they need to check with the state regulations before just using things that people recommend especially when each state has specific regulations about what is and what is not acceptable.


There’s a lot of confusion surrounding what treatments are available and acceptable in which jurisdictions. For that very reason, Growers Network is preparing to launch the world’s first fully indexed Pest and Disease Database, which will allow you to easily answer these questions for yourself without having to dig through state issues regulatory guides. Stay tuned for more!


Agreed every state seems to have its own regulations.

Wonder how they would handle calcium sulfate? We added to our fields every years. For both the calcium and the sulfur.

When we final retire to Washington State. I suspect we will learn a lot of new techniques for our display gardens.

@ron sorry for any confusion.


Several months ago I started this thread in an effort to learn more about photocatalytic-oxidation as a potential tool in managing mold, mildew and odor issues in a grow room. Thought I would update what I have found so far.

I have over 20 years of experience growing cannabis and during that time I have experimented with nearly every “new” technology introduced to the market. What I have found is that cannabis, being a very profitable cash crop, it creates a willing market of buyers willing to overpay for an over hyped product. The single most egregius source of these products seem to be those involving nutrients and electronics. In the case of the Photocatalytic Oxidation (PCO) systems the unit price on the system I originally inquired on was around $3K. While a lot of $, one could justify it if the applicable grow increases production by just 2%. And, if it does that without the use of pesticides/fungicides that may run afoul of all the new product testing laws it is a win/win.

What I have found so far is inconclusive. A couple of folks have posted that they have installed some PCO systems and they “like” them, but they did not offer any objective production observations about them. The various manufactures all speak of NASA developed technology. Perhaps a few on here may recall the promise of NASA developed lighting, i.e. Plasma. How’s that going? Some offer ozone generators renamed, with fancy names such as “Multi Cluster Ionization Technology”. Best as I can tell, that is a fancy name for an Ozone generator. Anyone looked at the health risks of ozone? I bet your state occupational health folks will if they know you are using ozone.

I have found that PCO technology works good for odor reduction. I sort of backed into this one. I purchase a $350 in duct unit ( ) from a company called RGF (bought it on ebay) that I had planned to try in a 800 sq. ft bloom room. Before getting around to installing it a number of visitors to our place pointed out that there was easily detectable odor outside and we should do something about it. With the PCO unit just sitting on my desk and the thought of installing a carbon filter system with an endless stream of new filters the size of a hot water heater plus the added noise of a fan I thought why not try out the PCO unit in the building hvac system. Virtually nothing to lose, I already had the unit and cutting a hole in the duct took all of 15 minutes. Within an hour the odor problem was solved. The unit did not completely eliminate odor indoors, but it reduced it to the point that it was not detectable outdoors. And, except for the days that we trim, the odor indoors can be masked with simple air freshener.

Hopefully in the next few months we will pick up another unit and try it in the bloom room. At the moment I have been engrossed in the concept of tissue culture as a way to improve the quality of our propagation stock.


The unit you installed from RGF produces Ozone. Our product does all the same without producing Ozone. Our product also keeps your HVAC coils and duct work clean and free of everything you fight daily.