How To Size an Air Scrubber for Your Facility

Every facility has its own air quality challenges, from persistent odors to harmful emissions. Understanding how to size an air scrubber for your facility is the first step toward solving these issues with precision. An air scrubber cleans the air; the right one will transform your workspace into a safer, more efficient environment. Let’s dive into the technical steps that make this possible.

Step One: Identify the Contaminants You Need To Control

Sizing a molecular air scrubber starts with chemistry, not square footage. Before you calculate airflow or room volume, you must define exactly what you are trying to remove from the air.

Particulate vs. Molecular Sizing

Most general-purpose air scrubbers found in restoration or construction are for particulates. They use HEPA filters to trap particles such as dust, mold spores, and silica. Sizing these units is relatively straightforward because it primarily concerns airflow and filter surface area.

However, industrial odor control requires molecular or gas-phase filtration. This process involves capturing gases and vapors that pass right through a standard HEPA filter. Sizing for molecular filtration is more complex because different gases interact differently with adsorption and absorption media. You are not just trapping a particle; you are facilitating a chemical reaction or adsorption or absorption (depending upon the type of media) event on the surface of a media bed.

Dwell Time and Media Volume

Different contaminants require varying contact times with the filtration media to be effectively removed. This duration is known as "dwell time."

For example, light commercial odors might be adsorbed quickly, whereas heavy H₂S concentrations in a wastewater lift station require longer exposure to the media bed. This means you cannot simply look at cubic feet per minute (CFM). You must consider how much media the unit holds and how long the air stays in that media bed.

Common Industrial Contaminants

Identifying the specific gas allows you to select the correct media blend. Common scenarios include:

Solvents, paints, and adhesives release compounds that require activated carbon with a high microporosity.
Hydrogen sulfide and mercaptans are prevalent here and used to require impregnated carbons. The impregnated carbons work through a chemical reaction rather than just adsorption. This reaction creates heat and the potential for a bed fire. A newer, better option is Darco H₂S catalytic carbon, from Norit Americas, which does not use chemical reactions. It has higher loading rates and eliminates potential media caused bed fires.
Laboratories often deal with acid gases or ammonia, necessitating specific chemically treated media.
Stored plastics or rubber can release low-level but persistent fumes that accumulate over time.

Accurately identifying the contaminant type and its approximate concentration provides the necessary foundation for all subsequent calculations.

Step Two: Calculate the Required Air Changes per Hour (ACH)

In a recirculating system, where air is scrubbed and returned to the room rather than vented outside, ACH is used to estimate the rate of contaminant reduction. It is not necessarily about meeting fresh air ventilation codes, which are distinct regulatory requirements. Instead, it measures how aggressively you are scrubbing the existing atmosphere.

General ACH Ranges

While every facility is unique, industry experience offers reliable baselines for sizing:

Light Commercial Odors: Aim for 4–6 ACH. This level is usually sufficient for general office areas or light storage where odors are nuisance-level rather than hazardous.
Industrial VOC Control: Target 6–12 ACH. Manufacturing floors or active processing areas typically fall into this range to keep concentrations below irritant levels.
High-Load Chemical Environments: Plan for 12+ ACH. In spaces with continuous, heavy generation of gases like H₂S, rapid turnover is essential to prevent accumulation.

It is important to remember that a higher ACH yields faster contaminant reduction but also increases energy consumption and noise. Sizing aims for the sweet spot where efficiency meets effectiveness.

The Calculation Formula

To determine the necessary airflow, use this formula:

Room Volume (Length × Width × Height in ft³) × Desired ACH ÷ 60 = Required CFM.

For example, a 10,000 cubic foot room requiring 6 ACH would need a unit capable of delivering 1,000 CFM. This CFM figure becomes your baseline for selecting hardware.

Step Three: Factor in Media Type, Media Volume, and Dwell Time

This stage is where industrial-grade commercial odor control separates itself from generic air cleaning. A unit might have a powerful fan, but without sufficient media, it will fail to control gas-phase contaminants.

Molecular scrubbers use media such as activated carbon or proprietary blends. This media acts as a sponge (or chemical reactor) for gases.

Why Volume Matters

Media volume is equally as important as airflow. A unit with a high CFM but a thin media bed will allow contaminants to pass through untreated (a phenomenon known as "blow-by.")

Service Life: More media means a higher total capacity for holding contaminants, resulting in longer intervals between maintenance.
Adsorption Efficiency: A deep media bed forces air to take a tortuous path, maximizing contact with the carbon surface.
Dwell Time: As mentioned previously, the air must linger in the media long enough for the reaction to occur.

Balancing Airflow and Media

If you push air too fast through a shallow bed, the dwell time drops, and removal efficiency plummets. Conversely, too little airflow means the room air isn't being processed fast enough to keep up with the generation rate.

Step Four: Consider the Facility’s Layout and Airflow Patterns

Mathematics provides a theoretical size, but physical reality dictates performance. The layout of your facility plays a crucial role in how effectively a scrubber operates. Spaces with high racking, heavy machinery, or partition walls can create "dead zones" where air stagnates, making it difficult for a single large unit to clean the air thoroughly.

Recirculating scrubbers offer flexibility by eliminating the need for ductwork. Strategically placing units near contaminant sources captures emissions before they spread. Positioning scrubbers in corners or along airflow paths can also create circulation loops, ensuring even air distribution throughout the space.

Step Five: Evaluate Contaminant Load and Process Emissions

Sizing an air scrubber requires understanding how contaminants enter the environment, whether through constant emissions, intermittent spikes, or steady off-gassing.

Continuous processes, such as manufacturing lines, demand robust systems to handle peak loads, while batch processes require flexibility to handle short-term spikes. High contaminant loads deplete media faster, leading to "breakthrough," where the media becomes saturated and ineffective.

Proper sizing ensures the media bed can handle the load efficiently, reducing replacement costs and preventing downtime.

Step Six: Account for Compliance, Safety, and Industry Standards

Recirculating scrubbers play a critical role in supplementing safety strategies by reducing hazardous gas concentrations and improving indoor air quality. Properly sized units help facilities comply with OSHA exposure limits, protect workers, and prevent odors from affecting neighboring properties. By maintaining consistent contaminant reduction, these systems ensure safe, compliant operations without compromising mandated ventilation requirements.

Choosing the right air scrubber is an investment in safety, efficiency, and compliance. Understanding how to size an air scrubber for your facility ensures you’re equipped to tackle even the toughest air quality challenges. With the right system in place, you can create a cleaner, healthier environment for everyone. Contact Industrial Odor Control today to find the perfect air scrubber solution tailored to your needs.