This post discusses how to clean a grow tent using Ozone. Ozone is chemically represented with the formula 03. This additional oxygen atom makes ozone a powerful oxidant that destroys microorganisms and removes foul odors by oxidizing them. Ozone was approved for use by the FDA in 2003.

Ozone shock treatment is used in hospitals to sterilize operating rooms and medical equipment. In addition to hospitals it is also used in commercial food processing facilities to sanitize rooms after cleaning. More recently ozone has been used to sanitize N95 masks for front line workers fighting against COVID-19. Ozone is dangerous to breathe in so precautions must be taken to make sure you are not in the same room during operation.

I got into using ozone after moving into an old house that had overpowering second hand cigarette smoke in the master bedroom. Washing the walls with vinegar failed to remedy the problem, and the only real solution I kept finding online was using an ozone generator to neutralize the smell. It worked like a charm. A single 30 minute treatment was all that I need to get rid of the smell. I had a powerful new tool in my arsenal.

Ozone and Grow Tents

After spending $180 CAD on a ozone generator for a one-time use to get rid of cigarette smoke I started thinking about other potential uses. My hunting buddies mentioned running them in their trucks with all their hunting gear inside before deer season. Our extraction director mentioned he uses one to deodorize hockey gear.

These ozone generators kill all micro-organisms, mold, fungi and neutralize odor. What better way to clean a grow tent after a harvest is complete and all plants are out of the tent.

Which Ozone Generator To Buy

Grow tents and grow spaces are relatively small and will not require a large ozone generator. For anyone with a grow tent up to 4’x’4 I recommend getting a 5,000 mg/h Ozone Generator. If you are running larger 4’x8′ tents or have entire rooms to sanitize I recommend getting a 10,000 mg/h Ozone Generator.

When to Add Ozone to Tent

There are some websites that discuss using an ozone generator to sterilize plants prior to harvest. I WOULD NOT RECOMMEND this because terpenes are highly volatile compounds. The same odour removing properties of ozone would be a detriment to mature cannabis. The smells you worked so hard to cultivate would be neutralized by the strong oxidizing force of the ozone.

Ozone shock treatment should be done after harvest when plants are out of the tent. Even though I always seal the room and tent during ozone treatment I also try to do it when no one is home.

Cleaning vs Disinfecting/Santizing Grow Tent

Although this article is titled how to clean a grow tent, the true title should be how to “disinfect” or “sanitize” a grow tent. According to the CDC – Cleaning removes germs, dirt, and impurities from surfaces or objects. Cleaning works by using soap (or detergent) and water to physically remove germs from surfaces. Disinfecting kills germs on surfaces or objects. Disinfecting works by using chemicals to kill germs on surfaces or objects. This process does not necessarily clean dirty surfaces or remove germs, but by killing germs on a surface after cleaning, it can further lower the risk of spreading infection. Ozone treatment is a type of disinfection that should be done after cleaning. For cleaning I like to use alcohol based cleaners like lysol that can remove trichomes.

Steps to Clean a Grow Tent or Grow Box

1. Start by cleaning your grow space. Use water and detergent to remove plant matter and debris. Alcohol based cleaners should be used if there are trichome heads that need removal (e.g. if your plants were rubbing up against the side of the tent).
2. Remove all plants from the grow tent or grow box
3. Put anything else you want to sanitize in the grow tent (e.g. airstones, hydrotron, your DIY aeroponics cloner, foam collars, trimming shears etc.)
4. Turn off your exhaust fan. Oscillating fans can be left on to help circulate the air. The Ozone generator will have a small fan in it already to help move air around the metal plates but more circulation never hurts.
5. Run the Ozone generator for 30 minutes in your tent. The ozone generator should have a timer on it, if not you will need a light timer to run it. All the generators I have seen have timers.
6. After 2 hours enter room and turn on exhaust fan. Exit the room quickly until the fan has a chance to ventilate the room
7. After 12 hours you can re-introduce new plants into the space.

The room will smell fresh and new after the ozone treatment. Isn’t life grand when you do things the easy way.

Safety and Precautions

Precautions must be taken when using Ozone in a confined area as it is harmful to human health while being generated. The good thing about ozone is it’s unstable molecular nature (i.e., half-life of 22 minutes at room temperature). This means that it dissipates very quickly. Within 1 hour of the machine shutting off the room will be safe to re-enter, though I recommend waiting 4-6 hours to be extra cautious. You must not be in the same room as the ozone generator while it is running and if it is in an adjacent room the doors should be sealed off with painters tape.

If you are growing in a room that you sleep in, or you do not have exhaust that goes outside, I would exercise extreme caution when using an ozone generator. It bears repeating that you do not want to be in the same room as an ozone generator while it is running. If you are growing in a confined grow space you should likely stick to the old starsan or lysol wipe down to disinfect your tent or box. If you have roommates or friends coming over put up a sign to warn them not to enter the room.

Carbon Filter and Ozone Sterilization

A happy byproduct of the ozone sterilization method is that all the smells trapped in your carbon filter will be neutralized and oxidized away when you flush the ozone out of the grow tent. If you want to increase this effect you can run the exhaust fan during the last 10 minutes of the ozone treatment. This will not be as effective at re-activating carbon with steam tumbling but at the very least will remove existing odors from your carbon filter.

Why you need to Clean your Grow Tent

Your first grow may have gone so splendidly you may be wondering why you should even bother disinfecting your grow tent. The concern you should have is that a grow a tent/box becomes a petri dish for microbes. The plants grew alongside the concentration of microbes, and therefore were more likely to be resilient to any pathogens. Young plants will not be as resilient as mature plants; sticking them into a tent without disinfection can be a recipe for disaster. Sterilizing the room between grows is also more important for DWC growers who need to keep things sterile to mitigate the risk of root-rot.

Non-Ozone Sanitation

Startsan is a great substitute for those not wanting to use ozone. It is a contact acid-based foaming sanitizer that comes in a concentrated form. I add 15mL to every 2.5 gallon jugs of water. Use a spray bottle to spray down the walls and all other surfaces after cleaning with an appropriate cleaner. The premixed solution is good for weeks, even months if you use distilled water or your tap water is not too hard. You can test the solution with your pH meter, if you are below 3.0 you are good to go.