Clean Air Delivery Rate (CADR) Testing

Aerosol Science

We use controlled aerosol generation and real-time particle monitoring in ANSI/AHAM AC-1-aligned chamber tests to calculate CADR at each speed setting.

Purpose & when to use

Clean Air Delivery Rate (CADR) testing measures how quickly a room air cleaner removes particles under controlled chamber decay conditions aligned with ANSI/AHAM AC-1. Optical Particle Counters (OPC) and Condensation Particle Counters (CPC) track concentration decay for smoke, dust, and allergen surrogates. Testing also aligns with ISO 29462 and ASHRAE 52.2 within our ISO 17025 quality system:

Benchmarking portable room air purifiers for marketing claims — speed-specific CADR under ISO 29462 supports product comparisons across smoke, dust, and allergen surrogate types.
Quantifying performance by fan speed or operating mode for air purifier design decisions — ISO 29462 decay curve fitting connects mode-level CADR to filter and fan trade-off analysis.
Linking filter media efficiency to whole-device air cleaning — ASHRAE 52.2 framing pairs [filtration efficiency data](/testing-services/particle-aerosol-measurement/filtration-efficiency/) with system-level CADR for integrated product programs.
Verification testing for retail claims on whole-room and large air cleaners — ISO 29462 chamber decay protocol provides a defensible and reproducible comparative basis for product documentation.
Performance drift assessment for filter loading and aging on in-duct and consumer devices — ASHRAE 52.2 particulate efficiency framing documents removal rate changes with service life.

CADR testing supports decisions based on particle removal rate, performance at specific speed settings, or comparative benchmarking. Applications include portable room purifiers, whole-room systems, and in-duct commercial air cleaners that require chamber decay characterization.

Air-treatment and room air-cleaning device families

CADR testing applies to room air-cleaning devices where particle removal rate is the primary performance claim — from portable units rated under ANSI/AHAM AC-1 to whole-room and in-duct systems requiring fit-for-purpose chamber decay characterization.

Room air purifierPortable room air cleaners
Whole-room cleanerHigh-capacity whole-room units
In-duct air cleanerCommercial HVAC in-line units
Fan-filter boxDIY and modular filter boxes

Instrumentation & measurement ranges

We select the measurement platform based on the surrogate aerosol, target particle size range, and applicable decay method. Each combination is defined during study planning and documented in the final report.

0.3 – 10 µmoptical

Optical Particle Counter (OPC)

Size-resolved number concentration — primary monitor for AHAM-aligned chamber decay studies tracking smoke, dust, and allergen surrogate removal in real time.

0.01 – 1 µmoptical-condensation

Condensation Particle Counter (CPC)

Total particle number concentration for ultrafine and fine surrogate fractions — selected when sub-micron sensitivity or fine-mode decay characterization is required.

11.5 – 30 m³chamber-volume

AHAM-aligned test chamber

Controlled test volume with defined mixing fan placement, sampling port geometry, and background decay characterization — sized to match the ANSI/AHAM AC-1 method intent.

0.1 – 10 µmgenerated-particle

Aerosol generation system

Controlled injection of smoke, dust, and allergen surrogates to reach target starting concentrations — lot-tracked surrogate materials with documented generation settings per run.

Test method options

Method	Strengths	Tradeoff	Aligned with
ANSI/AHAM AC-1 chamber decay CADR (primary standard)	Speed-specific CADR for smoke, dust, and allergen surrogates under ISO 29462 — the air purifier benchmark for defensible performance claims. Background decay characterization isolates device contribution; surrogate lot tracking and replicates satisfy quality-system and marketing-file requirements.	Requires disciplined chamber equilibration and background characterization — session time scales with the number of fan speeds and surrogate types tested.	ANSI/AHAM AC-1ISO 29462
ASHRAE-style room decay method (fit for purpose)	Flexible for larger devices or non-standard geometries beyond ANSI/AHAM AC-1 sizing — ASHRAE 52.2 framing supports commercial air-cleaner programs. Documents removal rate under ASHRAE 52.2 framing for indoor air quality assessments and occupant-exposure documentation.	Requires careful definition of mixing assumptions — without the AHAM chamber specification, comparability to AC-1-rated products must be stated in reporting.	ASHRAE 52.2
CADR plus filtration diagnostics bundle (fit for purpose)	Connects CADR to filter media efficiency and seal performance — ISO 29462 framing supports integrated product analysis across fan speeds. Single campaign delivers CADR by speed with pressure-drop and fractional efficiency data for design trade-off decisions and technical documentation.	More measurement surfaces than a standalone CADR campaign — adds media sample management and engineering setup time to the overall study scope.	ISO 29462
Loading and aging sensitivity study (fit for purpose)	Documents CADR drift with filter service life — removal rate versus load drives replacement interval decisions and end-of-life performance claims. Sequential CADR measurements across loading stages confirm whether performance stays within acceptable bounds under the same chamber decay methodology as baseline testing.	Longer total run time than a static CADR campaign — scales with the number of loading stages and required replicates per condition.	—

Setup configurations

Each CADR study uses a configuration matched to the device size, target standard, and surrogate aerosol set. The setup combines controlled background conditions, including defined chamber volume, stable mixing, and repeatable device placement, with the device's practical operating profile. The following variables are defined during study planning:

Device interfaces

Chamber volume selection, device placement, orientation, and fan-speed setpoints standardized across replicates — inlet and outlet orientation documented to avoid direct jet sampling bias.

Flow & actuation profiles

Defined fan speed settings and stabilization periods per condition — auto-mode and boost-mode characterization added when specific operating modes are part of the performance claim.

Environmental controls

Background decay characterization (device off) before each device-on sequence — temperature and relative humidity characterized and logged throughout to bound environmental uncertainty contributors.

Sample numbers

Replicates per fan speed and surrogate type, with repeated sequences for precision — replicate plan sized to expected variability in decay constants and the decision threshold for the claim.

Media & handling

Surrogate aerosol lot tracking and documented generation settings per run — smoke, dust, and allergen surrogates selected to match the target standard and product claim strategy.

Methods anchored to the standards that matter

Each CADR study operates within a documented quality system aligned with the chamber decay and air-cleaning standards used to characterize portable and whole-room devices. The four anchors below define the data requirements carried through to the Section 7 outputs.

ISO 17025AccreditedTesting-laboratory competence — documented methods, calibration traceability, and uncertainty contributors.
ANSI/AHAM AC-1AlignedChamber decay CADR method for portable air cleaners — smoke, dust, and pollen surrogate protocols.
ASHRAE 52.2AlignedParticulate efficiency framing for air-cleaning devices — MERV-rated performance context.
ISO 29462AlignedInternational field and laboratory measurement of air-cleaner performance and removal efficiency.

Key data outputs & reporting

Each CADR study provides removal rates by speed setting, fitted decay curves, and the associated replicate statistics. Primary metrics, QA/QC controls, and uncertainty contributors are formatted for product files, marketing claims support, or comparative performance documentation. The deliverables below are included in the standard report. Extended studies comparing device revisions, filter lots, or loading stages include additional comparison materials.

Primary outputs

CADR by fan speed setting for each surrogate aerosol (smoke, dust, allergen) in m³/min, with mean, SD, and CV across replicates.
Decay curves (device on and device off) with fitted removal constants — background decay correction applied and documented per run.
Uncertainty contributors including particle monitor response, chamber mixing assumptions, surrogate generation variability, and background decay correction.
Condition comparisons with summary statistics across fan speeds, surrogate types, and device configurations tested.

Deliverables

#	Format	Contents
01	PDF report	Methods, controls, decay curves, CADR summary, replicate statistics, and uncertainty contributors.
02	CSV / XLSX datasets	Time-series concentration, per-condition decay constants, and CADR summary by speed and surrogate.
03	Figures	Decay curve overlays, CADR bar summaries by speed and surrogate, and background correction documentation.

Extended deliverables · multi-arm comparability · stability · predicate studies

Multi-device comparison pack — Side-by-side CADR overlays and statistical framing for multiple devices, prototypes, or filter revisions.
Loading and aging summary — CADR versus load stage with performance envelope for filter replacement interval decisions.

QA / QC & data integrity

Each CADR study includes a documented QA/QC framework matched to the chamber setup, surrogate selection, and tested speed settings. Verifications are completed before and after each test set and audited within our ISO 17025 quality system. Calibration records remain traceable from particle counter characterization through the final decay constant and CADR result. Background checks and blank runs are standard for every campaign.

Pre- and post-run particle counter verification and calibration logs — confirms instrument sensitivity and background are within acceptance before each surrogate introduction and device-on sequence.

Chamber background runs (device off) and blank runs before each device-on phase — establishes ambient baseline and documents natural decay rate for background correction calculations.

Surrogate aerosol lot tracking and documented generation settings per run — aerosol starting concentration confirmed within acceptance window before timing the device-on decay sequence.

Replicate runs per fan speed and surrogate type with acceptance criteria on decay-curve fit quality and mixing stability — reproducibility confirmed before condition results are finalized.

Chain of custody and configuration documentation — device serial number, fan speed settings, chamber orientation photos, and inlet placement recorded per campaign for traceability.

Why ARE Labs

ARE Labs connects technical topics to practical study design, method selection, controlled aerosol work, and reportable evidence without turning technical pages into sales pages.

Reviewed byJamie Balarashti (25 yrs - cascade & inhalation methods) - Weston Schaper (7 yrs - real-time sizing & nanoparticle work)

17025Accredited testing

900+Studies Performed

17+Years in operation

300+Clients supported

Common questions

Quick answers to the questions air purifier developers, filter suppliers, and product managers ask when scoping a CADR study — surrogate selection, fan speed coverage, chamber sizing, background correction, and deliverables. The answers below are starting points; reach out if your device geometry, operating modes, or claim strategy doesn't match what's shown here, since most CADR studies involve at least one configuration choice customized to the device and regulatory frame.

Q.What is CADR and why does it matter for air purifier products?

A.CADR is the effective volumetric clean-air delivery rate a device provides for particles under a defined chamber decay method. Consumers and retailers use it as the primary performance metric for comparing air purifiers. Under ANSI/AHAM AC-1, the standard claim basis is speed-specific CADR for each surrogate type.

Q.Do I need to test all three surrogates — smoke, dust, and allergen?

A.Not always. Surrogate selection depends on the target standard, claim strategy, and intended product use. ANSI/AHAM AC-1 specifies all three surrogates for a full rating, while a narrower program may focus on the surrogate most relevant to the product's intended use environment.

Q.Can you test CADR at multiple fan speeds in one study?

A.Yes. Speed-specific CADR is a core study output and the primary decision variable for most programs. Each speed setting is evaluated with its own background-corrected decay sequence and replicate set. Both worst-case and best-case settings are documented.

Q.How do you account for natural particle decay in the chamber?

A.Before each device-on phase, we characterize background decay with the device off. We then subtract the natural decay rate when calculating the device's removal contribution. This correction accounts for ambient particle loss and is required under ANSI/AHAM AC-1.

Q.Can CADR testing be paired with filter media efficiency data?

A.Yes. We can combine CADR testing with filtration diagnostics in a single campaign. The study pairs device-level CADR at each speed setting with filter fractional efficiency and pressure-drop data, connecting media performance with whole-device air cleaning for design and qualification programs.

Q.What do I receive at the end of a CADR study?

A.Deliverables include a PDF report describing the methods, background correction, decay curves, and CADR summaries; CSV/XLSX datasets containing time-series concentrations and per-condition statistics; and decay-curve and CADR bar-chart figures for technical files or marketing documentation.

Standards & guidance

ARE Labs conducts CADR studies in alignment with the chamber decay and air-cleaning standards used to characterize portable and whole-room device performance. Methods covered by third-party accreditation are identified as accredited under ISO 17025. When a standard is followed but the method is not formally accredited, the method is described as aligned or conformant, where applicable. The cards below identify the standards most relevant to CADR testing programs.

QA & Regulatory - Accredited

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