Certifications, Classifications, and Standards in Air Filtration

Created by Yasar Kiyak | |   Thermal Bonded Nonwoven

In the realm of air filtration and ventilation, various certifications, classifications, standards, and guidelines play crucial roles in ensuring safety, efficiency, and indoor air quality across different settings. From testing the fire resistance of air filter units to establishing protocols for evaluating the performance of gas-phase air-cleaning devices, these standards and guidelines provide the framework for manufacturers, designers, and regulators to uphold rigorous quality and safety standards. In this overview, I briefly discuss certifications, classifications, and standards, exploring their significance, scope, and implications for ensuring clean and healthy indoor environments, mostly focusing on filter efficiency. Let's delve into the intricacies of each aspect to gain a deeper understanding of their role in promoting safety, comfort, and well-being in built environments.


Ø UL900 Standard for Air Filter Units

UL 900 is a standard established by Underwriters Laboratories (UL) within the United States. UL 900 outlines the requirements for the construction, performance, and testing of air filter units used in various HVAC (Heating, Ventilation, and Air Conditioning) systems. This standard specifies the fire resistance of air filters to ensure their reliability and effectiveness in removing airborne particles from the air. Compliance with UL 900 helps manufacturers demonstrate that their air filter units meet recognized safety and performance standards, providing assurance to consumers and regulatory authorities.


ULC 111 is a standard established by the Underwriters Laboratories of Canada (ULC). This standard outlines the procedures for conducting fire tests on air filter units to assess their fire resistance and safety. The tests described in ULC 111 evaluate the performance of air filter units when exposed to fire conditions, including heat, flames, and smoke. The standard specifies criteria for measuring parameters such as flame spread, smoke generation, and structural integrity during the fire test. Compliance with ULC 111 helps ensure that air filter units meet minimum safety requirements and can withstand fire incidents without posing a hazard to occupants or property.

Classifications of air filtration products

Ø ISO 16890: Air filters for general ventilation

ISO 16890 is a global standard that outlines the examination and classification of air filters utilized in general ventilation systems. ISO 16890 outlines procedures for evaluating the efficiency of air filters in capturing particulate contaminants from the air. This standard introduced a new classification system based on the filter's efficiency in capturing particles of various sizes, including coarse, ePM10, ePM2.5, and ePM1. ISO 16890 replaced the previous European standard EN 779:2012 and aims to provide more accurate and reliable information about the performance of air filters. It helps users make informed decisions when selecting filters for their ventilation systems to ensure better indoor air quality and protect the health and well-being of occupants.

Ø EN 1822 and ISO 29463

EN 1822 and ISO 29463 are both standards that deal with high-efficiency particulate air (HEPA) filters and ultra-low penetration air (ULPA) filters, but they differ in their scope, testing procedures, and classification systems. EN 1822: This European standard specifies the testing and classification of HEPA and ULPA filters. It outlines procedures for evaluating the efficiency of these filters in removing airborne particles from the air and provides a classification system based on their efficiency. ISO 29463: This international standard also addresses the testing and classification of HEPA and ULPA filters. However, it provides more comprehensive guidelines, including aerosol production methods, measuring equipment requirements, and statistical methods for particle counting.

Ø ANSI/ASHRAE 52.2-2017

This standard outlines the testing method for evaluating the efficiency of general ventilation air-cleaning devices in removing particles of various sizes from indoor air. It provides procedures for determining the Minimum Efficiency Reporting Value (MERV) rating of air filters, which is commonly used to assess their effectiveness in capturing airborne particles.

Ø NIOSH-42 CFR84 Respirator Certification: Nonpowered Air-Purifying Particulate Respirators.

NIOSH-42 CFR84 refers to a specific testing method conducted by the National Institute for Occupational Safety and Health (NIOSH) for evaluating the filtration efficiency of respirator filters. The NIOSH-42C FR84 test assesses the performance of respirator filters in removing particulate matter from the air, including aerosols, dust, and other airborne contaminants. This test method is often used to determine whether respirator filters meet the filtration efficiency requirements specified by NIOSH standards, such as N95, N99, or N100 respirators, which are commonly used in healthcare, industrial, and occupational settings to protect workers from respiratory hazards. Compliance with NIOSH-42C FR84 ensures that respirator filters provide adequate protection against airborne particles, contributing to the safety and well-being of users.

Ø ASTM F3502-21: Standard Specification for Barrier Face Coverings

ASTM F3502-21 outlines the requirements and specifications for barrier face coverings, including cloth masks, non-medical face masks, and other similar devices. This standard provides guidelines for the design, construction, materials, performance, and labeling of barrier face coverings intended for use by the general public or in non-healthcare settings. Compliance with ASTM F3502-21 helps ensure that barrier face coverings meet recognized quality and safety standards, providing users with confidence in their effectiveness in reducing the transmission of respiratory droplets and airborne particles.


Ø ANSI/ASHRAE Standard 62.1-2022: Ventilation and Acceptable Indoor Air Quality

ASHRAE Standard 62.1, for non-residential, outlines the criteria for achieving and sustaining acceptable indoor air quality (IAQ) in various commercial, institutional, and industrial settings. It offers guidance on air purification and filtration methods to reduce both particulate and gaseous pollutants. Although primarily focused on HVAC and ventilation systems rather than industrial dust collection, the principles within the standard can be applied more broadly to industrial air filtration. This involves setting minimum efficiency requirements for air filters, typically measured using MERV ratings, which can inform the selection of cartridge filters in industrial dust collection systems. It's important to consider ASHRAE standards alongside other regulations like OSHA Permissible Exposure Limits (PELs) for industrial air pollutants. To ensure optimal IAQ, the standard mandates the use of air filters with a Minimum Efficiency Reporting Value (MERV) rating of at least 8. However, specific applications or regions with elevated pollutant levels may necessitate a higher MERV rating. Regular filter maintenance is also essential for preserving IAQ and maximizing system efficiency. For instance, in buildings situated in areas where the national standard or guideline for Particulate Matter Smaller than 2.5 Micrometers (PM2.5) is surpassed, measures must be taken to clean outdoor air before it enters occupied spaces. This involves the installation of particle filters or air-cleaning devices. These filters or cleaners must have a minimum efficiency reporting value (MERV) of at least 11, as rated according to ASHRAE Standard 52.2.

Ø ANSI/ASHRAE Standard 62.2-2022 Ventilation and Acceptable Indoor Air Quality in Residential Buildings

This standard is centered on ventilation and ensuring acceptable indoor air quality (IAQ) within residential buildings. It offers guidelines for ventilation rates, air exchange, and filtration systems to guarantee that residents have access to clean and healthful indoor air. For mechanical systems supplying air to dwelling units through ductwork exceeding 10 ft (3 m) in length and passing through a thermal conditioning component (excluding evaporative coolers), a filter with a designated minimum efficiency of MERV 11 or higher is mandated, as assessed according to the procedures outlined in ANSI/ASHRAE Standard 52.2. A new addendum proposed in late 2023 aims to elevate the minimum filter rating, requiring a qualifying filter of approximately MERV 13 or higher.

Ø ANSI/ASHRAE Standard 145.2-2016: Laboratory Test Method For Assessing The Performance Of Gas-Phase Air-Cleaning Systems: Air-Cleaning Devices

ASHRAE Standard 145.2 outlines a comprehensive laboratory test procedure for evaluating the effectiveness of gas-phase air-cleaning devices equipped with sorptive media. Here, "sorptive media" refers to the active component of the air cleaner, whether in granular, sheet, or pleated form, which functions by adsorbing and/or chemically or physically reacting with contaminant gases. This standard establishes laboratory test methods for assessing the effectiveness of such devices in removing contaminants from indoor air.

This testing occurs under consistent conditions with heightened gas concentrations, compared to typical ventilation scenarios. As a result, the purpose of the test is to compare the performance of different devices rather than precisely predict their effectiveness in specific applications.

Ø ANSI/ASHRAE/ASHE Standard 170:nbsp; Ventilation of Health Care Facilities

ASHRAE Standard 170 focuses on ventilation for healthcare facilities. It covers various aspects including air exchange rates, filtration, temperature control, and humidity levels to ensure the health and safety of patients, staff, and visitors within healthcare settings. The minimum filter MERV requirement varies depending on the specific application within the facility. Generally, the standard specifies MERV 14 as the minimum requirement for areas such as operating rooms, transplant operating rooms, and airborne infection isolation rooms. The standard suggests minimum filter efficiencies for various medical applications as follows: MERV 8 for nursing, MERV 14 for procedure rooms and delivery rooms, and MERV 16 for operating rooms.

The filtration specifications for operating rooms, cesarean delivery rooms, and Class 3 imaging rooms have been elevated from MERV 14 to MERV 16. In particular, Class 3 imaging rooms or operating rooms assigned for orthopedic procedures, transplants, neurosurgery, or dedicated burn unit procedures are now required to incorporate HEPA filters at the air terminal device. Again, note that different spaces have different minimums so please refer to the standard for a full discussion.

The latest addition to the 2021 edition of the standard drew from insights gained during the COVID-19 pandemic. It introduced a method allowing the exhaust from airborne infection isolation (AII) rooms to merge with general exhaust, provided it passes through a HEPA filter beforehand. This adjustment offers owners more flexibility in deciding how to manage AII room exhaust in new constructions and enhances confidence that regulatory authorities will endorse this approach for existing facilities.

Ø ANSI/ASHRAE/ICC/USGBC/IES Standard 189.1 International Green Construction Code

ASHRAE Standard 189.1 stands as a pivotal document in the realm of green building design and construction. This standard provides comprehensive requirements for the design, construction, and operation of high-performance green buildings, with a focus on sustainability, energy efficiency, water conservation, indoor environmental quality, and site development. ASHRAE 189.1 is intended to be adopted as part of building codes and regulations by jurisdictions at the international, national, state, and local levels to promote environmentally responsible building practices.  Unlike voluntary standards like LEED, Standard 189.1 is designed for adoption by various code jurisdictions, ensuring its widespread application. By aligning with LEED certification requirements, it streamlines the process for achieving sustainability goals, potentially increasing the adoption of both standards. With its evolution driven by consensus among industry experts, Standard 189.1 incorporates advanced strategies for indoor air quality. In Feb 2024, the proposed addendum to ASHRAE Standard 189.1 suggests changing the particulate matter removal requirement from referencing MERV-13 to MERV13A. The impact of this addendum on building operating costs is anticipated to rise, although the extent of this increase remains uncertain.

Ø ASHRAE 241 Control of Infectious Aerosols

ASHRAE Standard 241 represents a groundbreaking development as the first code-enforceable indoor air quality (IAQ) standard devised specifically to mitigate the indoor transmission of infectious aerosols. This standard, crafted with insights from the ASHRAE Epidemic Task Force, outlines requirements for numerous facets of air system design, installation, and operation. Standard 241 establishes the minimal clean air prerequisites necessary to curtail airborne diseases within commercial settings like offices, schools, and hospitals, as well as residential environments such as senior assisted-living facilities during heightened risk periods.

Prior to implementing Standard 241, compliance with ASHRAE 62.1 requirements is mandatory. Currently, standard 241 mandates a minimum MERV11 air filter. It is going to require minimum MERV-11A rating air filters starting on 1/1/2025 to take credit. You can take a look at my recent article about standard 241 for more details.


Filtration stands as a critical stage in the air treatment process within air conditioning systems, serving various purposes from preventing dirt buildup on coils to retaining particles that could cause short circuits in microprocessor manufacturing or contamination during surgical procedures. The effectiveness of filtration is determined by its Minimum Efficiency Reporting Value (MERV), ensuring particle retention efficiency according to specific application needs. A higher MERV rating signifies increased efficiency in removing particles. Filters lacking a MERV grade cannot be deemed equivalent to MERV-rated filters. Although filters with high MERV grades may incur higher costs, substituting them with non-rated filters can lead to legal issues, compromise production, and pose potential risks to human life depending on the application. Thus, ensuring proper filtration is paramount for maintaining good indoor air quality.

Please note that this article does not discuss all standards and certifications. Some local and federal agencies may have their own guidelines and regulations regarding filtration and ventilation. For instance, as of May 2023, CDC revised the minimum filter recommendation to MERV 13 to ensure improved filtration efficiency, where compatible with your HVAC system.  AHSRAE’s recommendation for HVAC systems, in general, advocates for the utilization of filters with a MERV of 13. However, the selection should be made considering the capabilities of the HVAC systems. Generally, augmenting filter efficiency results in heightened pressure drop, which may diminish airflow through the HVAC system, increase energy consumption by the fan to counteract the augmented resistance, or both. In cases where accommodating a MERV 13 filter is unfeasible, opt for the highest MERV rating feasible. Likewise, EPA has similar guidelines regarding filters and ventilation. MERV 13 or equivalent filters are required for heating/cooling systems and ventilation for residential in the state of California per Title 24. However, the filtration prerequisites are not applicable unless there is a minimum of 10 feet of duct connected to the unit.

ASHRAE standards are under continuous maintenance, meaning an ongoing process of updating and revising these standards to ensure they remain current and reflective of the latest advancements, technologies, and best practices in the fields of heating, refrigeration, air conditioning, and ventilation. This process involves regular review and consideration of proposed changes, additions, or deletions to existing standards based on new research, developments in the industry, feedback from related organizations, and emerging needs or challenges.  Once approved, these updates are incorporated into the standards through addenda, ensuring that ASHRAE standards remain relevant and effective in promoting safety, efficiency, and sustainability in HVAC&R systems. This article shows that, recently, there have been a lot of updates regarding the minimum filter requirements and recommendations.

In conclusion, understanding air filtration standards, classifications, and certifications is crucial for ensuring optimal indoor air quality and the safety of occupants in various environments, from residential buildings to healthcare facilities. By adhering to these standards and certifications, interested parties can make informed decisions to safeguard indoor air quality, promote health and well-being, and meet regulatory requirements for building design, construction, and operation.

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