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 how quickly portable air cleaners reduce key bioaerosols in an aerobiology test chamber.1,2,4
AHAM is an accredited standards development organization. Its performance standards provide 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 bioaerosol performance.1
The practical distinction is the type of evidence each standard provides. AC-1 addresses clean-air delivery for nonbiological particulate challenges. AC-5 addresses bioaerosol reduction, including changes in concentration and viability. Both standards may inform filtration efficiency discussions, but their results should not be combined into a single generic air-cleaner claim.3,4,8
What AHAM AC-1 shows
AHAM Verifide defines CADR as the volume of filtered air delivered by an air cleaner and reports separate scores for tobacco smoke, pollen, and dust. Within the AHAM framework, a higher CADR for a listed pollutant indicates faster filtration of that pollutant. AHAM's consumer guidance also uses CADR to help select an air cleaner for a given room size.3
EPA states that it does not certify, register, recommend, or publish lists of acceptable air-cleaning devices, although it identifies AHAM as one source of information. EPA also notes that AHAM's air-cleaner certification program is known as AC-1. For that reason, AC-1 evidence is generally described 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. It 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 is the smallest listed AHAM challenge particle.10
What AHAM AC-5 shows
AHAM's current AC-5 item page describes ANSI/AHAM AC-5-2023 as a method for measuring how quickly portable air cleaners reduce key bioaerosols in an aerobiology test chamber. The standard is intended to evaluate the ability of portable household air cleaners to reduce the concentration and viability of experimentally generated bioaerosols within a specified chamber.4
When AHAM announced the earlier AC-5 edition, it described the method as its first air-cleaner performance standard focused on microbiological pollutants, including viruses, bacteria, and mold. This purpose differs from AC-1. AC-5 applies when the study question concerns bioaerosol reduction rather than particulate CADR, room sizing, or CADR-to-watt efficiency alone.4,5,11
For compliance planning, AC-5 testing does not replace a review of the proposed claim language. EPA includes air purifiers, filters, and air treatment devices among examples of regulated devices when they claim to reduce microorganisms or purify the air. EPA also notes that HEPA filters limited to particle-size claims, without 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 buildings, existing buildings, and major renovations. It therefore provides a risk-mitigation framework for buildings and air systems, not a stand-alone certification program for air cleaners.6
ASHRAE Addendum a to Standard 241-2023 identifies ANSI/AHAM AC-1 and ANSI/AHAM AC-5 as consensus standards that may be used to determine air-cleaning effectiveness when the method is appropriate for the system and accepted by the authority having jurisdiction. The addendum also states that commercial and industrial in-room air cleaners using only mechanical fibrous filters determine equivalent clean airflow rate using ANSI/AHAM AC-1, adapted for nonresidential applications according to the specified 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