# What Is an Air Scrubber? How It Works, Uses and Sizing > What an air scrubber is, how HEPA filtration and air changes per hour work, how a scrubber differs from an air purifier and a negative air machine, and a four-step CFM sizing formula for commercial spaces. - **URL:** https://janitori.com/blogs/equipment-guides/what-is-an-air-scrubber **In this guide** - [What an air scrubber is](#what) - [How it works](#how) - [Scrubber vs air purifier](#purifier) - [Scrubber vs negative air machine](#negative) - [Where scrubbers are used](#uses) - [How to size one](#size) - [Mold and odors](#mold) - [Which unit fits which job](#pick) - [FAQ](#faq) An air scrubber is a portable machine that pulls room air through a stack of filters and blows the cleaned air back into the space. Facility crews, contractors and restoration teams use them to catch airborne dust, mold spores and fumes while work is under way. The word gets used loosely, and it is often mixed up with air purifiers and negative air machines. This guide separates the three, shows how to size a unit with simple math, and lists which of the units we sell suit which job. **Key takeaways** - An air scrubber is a portable multi-stage filter with a blower: it draws in room air, passes it through pre-filters and a HEPA filter, and returns cleaned air to the same space. - A scrubber recirculates air inside the room and needs no ducts. A negative air machine exhausts filtered air outside the space, which keeps the work zone at lower pressure than its surroundings. - Size by airflow: room volume times target air changes per hour, divided by 60, gives the CFM you need. Divide that by the unit's CFM rating to get the number of machines. - A scrubber filters the air only. It does not remove mold on surfaces, and the EPA says the cause of mold is a moisture problem that filtration cannot fix. ## What Is an Air Scrubber? An air scrubber is an air filtration machine that traps airborne contaminants such as dust, mold spores, virus particles and volatile organic compounds (VOCs). A United Rentals guide describes the cycle: the machine draws air in, filters it through multiple filters, and a blower sends the cleaned air back into the space. Portable units are used in construction, healthcare and industrial settings, and the guide says they can be used anywhere. A separate type of whole-home scrubber is built into a house's HVAC system, which is a different product from the portable machines on this page. ## How Does an Air Scrubber Work? An air scrubber works in stages, with each filter protecting the next. Coarse pre-filters catch large particles first, and a HEPA filter at the end captures the fine particles that get past them. Our [XPOWER X-2800](/products/xpower-x-2800-professional-3-stage-hepa-air-scrubber-550-cfm) shows the pattern. Its listing describes a washable nylon mesh filter, a pleated media filter and a 2.8 inch thick HEPA filter. The two pre-filters capture larger particles to extend the life of the HEPA stage, and the HEPA filter captures particles as small as 0.3 microns at an effective 99.97% rate. Some units add an optional activated carbon filter. The EPA notes that most filters are designed for either particles or gases, so a unit that must handle both needs a particle filter and a gas filter such as activated carbon ([EPA guide to air cleaners](https://www.epa.gov/indoor-air-quality-iaq/guide-air-cleaners-home)). The EPA also says all filters need regular replacement, because a dirty, overloaded filter will not work well. ## What Is the Difference Between an Air Scrubber and an Air Purifier? In everyday use there is little hard line: the Setra Systems blog calls an air scrubber or air purifier a portable filter that removes particles or other harmful elements from the air. Product listings use both words, so the name tells you little about the machine. The practical question for a facility buyer is airflow and build, not the name. Check the CFM rating, the filter stages and whether the unit can take ducting. Our listings rate job-site units from 550 to 2,000 CFM. The EPA's own consumer guide for portable air cleaners is written for homes and sizes units by clean air delivery rate (CADR), so do not use its room chart for a construction or remediation project. ## What Is the Difference Between an Air Scrubber and a Negative Air Machine? An air scrubber recirculates filtered air back into the room, while a negative air machine exhausts the filtered air outside the space. Setra Systems explains that pulling air in and sending it out of the room creates negative pressure, which limits the spread of harmful particles to people outside the contained area. A scrubber can be used as a negative air machine, but Setra says that takes added ducting, sealed housing and airflow adjustments. Some units are built with that in mind. The [XPOWER AP-2000](/products/xpower-ap-2000-portable-hepa-air-filtration-system-2000-cfm) lists a duct-able 12 inch exhaust outlet for negative pressure applications, and the [Novatek Novair 1000](/products/novatek-novair-1000-portable-hepa-air-scrubber-500-1000-cfm-f1000) is described as an upright negative-air machine with a 10 inch exhaust collar. ## Where Are Air Scrubbers Used? Air scrubbers are used wherever airborne dust, spores or fumes need to be controlled while people work or occupy a building. The United Rentals guide lists these common uses: - **Construction and demolition.** Controlling dust from drywall work, sawing, sanding and grinding, including silica dust from concrete, brick and tile work. - **Renovation in occupied buildings.** Keeping the air cleaner for occupants while work continues. - **Healthcare and manufacturing.** Supporting air quality protocols and capturing process contaminants. - **Remediation and restoration.** Clearing mold spores after flood damage, smoke after a fire, and contaminants from sewage or biohazard spills. - **Abatement.** Capturing materials such as asbestos, lead and mold during abatement projects. - **Odor reduction.** Minimizing lingering odors from paint or adhesives in enclosed spaces. After water damage, scrubbers are normally one piece of a drying setup. See our [air movers](/collections/air-movers) and [commercial dehumidifiers](/collections/commercial-dehumidifiers) for the equipment that handles moisture, which a scrubber does not. ## How Do You Size an Air Scrubber? Size an air scrubber by the air it must move: room volume times the target air changes per hour (ACH), divided by 60, gives the CFM required. The United Rentals guide gives this four-step method and says to confirm the result with an HVAC professional. - **Calculate the room volume.** Multiply length by width by height. A 40 by 30 foot room with 10 foot ceilings is 12,000 cubic feet. - **Pick a target ACH.** The guide cites 4 to 6 ACH for general construction, 6 to 12 ACH for mold, fire and water remediation, and 12 or more for hospitals and clean rooms. - **Convert to CFM.** Multiply the volume by the ACH and divide by 60. At 6 ACH, 12,000 cubic feet needs (12,000 x 6) / 60 = 1,200 CFM. - **Divide by the unit's rating.** With 600 CFM machines, 1,200 divided by 600 means two scrubbers. Two cautions from the United Rentals guide: an air scrubber reaches more air changes in a smaller space than in a larger one, and the guide says industry standards call for running a unit continuously for at least 24 to 48 hours at 4 ACH. Also check whether the listed CFM is rated with the filters installed: the Novair 1000 listing, for example, states 1,000 CFM with all filters installed and 500 CFM on low speed. ## Do Air Scrubbers Remove Mold and Odors? An air scrubber with a HEPA filter can capture airborne mold spores, but it does not remove mold growing on surfaces. United Rentals says scrubbers and plastic barriers help keep spores from spreading to other areas during remediation, and that scrubbers will not remove mold on surfaces. The EPA is direct on the cause: portable air cleaners do not address the cause of mold and musty odors, which is a water or moisture problem, and to solve it you remove the moisture source and clean up the mold. For smells, activated carbon is the filter that helps with strong odors from paint, solvents, adhesives, smoke and food, while HEPA filtration helps with smoke and dust odors. One more buying point: avoid machines that make ozone on purpose. The EPA states that no federal government agency has approved ozone generators sold as air cleaners for use in occupied spaces ([EPA on ozone generators](https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners)). HEPA scrubbers filter air mechanically and are a different product. ## Which Air Scrubber Fits Which Job? Match the unit's CFM and ducting to the job size. These four are listed in our catalogue, and the specs below are taken from their listings: | Unit | Airflow | Notable features from the listing | [XPOWER X-2800](/products/xpower-x-2800-professional-3-stage-hepa-air-scrubber-550-cfm) | 550 CFM | 3-stage filtration, 5-speed digital control, timer, PM2.5 air quality sensor | [XPOWER X-4700AM](/products/xpower-x-4700am-professional-3-stage-hepa-air-scrubber-750-cfm) | 750 CFM max | 3-stage filtration, GFCI outlets so units can be daisy-chained on one circuit, optional carbon filter | [Novatek Novair 1000](/products/novatek-novair-1000-portable-hepa-air-scrubber-500-1000-cfm-f1000) | 500 to 1,000 CFM | Upright negative-air design, two-speed motor, 10 inch exhaust collar, accepts HEPA or ULPA filters | [XPOWER AP-2000](/products/xpower-ap-2000-portable-hepa-air-filtration-system-2000-cfm) | 1,000 or 2,000 CFM | Two-speed switch, 12 inch duct-able exhaust outlet, casters, 25 ft power cord For the 12,000 cubic foot example above, one AP-2000 on its 2,000 CFM setting has the airflow for the 1,200 CFM target on paper, as do two 600 CFM class units. Browse the full range in our [air scrubbers collection](/collections/air-scrubbers). ## Frequently Asked Questions ## What does an air scrubber do? It pulls room air through pre-filters and a HEPA filter and returns cleaned air to the room, capturing dust, mold spores and other airborne particles. It filters the air only and does not clean surfaces. ## Is an air scrubber the same as an air purifier? The terms overlap, and Setra Systems uses them for the same kind of portable filter. Compare CFM, filter stages and ducting rather than the name. ## Do air scrubbers remove mold? They capture airborne mold spores when fitted with a HEPA filter. They do not remove mold on surfaces, and the EPA says the moisture source must be fixed and the mold cleaned up. ## How many air scrubbers do I need? Multiply room volume by target air changes per hour, divide by 60 to get CFM, then divide by the CFM rating of your unit. A 12,000 cubic foot room at 6 ACH needs 1,200 CFM, or two 600 CFM units. ## How long should an air scrubber run? United Rentals says industry standards recommend running one continuously for at least 24 to 48 hours at 4 air changes per hour. Follow the manufacturer's guidance for your unit and project. ## Related Equipment - [HEPA Air Scrubbers](/collections/air-scrubbers) - [Commercial Air Movers](/collections/air-movers) - [Commercial Dehumidifiers](/collections/commercial-dehumidifiers) [Shop HEPA Air Scrubbers](/collections/air-scrubbers)