Sanitizing & Cleaning the Cannabis Grow Room Part III: HVAC & Air Systems

In Part I of our Sanitization Series, we outlined the importance of keeping to a regular inspection and cleaning schedule, and the difference between sanitizing, disinfecting, and sterilizing your grow room.

In Part II, we discussed how to sanitize your plants and substrate, and how cultivators can prevent damage and loss to crops from bacteria, fungi, pests, and plant diseases.  

To conclude our Sanitization series, Part III delves into the importance of sanitizing your grow room HVAC system and the air in your grow room. We’ll dive into proactive and reactive measures to achieve clean HVAC and air systems to prevent pathogens and pests and improve crop yields and quality.

Why HVAC/Air Sanitization is Vital

The air in your grow room is as important to successful and healthy crops as the surfaces and plant substrates. Keeping the air in your cannabis cultivation grow space sanitized and free of microbes, pests, and pollutants saves you time, energy, and money while improving plant health, reducing crop loss, and avoiding expensive and labor-intensive battles with microscopic invaders.

First, let’s take a look at the difference between sanitization and sterilization. Sanitization involves regular, surface-level cleaning, such as wiping up a spill, or cleaning tools. Sanitization is an integral part of the growing process and vital to regularly producing quality crop yields. Sterilization takes this approach to clean down to a microscopic scale, to rid a grow space of bacteria and microbes. Think of sanitization as wiping down a counter with a regular wet cloth, and sterilization as wiping the counter down with an antimicrobial wipe.

Now, to apply the sanitization/sterilization distinction to our subject of HVAC and air. You always want to keep your grow space as clean as possible, aiming for sterilization wherever viable. In reality, microbes exist in the fresh air, and the air we breathe out with every breath, so totally sterilizing your air is beyond the capacities of most growers. Focus on sterilizing the surfaces of your HVAC system, along with your surfaces and tools. Sanitization is a more achievable goal when it comes to your grow space air.

As with the other areas of sanitization we’ve examined in this series, failing to sanitize your grow space air or HVAC system can lead to adverse outcomes, such as:

  • Total crop loss
  • Reduced crop yield and quality
  • Increased spending on bactericides, fungicides or biologicals
  • Time/energy wasted on preventable issues
  • Bad publicity from products failing lab tests
  • Negative impact on the company and its brands’ reputation

The cannabis industry has become increasingly competitive, and this will only continue. It’s important to recognize that small investments in sanitization upfront can significantly minimize the risk of these costly events. If you’re part of a vertically integrated operation, these adverse outcomes can affect your entire supply chain, leading to further repercussions.

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How To Approach HVAC and Air Sanitization

To evaluate several critical things cannabis grow can do to maintain clean air and airways, we’ll look at both proactive and reactive measures. Proactive measures are routine cleaning activities, and investment in tools made to prevent any incidents. On the other hand, reactive measures are actions made in direct response to a sanitary problem after it has occurred.

Proactive Measures: Equipment

  • Regular Fresh Air Exchange: The ‘V’ in HVAC stands for ‘ventilation,’ which is crucial for your cannabis grow operation. Ensure that your ventilation system is sized correctly to exchange and circulate fresh air throughout your grow room and doesn’t miss any stagnant spots that can result in mold and mildew.
  • HEPA Filters: Cannabis growing conditions are often a breeding ground for unwanted contaminants. Using a high-quality HEPA filter helps your commercial grow operation thrive by ensuring air quality in the space is as clean of contaminants as can be.
  • Photo Catalytic Oxidation (PCO): PCO is an organic protection method against common crop pathogens. It allows growers to produce high-quality yields that align with regulations.
  • Multi-Cluster Ionization (MCI): MCI, kills molds, mildews, bacteria, and more using a Dielectric Barrier Ionizer (DBI). The ions that a DBI creates are more stable and powerful than those of competing technologies.
  • Probiotic Air Treatments: Another great way to keep your air sanitized is through probiotic air treatments. Probiotics are ‘good bacteria’ that promote healthy ecosystems and restore the natural balance that is difficult to maintain in indoor grow spaces.

Strategic Conditioned Air Supply: This air supply is used to ensure consistent environmental conditions throughout the grow cycle. Without it, short cycling can occur, and this leads to stagnant air and microclimate issues. Sterilization and purification are important, but the first line of defense is creating an environment un-conducive to pathogens in the first place. The air supplied from your HVAC system needs to be supplied and returned strategically, with the specific racking and plant layout considered.

Proactive Measures: Routine

Along with proactive measures, it’s important to develop a rigorous sanitization routine to catch issues before they spiral out of control. Your HVAC/air sanitization routine should include:

  • Regular Equipment Checks and Maintenance to ensure that your grow room ventilation system is working properly. If you find something out of order and can’t figure out a fix, call an HVAC maintenance professional, as things can turn for the worse quickly.
  • HVAC/Air Circulation System Maintenance on both a monthly and yearly basis. Monthly tasks include removing/replacing the filter, inspecting the finger guards and fan blades for debris, and wiping down the air mixing chamber with acetone. Annual tasks include cleaning out the entire duct runs, which is generally a two-person job.
  • Humidity Monitoring is important because mold and mildew thrive in humid conditions. Humidity is also a vital factor in the f quality and yield of a crop. Keeping humidity and temperature at optimal levels, relative to each other, will make a huge difference in your output. Investing in a quality hygrometer or other environmental sensors and alarms can keep tabs on your grow room’s humidity levels.
  • Surface Sampling informs you when your grow space air is contaminating the surfaces in your grow area. Companies like 3M offer kits that enable you to collect samples, prepare them for testing, and process the tests, to give you a quality snapshot of the microbial state on grow room surfaces.
  • Consistent Air Circulation: Without consistent circulation throughout your entire grow space, powdery mildew and botrytis will establish where there isn’t adequate air circulation. Providing consistent, laminar airflow will ensure a healthy canopy and prevent the spread of pathogens.
  • Pruning and Canopy Maintenance: All of these environmental strategies are only beneficial when paired with proper plant work. Pruning and canopy maintenance ensures that airflow and light can penetrate the canopy and eliminate stagnant air pockets, which is huge for pathogen control. Removing excessive plant material provides space in the canopy, and makes it easier to control humidity levels, as there is less leaf surface transpiring in the room.

Reactive Measures

Pest infestations or contaminant outbreaks are a near inevitability when it comes to growing cannabis, no matter how well you follow the above steps. That’s why it’s important to understand what to do when one occurs. If your grow room ventilation has been overrun by pathogens or pests, you should:

  • Isolate infected plants to slow the spread
  • Detect the source of the outbreak
  • Treat the issue using the proper remedies


If your grow space ventilation has failed, leading to a pathogen or microbe outbreak, many of the above proactive treatments will cleanse the infection source, such as PCO, MCI, and probiotic air treatments. Foliar treatments like ZeroTol, a ‘biosafe’ algaecide, bactericide, and fungicide, kill pathogens while preventing crop damage, but should be applied cautiously, especially late in flower.  In severe situations, it may be necessary to harvest early to avoid a total crop loss.


An excellent way to detect a pest outbreak is by laying fly strips around your grow space to indicate increased insect activity. Many other pests will be hard to spot without a trained eye. Identify the particular outbreak visually and then create a specific treatment plan. Several actions can help stop the spread of an outbreak, including:

● Removing excess soil moisture to prevent larvae from hatching
● Regular leaf checks to understand the outbreak scope
● Spraying your plant with hard water to dislodge insects
● Vacuuming your plants (with a weaker, handheld vacuum, to remove pests

The Sanitization Battle Continues

We hope this exploration into the fundamentals of sanitization and sterilization, from your grow room surfaces, plants and substrates, to your HVAC system and grow room ventilation system, has shown that your fight against contaminants is complex but winnable.

Whether you’re looking to begin a vertical grow operation, or just have a general question, contact Pipp Horticulture today. We’re always happy to help enthusiastic cannabis growers!

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