Posted in

Do ethylene scrubbers require special ventilation?

by sandra•

If you’ve ever stood in a produce loading dock at 5 a.m., watching crates of bananas or bell peppers get unloaded straight from a shipping container, you’ve probably noticed a small, underrated piece of equipment working behind the scenes: an ethylene scrubber. I’ve been in the business of building and servicing these units for 12 years now, ever since a small family-owned fruit distributor in Miami came to me frustrated that their shipment of organic avocados was rotting three weeks early, despite being stored in temperature-controlled rooms. Back then, I barely knew the ins and outs of ethylene oxidation, but that problem stuck with me—and it’s what led me to focus my entire career on making ethylene scrubbers work as hard as the facilities that rely on them. Over those years, I’ve gotten hundreds of questions from clients, new and long-term alike, and one that comes up more than any other is: “Do ethylene scrubbers require special ventilation?” It’s not a simple yes or no, and the answer isn’t just based on equipment specs—it’s based on how the scrubber is used, the space it’s in, and what you’re trying to protect. Let’s break this down, because getting it right isn’t just about keeping a unit running; it’s about saving you money, food, and years of stress. Ethylene Scrubber

First, let’s refresh what an ethylene scrubber actually does, because a lot of people mix it up with general air purification systems, and that confusion is where most of the ventilation questions start. Ethylene is a natural plant hormone that triggers ripening, blooming, and aging—what growers call “senescence.” For perishable goods like fresh produce, cut flowers, or even cured tobacco, even tiny concentrations of ethylene (as low as 0.1 parts per million, or ppm) can turn a profitable shipment into waste in a matter of days. Scrubbers work by pulling air from the storage space, passing it through a medium that binds or breaks down ethylene molecules, and then recirculating that clean air back into the room or facility. There are two main types of scrubbers most common in commercial use: carbon-based scrubbers, which use activated carbon to adsorb ethylene, and catalytic oxidizers, which use heat or a catalyst (like manganese dioxide) to break ethylene into CO2 and water vapor. Both do the same core job, but their chemical processes leave very different byproducts—and that’s a huge part of the ventilation conversation.

Let’s start with the easy case: catalytic ethylene oxidizers. This is the type we install most often for large-scale facilities, like 100,000-square-foot cold storage warehouses for bananas. The catalytic reaction I mentioned earlier, where ethylene is split into carbon dioxide and water, is pretty straightforward—once it’s running at its operating temperature (usually between 200 and 300 degrees Fahrenheit), there’s almost no toxic byproduct. But here’s the thing about heat: catalytic oxidizers draw in warm, ethylene-laden air, and exhaust that cooled, clean air back into the space. Wait, so why would that need ventilation? It has to do with airflow balance. If your cold storage facility is already maintaining a precise temperature—say, 58 degrees for cavendish bananas—you don’t want the oxidizer’s heat output to throw that balance off. If the oxidizer is pulling air out of the room and pushing it back without any make-up air coming in, you create negative pressure inside the room. Negative pressure means you’re pulling warm, humid outside air in through gaps around doors, loading docks, or vents, which then makes your refrigeration unit work overtime to cool that incoming air. That’s a huge waste of energy, and it can also create condensation on the produce crates, leading to mold. So for catalytic oxidizers, the “special ventilation” they need isn’t some fancy, dedicated exhaust system—it’s a properly sized make-up air vent. This is a standard part of most commercial HVAC designs, but it’s often overlooked when someone is adding a scrubber to an existing space. I once had a client in Atlanta who installed a catalytic oxidizer in a 15,000-square-foot flower cooler without adding make-up air. Within two weeks, their utility bill went up 22%, and they had to replace three pallets of roses that developed gray mold from condensation. We added two 12-inch make-up air vents on the opposite side of the cooler from the oxidizer’s air intake, and the issue was gone. The takeaway here: for catalytic units, special ventilation is about balancing pressure, not exhausting harmful fumes.

Now the second type: carbon-based ethylene scrubbers. These are smaller, more common for medium to small spaces, like a flower shop’s back cooler or a grocery store’s produce section. Activated carbon works by attracting ethylene molecules to the surface of the carbon, trapping them and removing them from the air. But here’s the catch: over time, the carbon gets saturated with ethylene, moisture, and other volatile organic compounds (VOCs) naturally present in produce, so it has to be replaced or regenerated. When it’s working, there’s almost no exhaust from a carbon scrubber—air goes in, ethylene sticks, clean air comes out. But the problem comes when that saturated carbon is being handled, or when the scrubber is placed in a space that’s too small to let it do its job. Wait, but why ventilation? Let’s talk about air exchange rates. I’ve seen too many small grocery stores try to use one carbon scrubber for their entire 10,000-square-foot produce section, without any cross-ventilation. The scrubber can only process so much air at a time—if you have a high volume of ethylene being released from ripe apples and unripe avocados stacked together, the carbon can’t keep up, and it starts to release the trapped ethylene back into the air. That’s called “breakthrough,” and it’s a disaster for produce shelf life. So for carbon scrubbers, the special ventilation isn’t about making up air—it’s about ensuring that the air in the space is moving past the scrubber enough that it can do its job. That usually means placing the scrubber near air handlers or using ceiling fans to create a gentle cross-flow, so no corner of the produce section has stagnant air where ethylene can build up. I had a grocery store client in Ohio who kept having to throw out bell peppers because they were ripening too fast in the back of the produce section. They had a small carbon scrubber near the front, but there was a big display of pumpkins blocking airflow to the back cooler. We moved the scrubber to the central aisle, added two 20-inch circulation fans at the ceiling, and the pepper shelf life jumped from 7 days to 18 days. No extra vents, no big construction—just simple ventilation that complemented the scrubber’s airflow.

But wait, there’s one scenario where both types of scrubbers absolutely do need special, dedicated ventilation: when they’re used in enclosed spaces that aren’t regulated for air quality. I once worked with a small cannabis cultivation facility in Colorado that was using carbon scrubbers to remove ethylene from their flowering rooms, but they had the scrubber exhaust directed straight into the same room. That’s a mistake I see all the time with small-scale operators. Even though carbon scrubbers don’t emit toxic fumes, the process of adsorbing ethylene releases a tiny bit of VOCs from the carbon itself, and over time, if that air isn’t exhausted out of the building, the concentration of those VOCs can build up. For cannabis operations, where air quality is tightly regulated for compliance, that meant they were failing their quarterly air quality tests. We installed a small, dedicated exhaust vent for the scrubbers, leading straight to the building’s exterior vent stack, and that fixed the issue. Another example: if you’re using a scrubber in a storage trailer that’s parked in a enclosed yard, not connected to any building ventilation. If you run the scrubber without a way to exhaust any small amounts of byproduct (even from catalytic units, which can occasionally emit trace amounts of CO if not calibrated correctly), you can create a buildup that’s a safety risk. In that case, special ventilation means a vent leading to outside air, not just recirculating within the trailer.

Now let’s get into the common myths around this question, because I’ve heard them all. The first big myth is that all ethylene scrubbers produce dangerous fumes that need heavy exhaust systems. That’s only true for poorly maintained units. If a catalytic oxidizer is serviced every 6 months—cleaning the catalyst, checking the temperature gauge, replacing any worn parts—it will only emit CO2 and water vapor, same as your own breath. The only time you get dangerous byproducts is when the catalyst is dirty, so it can’t fully break down ethylene, leading to trace CO emissions. The second myth is that ethylene scrubbers need ventilation that’s separate from your existing HVAC system. Again, that’s not true for most commercial spaces. If your HVAC system is already designed to circulate air and maintain pressure, adding a scrubber is just part of that system, not an add-on that needs its own custom ductwork. I’ve installed scrubbers in spaces where the HVAC system was already 10 years old, and we just tapped into the existing return air duct, added make-up air vents as needed, and didn’t have to modify the HVAC at all.

But here’s the most important point I’ve learned in 12 years of this work: the need for special ventilation depends entirely on the scale and layout of your space, and the type of scrubber you’re using. There is no one-size-fits-all answer, and that’s why so many clients get confused—they hear “ventilation is needed” or “don’t vent it” from different sources, and they don’t know who to trust. For the largest facilities, like multi-million-dollar cold storage warehouses, we work with their HVAC engineers to design a ventilation plan that integrates the scrubber, so pressure is balanced, energy use is minimized, and ethylene levels stay below 0.05 ppm (the threshold where produce stays fresh longest). For small spaces, like a retail flower shop, we recommend a small carbon scrubber paired with two circulation fans, no new vents needed. For enclosed spaces, like trailers or small grow rooms, we recommend a dedicated exhaust vent to prevent any buildup, no matter the scrubber type.

I’ve had clients argue with me at times, saying they’ve run a scrubber for years without any extra ventilation, and their produce is fine. Most of the time, that’s because they’ve gotten lucky—their space has natural airflow, or they’re not pushing the scrubber to its maximum capacity. But I’ve also had clients come to me after a year of that “lucky” setup, only to have a load of strawberries go bad because a heatwave made their coolers work harder, and the scrubber couldn’t keep up because airflow was stagnant. It’s the old adage: if something works, don’t fix it—until it doesn’t. And when it stops working, it’s usually not the scrubber’s fault—it’s the ventilation around it.

So what does that mean if you’re considering adding an ethylene scrubber to your facility, or you’re wondering why your existing one isn’t performing as well as it should? The first step is to do a quick audit of your space: how big is it? Is it temperature-controlled? What type of produce or goods are you storing (some, like citrus, release less ethylene than apples or bananas)? How many scrubbers are you using, and where are they placed? Then, look at the air flow: do you have stagnant corners? Is the pressure in the space consistent, or do you notice drafts around doors when the scrubber is running? For most facilities, the “special ventilation” the scrubber needs is simple, low-cost, and tailored to their existing setup, not some expensive, custom system.

At the end of the day, ethylene scrubbers are tools—no different than a forklift or a refrigeration unit. They work best when they’re matched to the space they’re in, and that includes the air flow and ventilation around them. I’ve seen too many facilities throw money at the fanciest scrubber on the market, only to have it underperform because they skipped the simple step of checking their ventilation. I’ve also seen small, modestly priced scrubbers extend produce shelf life by 50% just because they were paired with good airflow. That’s why I never give a generic answer when someone asks if ethylene scrubbers need special ventilation. I ask them to send over a floor plan, tell me what they’re storing, how big their space is, and what kind of problems they’re having. Because the right ventilation for your scrubber is specific to you, not the guy down the street who uses a different setup.

If you’re ready to talk through what your specific space needs, or you have questions about making your existing scrubber work better, we can walk through every step with you. There’s no one-size-fits-all, but there is a solution that will work for your facility, and it starts with understanding how your scrubber and your ventilation work together.

Oxygen Adsorbers References

  1. USDA Agricultural Marketing Service. (2021). Ethylene Management Guidelines for Perishable Produce Storage Facilities.
  2. ASHRAE. (2020). Chapter 21: Refrigerated Food Storage. ASHRAE Handbook—HVAC Applications.
  3. Van de Poel, B., et al. (2018). Ethylene Scrubbing Technologies for Postharvest Fresh Produce: A Review. Postharvest Biology and Technology, 145, 106-118.
  4. National Institute for Occupational Safety and Health (NIOSH). (2019). Safety Guidelines for Catalytic Oxidation Systems in Commercial Storage Facilities.

Yantai Keda Zhixian International Trade Co., Ltd.
As one of the leading manufacturers and suppliers of ethylene scrubber in China, we have world-leading production equipment and strong manufacturing capabilities. Please feel free to buy high-grade ethylene scrubber for sale here from our factory.
Address: No.18-2, Wuhan St, Yantai ETDZ, Yantai, Shandong, China
E-mail: ytkeda2026@163.com
WebSite: https://www.kedacastorage.com/