A Practical Office Air Cleaning Plan Built Around Evidence Limits

Direct answer: An effective office air cleaning plan prioritizes ventilation—the introduction of outdoor air—as a primary method for managing indoor air quality (IAQ). Use the checks below to decide what to verify before buying, configuring, or citing the claim.

Who this is for

This is for readers evaluating A Practical Office Air Cleaning Plan Built Around Evidence Limits who need a practical decision path, clear caveats, and source links before acting.

Related reading path: pair this page with CADR room sizing and CO2 monitor calibration when the decision depends on setup details outside this article.

Quick decision check

Check	Why it matters	What to do next
Measurement target	CO2, CADR, MERV, and airflow measure different things and should not be swapped as if they were one metric.	Identify which pollutant or ventilation question the page is actually answering.
Room and system fit	Room volume, occupancy, noise, filter loading, and HVAC compatibility can change the practical answer.	Apply the guidance to the actual room or system before acting.
Evidence limit	Air cleaners, filters, and sensors can support a plan, but they do not guarantee health outcomes by themselves.	Use the cited source limits before making stronger claims.

An effective office air cleaning plan prioritizes ventilation—the introduction of outdoor air—as a primary method for managing indoor air quality (IAQ). Portable air cleaners and upgraded HVAC filters are intended to serve as supplemental tools to reduce particle pollution, rather than as replacements for adequate ventilation [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home]. While carbon dioxide ($CO_2$) monitors can be used to track ventilation effectiveness, $CO_2$ levels serve as an indicator of ventilation rates and do not directly measure the concentration of all indoor pollutants or particles [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation].

Technology Baseline: Components of an Air Cleaning Plan

A functional office air cleaning strategy relies on three distinct technological categories: filtration, supplemental cleaning, and monitoring.

1. HVAC Filtration

The building's Heating, Ventilation, and Air Conditioning (HVAC) system serves as the primary infrastructure for air movement. Upgrading filters within this system is a key strategy for improving IAQ.

• Function: To reduce the concentration of particles in the indoor air [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Implementation Requirements: Filters must be compatible with the existing HVAC system's capacity. The US EPA recommends upgrading to the highest efficiency filter that the system can support without compromising airflow [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Maintenance Implications: Effectiveness depends on proper fit and regular replacement to prevent bypass or reduced airflow.

2. Portable Air Cleaners

Portable air cleaners are supplemental devices intended for use where ventilation is difficult to manage or as an additional layer of particle reduction.

• Function: To capture particles from the air in specific zones [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].
• Performance Metrics: The effectiveness of these devices is determined by both capture efficiency and the rate of airflow, often measured in cubic feet per minute (CFM) or liters per second (L/s) [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].
• Constraint: These devices are not designed to remove $CO_2$ or other gases; they are designed for particle-based pollutants [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].

3. $CO_2$ Monitoring

Carbon dioxide ($CO_2$) monitoring serves as a proxy for assessing how well a space is being ventilated.

• Function: To provide information regarding the adequacy of outdoor air exchange [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation].
• Limitation: $CO_2$ levels do not provide a complete picture of all indoor air quality conditions, as they do not measure the presence of other pollutants or particles [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation].

4. Integrated Standards (ASHRAE 241)

Modern air cleaning strategies may align with ASHRAE Standard 241, which focuses on the control of infectious aerosols. This standard utilizes the concept of "equivalent clean airflow," which integrates the benefits of ventilation, filtration, and air-cleaning strategies into a single-metric approach for managing aerosol risks [https://www.cdc.gov/niosh/ventilation/faq/index.html].

Comparison Criteria for Office Air Cleaning Components

When selecting or auditing air cleaning components, facility managers should evaluate equipment based on the following structured criteria:

Component Name	Primary Function	Key Spec/Range Values	Compatibility Requirements	Maintenance Implications
HVAC Filters	Particle reduction in central air streams	MERV rating/Efficiency percentage	Must match system pressure drop/airflow capacity	Requires regular inspection for fit and replacement frequency
Portable Air Cleaners	Supplemental particle removal	CADR (CFM or L/s) and Capture Efficiency	Placement in areas with low ventilation	Periodic filter replacement and cleaning of intake grilles
$CO_2$ Monitors	Ventilation indicator	Parts per million (ppm)	Placement in occupied breathing zones	Sensor calibration and battery/power management

Evidence Limits and Scientific Uncertainties

A practical plan must account for the following scientific and technical limitations to avoid overestimating the capabilities of the installed technology.

The $CO_2$ Threshold Uncertainty

While $CO_2$ is a useful indicator for ventilation, there is no universal, evidence-based consensus on a single "safe" $CO_2$ threshold for all indoor environments. Research published in the *Journal of Exposure Science & Environmental Epidemiology* indicates that many indoor $CO_2$ guidelines lack a clear, unified evidence basis, making it difficult to establish one-size-fits-all limits [https://www.nature.com/articles/s41370-024-00694-7]. Therefore, $CO_2$ readings should be interpreted within the context of the specific building's ventilation design rather than as an absolute verdict on air safety [https://www.nature.com/articles/s41370-024-00694-7].

Distinction from Direct Air Capture (DAC)

It is critical to distinguish between consumer/office air cleaning and Direct Air Capture (DAC). The US Department of Energy describes DAC as a specific technology class designed to remove $CO_2$ from ambient air for climate and carbon-management purposes [https://www.energy.gov/science/doe-explainsdirect-air-capture]. Standard office air cleaners, including HEPA-based units, are not designed for this purpose and do not remove $CO_2$ gas from the environment [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].

The Proxy Limitation

Because $CO_2$ is a byproduct of human respiration, its concentration reflects the rate of air exchange. However, because it is not a particle, its presence or absence does not indicate the concentration of other indoor pollutants, such as volatile organic compounds (VOCs) or fine particulate matter ($PM_{2.5}$) [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation].

Technical Constraints and Engineering Limitations

When implementing an air cleaning plan, facility managers must navigate the physical and energetic constraints of the building's existing infrastructure. An upgrade in filtration efficiency is not a frictionless process.

1. The Airflow-Efficiency Trade-off

The primary constraint in upgrading HVAC filters is the relationship between capture efficiency and airflow. While higher-efficiency filters are more effective at capturing fine particles, they typically introduce a higher resistance to airflow, often referred to as pressure drop.

• System Compatibility: The US EPA advises that filter upgrades must be limited to the highest efficiency that is "compatible with the HVAC system" [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Operational Risk: If a filter is too restrictive, it can reduce the total airflow (measured in CFM or L/s) provided by the system, potentially undermining the ventilation strategy and the effectiveness of the air cleaning plan [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].
• Energy Implications: Increased resistance in the HVAC system can impact energy consumption. Energy conservation standards for air cleaners and related components are established to manage these efficiencies [https://www.energy.gov/sites/default/files/2023-03/air-cleaners-ecs-dfr.pdf].

2. Zonal Limitations of Portable Units

Portable air cleaners are subject to the physical layout of the office. Their effectiveness is not universal across a floor plan but is localized.

• Airflow Dependency: The utility of a portable unit is strictly tied to its ability to move air through its filter media. If the unit's airflow rate is insufficient for the volume of the room, the capture efficiency becomes secondary to the lack of air circulation [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].
• Placement Constraints: Unlike central HVAC filtration, portable units require strategic placement in "difficult to ventilate" areas to act as effective supplements [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].

Airflow Verification and Capacity Protocols

To ensure the air cleaning plan remains functional, the actual delivery of air must be verified against the design requirements of the space.

1. Verifying Air Exchange Rates

The effectiveness of both HVAC systems and portable units depends on the volume of air processed. Facility managers should verify that the airflow, measured in cubic feet per minute (CFM) or liters per second (L/s), meets the minimum requirements for the intended occupancy.

• HVAC Verification: Use anemometers or pitot tubes to check that the airflow through supply vents has not been significantly reduced by the installation of higher-efficiency filters [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Portable Unit Verification: Periodically check that the airflow (CFM or L/s) of portable units remains within the manufacturer's specified range, as clogged filters or dust-laden intake grilles can reduce the rate of air movement [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].

2. Managing Pressure Drop

As filters accumulate particulate matter, the resistance (pressure drop) increases. This creates a technical constraint: the facility manager must balance the desire for high-efficiency particle capture with the need to maintain energy-efficient airflow and prevent excessive load on the HVAC motor [https://www.energy.gov/sites/default/files/2023-03/air-cleaners-ecs-dfr.pdf].

Expanded Audit Framework: Structured Data Fields and Maintenance Logs

To move from a qualitative assessment to a quantitative audit, facility managers should capture the following data fields for every air cleaning component in the building. This data should be recorded in a centralized maintenance log to track the lifecycle of the equipment.

Audit Field	Data Type	Purpose	Source Context
Filter MERV/Efficiency %	Numerical	To track the level of particle capture capability.	US EPA
System Pressure Drop (Inches w.g.)	Numerical	To ensure the filter does not exceed the HVAC system's capacity.	US EPA, DOE
Measured Airflow (CFM/L/s)	Numerical	To verify that the air cleaning rate meets the room's requirements.	US EPA
$CO_2$ Baseline (ppm)	Numerical	To establish a ventilation benchmark for the specific zone.	US EPA
EPA Certification Status	Boolean (N/A)	To clarify that no EPA-certified list of manufacturers exists.	US EPA
Compliance with ASHRAE 241	Boolean	To assess alignment with aerosol control standards.	CDC/NIOSH

Maintenance Log Requirements

A robust maintenance log should include the following entries for every inspection:

• Date of Inspection: To track the interval between filter changes.
• Filter Replacement Date: To manage the lifespan of the media.
• Observed Airflow (CFM/L/s): To identify degradation in system performance.
• Visual Inspection of Fit: To document the absence of bypass gaps [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].

Practical Implementation Plan

To build a plan around these evidence limits, follow these implementation steps:

• Audit Ventilation Infrastructure: Determine the current outdoor air intake rates. Ensure the HVAC system is capable of supporting higher-efficiency filters without restricting the necessary airflow, measured in cubic feet per minute (CFM) or liters per second (L/s) [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Execute Filter Upgrades: Where possible, upgrade HVAC filters to the highest efficiency compatible with the existing system. Ensure that the filter fit is checked to prevent air from bypassing the filter media [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Deploy Supplemental Cleaning: In zones where ventilation is difficult to increase (e.g., enclosed meeting rooms), deploy portable air cleaners to assist in particle reduction [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Establish Monitoring Protocols: Use $CO_2$ monitors to identify areas of stagnant air or insufficient ventilation. Use these readings to trigger adjustments in ventilation rates or to identify where supplemental air cleaners are most needed [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation].

Claims to Avoid in Air Quality Management

To maintain the integrity of an air cleaning plan, avoid making the following unsupported or inaccurate claims:

• Avoid: "HEPA filters or portable air cleaners remove $CO_2$ from the office." (Fact: They are designed for particles, not gas removal).
• Avoid: "Installing air cleaners eliminates the need for outdoor air ventilation." (Fact: Air cleaners are supplements, not replacements).
• Avoid: "A $CO_2$ reading below [X] ppm guarantees the air is free of all pollutants." (Fact: $CO_2$ is only a ventilation indicator).

Update-Watch: Areas for Future Monitoring

Facility managers should monitor the following areas for updates to their air cleaning plan:

• ASHRAE Standard Updates: Watch for changes in the implementation of ASHRAE 241 and how "equivalent clean airflow" calculations may evolve.
• Filter Technology: Monitor advancements in filter efficiency that may allow for higher particle capture without increasing the pressure drop on HVAC motors.
• Sensor Accuracy: Track developments in low-cost $CO_2$ and particulate sensors to improve the reliability of real-time monitoring data.

Decision Logic Matrix: Trigger-Based Actions

An effective plan uses monitoring data to trigger specific operational changes. The following matrix outlines how to respond to different indoor air quality indicators.

Observed Indicator	Primary Implication	Recommended Action	Technical Constraint
Rising $CO_2$ Levels	Insufficient outdoor air exchange/ventilation [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation]	Increase outdoor air intake or mechanical ventilation rates.	Limited by the HVAC system's maximum intake capacity.
High Particulate Levels (Low Airflow)	Inadequate filtration or insufficient supplemental cleaning	Upgrade HVAC filters (if compatible) or deploy portable air cleaners [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].	Must not exceed the system's pressure drop limit [US EPA].
High Aerosol Risk (e.g., crowded spaces)	Increased risk of infectious aerosol transmission	Align strategies with ASHRAE Standard 241 for aerosol control [https://www.cdc.gov/niosh/ventilation/faq/index.html].	Requires integration of ventilation and filtration.
Stagnant Air (Low Air Movement)	Poor air distribution/circulation	Re-evaluate placement of portable air cleaners or adjust HVAC dampers.	Effectiveness depends on capture efficiency and airflow [US EPA].

Regulatory and Certification Clarifications

A common error in air quality management is the assumption of regulatory oversight or manufacturer certification.

The Role of the EPA

It is a misconception that the US EPA provides a registry of "approved" or "certified" air cleaners. The US EPA does not certify, register, or provide lists of acceptable air cleaners or specific manufacturers/sellers [https://www.epa.gov/indoor-air-quality-iaq/does-epa-certifyregister-or-provide-lists-acceptable-air-cleaners-or]. Facility managers should rely on technical specifications (such as MERV ratings and CADR) and compatibility with HVAC systems rather than searching for an EPA-annotable list.

Distinction from Carbon Management Technologies

As noted previously, the technology used for office air cleaning is fundamentally different from Direct Air Capture (DAC). While DAC is a specialized technology for removing $CO_2$ from the atmosphere to manage climate change [https://www.energy.gov/science/doe-explainsdirect-air-capture], office air cleaning focuses on the removal of particles and the management of ventilation-related indicators like $CO_2$ [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].

Advanced Monitoring and Response Protocols

To transition from a reactive to a proactive air cleaning plan, the following monitoring protocols should be established:

• $CO_2$ Trend Analysis: Rather than reacting to single high readings, monitor the *rate of increase* in $CO_2$. Rapid increases in $CO_2$ levels can indicate a sudden drop in ventilation effectiveness or an increase in occupancy that the current ventilation rate cannot support [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation].
• Filter Integrity Checks: Implement a schedule to check the fit of upgraded filters. Even high-efficiency filters are ineffective if air is allowed to bypass the media through gaps in the frame [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Verification of Supplemental Cleaning: Periodically measure the airflow (CFM or L/s) of portable air cleaners to ensure that dust accumulation on intake grilles has not significantly reduced the device's effectiveness [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home].
• Standard Alignment Audits: Periodically review the building's ventilation and filtration strategy against the evolving requirements of ASHRAE Standard 241 to ensure the plan remains aligned with modern aerosol control science [https://www.cdc.gov/niosh/ventilation/faq/index.html].

Variables that Alter the Effectiveness of the Plan

An air cleaning plan is not a static installation; its effectiveness is subject to several operational variables. Facility managers must recognize that the "assessment" of air quality in a specific zone can change significantly based on the following factors:

1. Changes in Occupancy Density

Because $CO_2$ serves as a proxy for ventilation, any change in the number of occupants in a space directly alters the $CO_2$ readings. A sudden increase in occupancy will lead to higher $CO_2$ concentrations, which may indicate a need for increased outdoor air exchange, even if the mechanical filtration (HVAC filters) remains unchanged [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation]. In these instances, the "risk" is not necessarily an increase in particles, but a decrease in the ventilation rate relative to the human-generated $CO_2$ load.

2. Implementation of ASHRAE 241 Metrics

The assessment of air cleanliness changes when moving from traditional ventilation-only models to the "equivalent clean airflow" approach found in ASHRAE Standard 241. Under this standard, the effectiveness of the plan is no longer measured solely by the volume of outdoor air, but by the combined impact of ventilation, filtration, and supplemental air cleaning [https://www.cdc.gov/niosh/ventilation/faq/index.html]. A facility manager must re-evaluate their "clean air" metric if they begin integrating portable air cleaners to meet these higher-level aerosol control standards.

3. Airflow-Efficiency Fluctuations

The effectiveness of the central HVAC strategy is highly sensitive to the physical state of the filters. If a higher-efficiency filter is installed that exceeds the system's pressure drop capacity, the resulting reduction in airflow (CFM or L/s) may inadvertently decrease the overall ventilation effectiveness of the building [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home]. Therefore, an assessment of "improved filtration" should be accompanied by a verification of "maintained airflow."

Operational Lifecycle and Maintenance Constraints

To prevent the degradation of the air cleaning plan, maintenance protocols must address the physical and energetic constraints of the technology used.

1. Filter Integrity and Bypass Prevention

The US EPA emphasizes that the effectiveness of upgraded HVAC filters is contingent upon proper fit [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19]. A primary maintenance constraint is the prevention of "bypass," where air leaks around the edges of a filter. Maintenance schedules must include physical inspections of filter frames and seals to ensure that the upgraded efficiency is actually being utilized by the air stream.

2. Energy and Pressure Drop Management

As noted by the US Department of Energy, energy conservation standards for air cleaning components are critical to managing the operational costs and mechanical strain of the building [https://www.energy.gov/sites/default/files/2023-03/air-cleaners-ecs-dfr.pdf]. As filters accumulate particulate matter, the resistance (pressure drop) increases. This creates a technical constraint: the facility manager must balance the desire for high-efficiency particle capture with the need to maintain energy-efficient airflow and prevent excessive load on the HVAC motor.

3. Sensor Calibration and Drift

For $CO_2$ monitoring to remain a reliable indicator of ventilation, the sensors must be subject to regular calibration. Because $CO_2$ is used as a proxy for ventilation adequacy, "sensor drift"—where a sensor's accuracy degrades overly time—can lead to a false sense of security regarding outdoor air exchange rates [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation].

Risk-Based Zonal Prioritization Framework

Rather than applying a uniform strategy to the entire building, an evidence-based plan should prioritize zones based on their inherent ventilation difficulty.

Tier 1: High-Priority Zones (Difficult to Ventilate)

These are areas such as enclosed meeting rooms, small conference pods, or windowless offices where increasing outdoor air intake via the HVAC system may be mechanically difficult or impossible [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].

• Primary Strategy: Deployment of portable air cleaners to provide supplemental particle reduction.
• Monitoring Focus: Frequent $CO_2$ monitoring to detect rapid accumulation of human-generated byproducts.

Tier 2: Standard Occupancy Zones

These are typical open-plan office areas with established HVAC distribution.

• Primary Strategy: Optimization of central HVAC filtration (upgrading to the highest compatible MERV rating) and ensuring consistent airflow [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19].
• Monitoring Focus: Periodic auditing of filter fit and system pressure drop.

Tier 3: Low-Occupancy/Transient Zones

These include hallways, lobbies, or storage areas with minimal human presence.

• Primary Strategy: Maintenance of baseline filtration through the central HVAC system.
• Monitoring Focus: Low-frequency monitoring, as the risk of $CO_2$-related ventilation failure is lower due to reduced occupant-driven $CO_2$ production.

***

FAQ

What should I measure first?

Measure the variable the article is about, then separate particle cleaning, ventilation, CO2 indication, and source control before deciding what to change. For this page, apply that answer to A Practical Office Air Cleaning Plan Built Around Evidence Limits.

Does one number prove the room is safe?

No. A single CO2, CADR, or filter rating needs room context, maintenance context, and source-specific limits. For this page, apply that answer to A Practical Office Air Cleaning Plan Built Around Evidence Limits.

What should I do after reading?

Use the checklist or table to choose the next practical step, then verify it against the cited public guidance. For this page, apply that answer to A Practical Office Air Cleaning Plan Built Around Evidence Limits.

Sources

• US EPA: Air Cleaners and Air Filters in the Home [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home]
• US EPA: Air Cleaners, HVAC Filters, and Coronavirus (COVID-19) [https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-hvac-filters-and-coronavirus-covid-19]
• CDC/NIOSH: Ventilation FAQs [https://www.cdc.gov/niosh/ventilation/faq/index.html]
• US Department of Energy: DOE Explains...Direct Air Capture [https://www.energy.gov/science/doe-explainsdirect-air-capture]
• US EPA: Can I measure carbon dioxide ($CO_2$) indoors to get information on ventilation? [https://www.epa.gov/indoor-air-quality-iaq/can-i-measure-carbon-dioxide-co2-indoors-get-information-ventilation]
• Journal of Exposure Science & Environmental Epidemiology: Carbon dioxide guidelines for indoor air quality: a review [https://www.nature.com/articles/s41370-024-00694-7]
• PubMed Central: Recommendations for ventilation of indoor spaces to even reduce COVID-19 transmission [https://pmc.ncbi.nlm.nih.gov/articles/PMC8363431]
• CDC: Ventilation in Buildings [https://archive.cdc.gov/www_cdc_gov/coronavirus/2019-ncov/community/ventilation.html]
• CDC/NIOSH: Improving Air Cleanliness | Ventilation [https://www.cdc.gov/niosh/ventilation/prevention/air-cleanliness.html]
• US EPA: Does EPA certify/register or provide lists of acceptable air cleaners or manufacturers/sellers? [https://www.epa.gov/indoor-air-quality-iaq/does-epa-certifyregister-or-provide-lists-acceptable-air-cleaners-or]
• Department of Energy: Energy Conservation Standards for Air cleaners [https://www.energy.gov/sites/default/files/2023-03/air-cleaners-ecs-dfr.pdf]
• PubMed Central: Air Cleaning Technologies: An Evidence-Based Analysis [https://pmc.ncbi.nlm.nih.gov/articles/PMC3382390]