Start with the decision each standard answers
- AHAM AC-1 and AHAM AC-5
- In this article, AHAM AC-1 refers to the ANSI/AHAM standard for room-air-cleaner CADR and particulate performance. AHAM AC-5 refers to the ANSI/AHAM standard for assessing the reduction rate of key bioaerosols by portable air cleaners in an aerobiology test chamber.1,2,4
AHAM identifies itself as an accredited standards development organization. Its performance standards establish common methods for testing home appliances and reporting major performance attributes. For room air cleaners, AHAM lists ANSI/AHAM AC-1-2020 for CADR and ANSI/AHAM AC-5-2023 for bioaerosols.1
The practical distinction is particulate evidence versus bioaerosol evidence. AC-1 addresses clean-air delivery for nonbiological particulate challenges; AC-5 addresses bioaerosol reduction, including concentration and viability. Both may inform filtration efficiency discussions, but they should not be treated as support for the same generic air-cleaner claim.3,4,8
What AHAM AC-1 shows
AHAM Verifide describes CADR as the volume of filtered air an air cleaner delivers and reports separate scores for tobacco smoke, pollen, and dust. Under the AHAM framework, a higher CADR for a listed pollutant indicates faster filtration of that pollutant. AHAM's consumer guidance also uses CADR for room-size selection.3
EPA states that it does not certify, register, recommend, or publish lists of acceptable air cleaning devices, and it points readers to AHAM as one source of information. EPA also notes that the AHAM air cleaner certification program is known as AC-1. AC-1 evidence is therefore discussed as third-party performance verification, not EPA endorsement.9
CDC's ventilation FAQ treats CADR as a clean-air input for portable HEPA air cleaners and explains that AHAM labels report smoke, dust, and pollen CADR values. Of those values, CDC identifies smoke CADR as the most relevant to viral particles associated with respiratory diseases because smoke particles are the smallest listed challenge.10
What AHAM AC-5 shows
AHAM's current AC-5 item page describes ANSI/AHAM AC-5-2023 as a method for assessing how quickly portable air cleaners reduce key bioaerosols in an aerobiology test chamber. Its stated purpose is to evaluate the capability of portable household air cleaners to reduce the concentration and viability of experimentally generated bioaerosols in a specified chamber.4
AHAM's publication announcement for the earlier AC-5 edition described it as the organization's first air-cleaner performance standard focused on microbiological pollutants, including viruses, bacteria, and mold. AC-5 therefore serves a different study question from AC-1: bioaerosol reduction rather than particulate CADR, room sizing, or CADR-to-watt efficiency.4,5,11
For compliance planning, AC-5 does not eliminate the need to review claim language. EPA lists air purifiers, filters, and air treatment devices among regulated device examples when they claim to reduce microorganisms or purify the air. It also notes that HEPA filters limited to particle-size claims, with no air-purification or microorganism claims, are generally outside FIFRA device regulation.8
How ASHRAE 241 uses AHAM methods
ASHRAE describes Standard 241 as establishing minimum requirements intended to reduce disease-transmission risk from exposure to infectious aerosols in new and existing buildings and major renovations. The standard addresses risk mitigation at the building and air-system level, not certification of a stand-alone air cleaner.6
ASHRAE Addendum a to Standard 241-2023 includes ANSI/AHAM AC-1 and ANSI/AHAM AC-5 among the consensus standards permitted for determining air-cleaning effectiveness, provided the method fits the system and is accepted by the authority having jurisdiction. The addendum also addresses commercial and industrial in-room air cleaners that use only mechanical fibrous filters. For these devices, equivalent clean airflow rate is determined using ANSI/AHAM AC-1, adapted for nonresidential applications according to the stated chamber-size criterion.7
| Frame | What it shows | What it does not decide alone |
|---|---|---|
| ANSI/AHAM AC-1 | Portable room-air-cleaner CADR for particulate challenges such as smoke, dust, and pollen. | Bioaerosol viability, microorganism claim support, ozone safety, or installed HVAC performance. |
| ANSI/AHAM AC-5 | Bioaerosol reduction rate, concentration reduction, and viability reduction in a specified aerobiology chamber. | Particulate CADR room-size labeling, CADR-to-watt efficiency, or all public-health claim obligations. |
| ASHRAE 241 | A building and air-cleaning effectiveness framework for infectious-aerosol risk mitigation. | Product approval, EPA device compliance, or automatic acceptance of any one laboratory report. |
Scoping questions before testing
- Name the decision first: particulate CADR comparison, bioaerosol reduction, ASHRAE 241 equivalent clean airflow, EPA claim support, or engineering screening.3,4,7,8
- Define the product configuration: portable household room air cleaner, larger in-room commercial device, ducted HEPA unit, in-duct UV system, HVAC filter, or custom recirculating system.7,10
- Separate particle removal, filter efficiency, bioaerosol viability, ozone or byproduct safety, and energy-efficiency questions before writing the protocol.3,4,10,11
- Check whether marketing language reaches microorganisms, air purification, pathogen mitigation, or public-health outcomes, because those words can change the EPA device and evidence discussion.8,9