If you’ve ever stood next to an industrial plant at 2 a.m. and wondered why the hum of some machinery drowns out conversation while others barely register on a noise meter, you’re not alone. As an air separation unit (ASU) supplier, I get asked about noise levels all the time—especially by plant managers, engineers, and environmental health and safety (EHS) teams who have to comply with local noise regulations, protect worker hearing, or avoid disturbing nearby communities. The truth is, not all ASUs make the same amount of noise. The level depends on what type of unit it is, its size, how it’s designed, and what it’s being used for. Let’s break down the different types of ASUs and their typical noise profiles, based on years of working with facilities across manufacturing, healthcare, energy, and food and beverage industries. Type Of Air Separation Unit
First, let’s start with the most common distinction in ASUs: between cryogenic and non-cryogenic units. Cryogenic ASUs are the workhorses for large-scale oxygen, nitrogen, and argon production—think units that make hundreds of tons of gas per day for steel mills or chemical plants. They work by cooling air down to super low temperatures (below -180°C) to separate its components via distillation. Non-cryogenic units, on the other hand, use pressure swing adsorption (PSA) or membrane technologies to separate gases at higher temperatures, without the giant cold distillation columns. These are the go-to for smaller-scale or on-site applications, like a hospital needing 100 tons of oxygen a day or a food packaging plant needing nitrogen to keep chips fresh.
When it comes to noise, cryogenic ASUs tend to be noisier than non-cryogenic ones, but even within cryogenic units, there’s a huge range. Let’s start with small-scale cryogenic ASUs, usually for production under 100 tons per day. These are often used by smaller manufacturing facilities or as backup for non-cryogenic systems. From my experience, a compact skid-mounted cryogenic ASU for 50 tons of oxygen per day typically clocks in at around 85 to 90 decibels (dB) at 1 meter away for the main operating areas—like the compressor and distillation column skids. To put that in perspective, 85 dB is about as loud as a heavy city traffic truck passing by, and prolonged exposure without hearing protection can lead to damage over time. The main noise sources here are the air compressor, which is the heart of any ASU, and the expansion valves that control the flow of cold air through the distillation columns. Even small compressors for cryogenic systems generate a lot of vibration, which translates to noise, and these smaller units often have less built-in sound insulation than their larger counterparts.
Move up to mid-scale cryogenic ASUs, producing 100 to 500 tons of gas per day, and noise levels jump a bit—usually to 90 to 95 dB at 1 meter. These units are for medium-sized steel plants or fertilizer facilities, and their core components are bigger and more powerful. The main compressor here is often a centrifugal compressor, which is louder than the reciprocating compressors used in smaller cryogenic units, because it moves much more air at higher pressures. The distillation columns are also larger, and while they don’t generate a ton of noise on their own, the piping connecting them to the compressor and heat exchangers creates vibration that amplifies overall noise. I remember working with a mid-scale unit for a steel plant in the Midwest a few years back; their EHS team was initially worried about the 92 dB level at the plant perimeter, but after installing additional acoustic barriers around the compressor skid and wrapping piping with vibration-damping insulation, we brought that down to 82 dB, which was well within their local noise limits.
Large-scale cryogenic ASUs, producing over 500 tons of gas per day—some of the biggest in the industry, making thousands of tons for global chemical giants or large power plants—are the noisiest of all. Their noise levels at the compressor skid can hit 105 to 110 dB at 1 meter, which is about as loud as a chainsaw or a live rock concert. The main culprits here are the massive centrifugal compressors, which can weigh hundreds of tons and move tens of thousands of cubic meters of air per hour, and the pressure relief valves that release excess gas to prevent system damage. These units also often have large cooling towers that add to the noise load from water pumps and fan motors. For a plant located in a rural area, that 110 dB level might only be an issue for workers, but for units near residential areas or urban centers, this is a big challenge. I once consulted for a power plant in Europe that had a 1,200-ton-per-day cryogenic ASU; they had to build a 10-meter-high sound barrier around the entire unit compound and add acoustic enclosures to the compressor and cooling tower to bring perimeter noise down to 60 dB, which is roughly the level of normal conversation.
Now, shifting to non-cryogenic ASUs, which have grown a lot in popularity over the past decade because they’re cheaper to install for smaller applications and have lower energy costs. The two main types of non-cryogenic ASUs are PSA and membrane units, and their noise levels are much lower than even small cryogenic units. Let’s start with PSA ASUs, which are the most common non-cryogenic type for on-site oxygen and nitrogen production. PSA works by pumping air into beds of adsorbent material that traps nitrogen (for oxygen production) or oxygen (for nitrogen production), then flushing the bed with low-pressure gas to reuse it. A standard PSA unit for oxygen production, say 10 tons per day for a hospital or food plant, usually has noise levels of 60 to 70 dB at 1 meter. That’s roughly as loud as a normal office conversation or a quiet dishwasher running. The main noise sources here are the air compressor and the valves that switch the adsorbent beds between production and flushing. I’ve installed hundreds of these PSA units over the years, and most of my clients say that the noise is barely noticeable when you’re standing next to the unit—unless you get within a foot of the compressor, in which case it goes up to about 75 dB, still quieter than a vacuum cleaner. The nice thing about PSA units is that the adsorbent bed design is inherently quieter than cryogenic distillation, so even medium-sized PSA units (up to 100 tons per day) only hit 75 to 80 dB at 1 meter. That’s a big difference from mid-scale cryogenic units; for facilities that don’t need the super-high purity gas only cryogenic units can produce, PSA is a way to get the gas you need without the noise headache.
Then there are membrane ASUs, the newest type on the market, which use hollow fiber membranes to separate gases. Air is pushed through the membrane at high pressure, and oxygen or nitrogen passes through the fibers while the other gas stays on the other side. Membrane units are the smallest, simplest, and quietest type of ASU out there. A small membrane unit for lab use or small food packaging (like 500 cubic meters per hour of nitrogen) only makes 45 to 55 dB at 1 meter—about as loud as a quiet library or rustling leaves. Even larger membrane units, for up to 1,000 cubic meters per hour, top out at around 65 dB, which is quieter than a typical refrigerator. I recently worked with a craft brewery that switched from a small PSA unit to a membrane unit for their nitrogen packaging, and they commented that they could barely hear the new unit when it was running, unlike the old PSA which had a noticeable hum in their production room. The only downside of membrane units is that they have lower gas purity than cryogenic or PSA units, usually around 95% to 99% for nitrogen, so they’re best for applications where extremely high purity isn’t required.
Now, it’s important to note that these are all typical ranges, and noise levels can vary a lot based on specific design choices. For example, a cryogenic ASU with a sound-insulated compressor enclosure will be 5 to 10 dB quieter than one without, even if it’s the same size. For PSA units, some manufacturers use oil-free compressors instead of oil-lubricated ones, which are quieter and also better for applications like medical oxygen where oil contamination is a risk. For membrane units, the design of the pressure vessel and the type of membrane fibers can also affect noise levels—some newer membrane units use variable-speed fans that adjust noise based on production load, which is a big plus for facilities that don’t need full capacity 24/7.
Another factor that people often forget is distance from the unit. Noise levels drop off exponentially the further you get from the source. A 90 dB ASU at 1 meter is only about 60 dB at 10 meters, and 50 dB at 30 meters. That means that a noisy cryogenic unit might only be a minor concern for neighbors if it’s located far enough away from property lines. Also, regulatory requirements vary a lot by country and region. In the United States, OSHA requires that workers aren’t exposed to more than 85 dB for 8 hours a day, while the EU has a stricter limit of 80 dB for 8 hours. Local zoning laws also set limits on industrial noise at property lines, often between 50 and 65 dB depending on whether the area is residential, commercial, or industrial.
As an ASU supplier, my job isn’t just to sell the unit that produces the gas you need—it’s to make sure that unit fits your specific operational needs, including noise requirements. I’ve had clients come to me thinking they needed a cryogenic ASU, only to realize that a PSA or membrane unit would be cheaper, quieter, and more reliable for their application. A few years ago, a small medical supply company in Texas contacted me because their old cryogenic ASU was running at 92 dB inside their production room, and their workers were struggling with hearing fatigue. We swapped it for a 30-ton-per-day PSA unit, which clocks in at 72 dB at the same location, and they saved 15% on their energy costs too. That’s the kind of solution I care about—matching the right ASU to the right job, not just pushing the largest unit on the market.
If you’re in the market for an ASU, whether you’re a plant manager dealing with noise regulations, a hospital looking for reliable medical oxygen, or a food producer needing nitrogen for packaging, I can help you find the right fit for your needs. Every application is different, and the noise level is just one part of the equation—we’ll also consider purity requirements, production volume, energy costs, and maintenance needs. To discuss your specific needs and get a personalized recommendation, feel free to reach out for a consultation.
Cryogenic Liquid Storage Tank References
- Occupational Safety and Health Administration (OSHA). Noise Exposure Limits. U.S. Department of Labor.
- European Agency for Safety and Health at Work (EU-OSHA). Industrial Noise Prevention and Control.
- Air Separation Equipment Manufacturers Association (ASEMA). Cryogenic and Non-Cryogenic ASU Noise Profiles, 2022.
- World Health Organization (WHO). Environmental Noise Guidelines for Industrial Facilities, 2018.
- Process Industry Practices (PIP). Noise Control for Process Equipment, 2021.
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