Understanding ASHRAE Standards 145.2 and 52.2: A Guide to Interpreting Air Purifier Performance

ASHRAE Standard 52.2 is the industry standard for evaluating performance of air-cleaning devices as a function of particulate size. It specifically focuses on the removal of particles ranging in size from 0.3 to 10 microns, including PM_2.5 and PM₁₀.

Key Considerations:

• Provides Minimum Efficiency Reporting Value (MERV) from 1 to 16 (higher is better).
• Measures efficiency across three particle size ranges: 0.3–1.0 µm, 1.0–3.0 µm, and 3.0–10.0 µm.
• Like 145.2, the test is performed in a controlled test duct at a defined airflow rate determined by the manufacturer.

Both ASHRAE standards measure efficiency at the airflow rate (CFM) the system is expected to operate under typical conditions. The airflow directly influences the results. Unfortunately, not all manufacturers test at the same airflow rate, nor do they consistently disclose this information.

Why airflow rate matters:

• Lower airflow results in higher removal efficiency, as contaminants spend more time in contact with the filter media.
• Higher airflow results in more volume of air cleaned at the cost of lower single-pass efficiency. A balance is needed between efficacy and throughput.
• Air purifiers operating at lower CFM will often report higher removal efficiencies yet may clean a smaller total volume of air over time.
• Conversely, a unit with a lower removal efficiency but higher airflow may deliver more total clean air per hour.
• To make apples-to-apples comparisons, look at efficiency and tested airflow, or even better, calculate the Cleaned Air Rate (CAR) if both values are provided: CAR = Efficiency (%) × Airflow (CFM)

For example:

• A purifier that removes 90% of a given contaminant at 500 CFM delivers 450 CAR.
• Another unit that removes 70% of the same given contaminant at 800 CFM delivers 560 CAR cleaning more air, faster, even with a lower efficiency rating.

When comparing different air purifiers, keep these tips in mind:

1. Verify the testing standards used: Make sure the product was tested according to recognized ASHRAE standards (such as 145.2 for gas-phase and 52.2 for particulate). Be cautious of self-defined standards that don’t provide meaningful or comparable data.
2. Ask for airflow rates used during testing: Without that, efficiency numbers are only part of the story.
3. Consider total performance: Pairing high-efficiency filtration with a smart operating system that balances airflow, pressure, and filter loading gives a better long-term solution.
4. Look at Cleaned Air Rate (CAR): Units with higher CFM often deliver higher CAR, meaning they can clean more air faster. This can reduce the number of units needed for a space, cutting costs on equipment, installation, and ongoing maintenance.
5. Match performance to your environment: Depending on the types of contaminants present, it may be more important to prioritize high removal efficiency for specific pollutants, such as formaldehyde, ozone, or PM2.5, rather than selecting the unit with the highest overall average efficiency.

The Indoor Air Quality Procedure, detailed in ASHRAE Standard 62.1-2022, allows facility managers and engineers to reduce outdoor air intake requirements if they can demonstrate that indoor contaminants of concern are controlled through filtration or other means.

To comply with IAQP, manufacturers and system designers must show that the air purification system installed can effectively control the contaminants listed in Table 6-5, such as PM_2.5, ozone, formaldehyde, and other VOCs. This is where third-party test data from ASHRAE Standards 145.2 and 52.2 becomes essential. These results are entered into the IAQP calculator to verify that indoor pollutant concentrations will remain below threshold levels as outdoor airflow is reduced.

By using IAQP and equipment tested to these standards, buildings can significantly lower their reliance on outdoor air. This results in major energy savings, reduced HVAC load, and fewer installed units, all while maintaining compliance with ventilation codes and protecting occupant health.

Understanding ASHRAE Standards 145.2 and 52.2 is essential for evaluating air purifier performance with real-world relevance. These standardized test methods support informed decisions, especially when using IAQP under ASHRAE Standard 62.1-2022 to reduce ventilation requirements. It is the manufacturer’s responsibility to have testing conducted by an independent laboratory to obtain credible, verifiable results. However, efficiency numbers alone don’t tell the full story. Always consider the airflow rate used during testing, the specific contaminants of concern in your space, and how the Cleaned Air Rate (CAR) aligns with your building’s needs. The goal isn’t just achieving high efficiency, but ensuring smart, effective air quality management that delivers measurable results in both occupant health and operational savings.

AirBox High-Volume Purifiers (HVPs) are engineered with these standards in mind. The AirBox HVPs are tested at real-world airflow rates and backed by third-party data to ensure reliable, code-compliant performance. Whether your facility requires high removal efficiency for specific contaminants or a high-CAR system to treat large volumes of air, AirBox offers solutions that align with ASHRAE Standards 145.2, 52.2, and the IAQP pathway. Each unit is paired with our Advanced Operating System (AOS), which intelligently manages airflow, pressure, and filter loading to maintain consistent performance over time. AirBox systems are built not just to meet performance claims on paper, but to deliver measurable results in the field. Thus, helping you improve indoor air quality, reduce energy consumption, and simplify compliance with ASHRAE.

To learn more about air purification testing and the specific requirements tied to these contaminants, check out ASHRAE’s Addendum g here.