Purification Efficiency Testing: Standards, Methods, and Technical Requirements

Purification efficiency testing is a laboratory verification process that quantifies how effectively air purifiers, kitchen fume purification equipment, industrial waste gas treatment systems, air filters, and water purification products remove targeted contaminants from air, gas, or water streams. This technical article explains the key testing parameters, applicable standards such as GB/T 18801, EN ISO 29463, ISO 16890, and GB/T 5750, sample requirements, testing methodologies, and efficiency calculation principles used by accredited third-party laboratories. It serves as a practical reference for manufacturers, engineers, and procurement professionals who need reliable performance data for certification, compliance, and product development.

Technical Overview

Purification efficiency is the primary quantitative indicator of a purification device's performance. It expresses, as a percentage, the ratio of a specific pollutant removed by the device to the amount of that pollutant present before treatment, measured under controlled laboratory conditions. Because regulatory compliance, product certification, procurement decisions, and marketing claims all rely on this figure, independent testing by accredited third-party laboratories is essential for credibility and market acceptance.

The scope of purification efficiency testing spans a wide range of technologies: physical filtration (HEPA and ULPA media), electrostatic precipitation, activated carbon adsorption, photocatalytic oxidation, ultraviolet sterilization, plasma ionization, wet scrubbing, and membrane-based water treatment. Each technology is evaluated against the pollutants it is designed to target, including particulate matter such as PM2.5 and PM10, gaseous compounds such as formaldehyde and volatile organic compounds (VOCs), microorganisms, oil fume droplets, and waterborne contaminants such as heavy metals and residual chlorine.

Core metrics derived during testing include single-pass removal efficiency, clean air delivery rate (CADR), cumulative clean mass (CCM), pressure drop, ozone emission, and microbial kill rate. These metrics are defined by internationally recognized standards published by ISO, IEC, EN, ASTM, UL, JIS, and GB (Chinese national standards), which specify test rigs, environmental conditions, pollutant generation methods, and data processing rules to ensure reproducible and comparable results between laboratories.

Testing Samples

Household and Commercial Air Purifiers

Freestanding portable air cleaners used in residential, office, and medical environments. These units are evaluated for particulate CADR, gaseous pollutant CADR (formaldehyde, toluene, and total VOCs), CCM, and ozone emission, primarily in accordance with GB/T 18801-2015 and related international test procedures.

Kitchen Oil Fume Purification Equipment

Electrostatic, mechanical filtration, and wet-type oil fume purifiers installed in commercial kitchen exhaust systems. Testing verifies oil droplet removal efficiency and outlet emission concentration against the limits established in GB 18483.

Industrial Waste Gas Treatment Equipment

Scrubbers, activated carbon adsorption units, regenerative thermal and catalytic oxidizers, baghouse dust collectors, and deNOx systems. Efficiency testing covers particulate, acid gas, VOC, and nitrogen oxide removal to demonstrate compliance with emission permits and environmental regulations.

Air Filters and Filter Media

Panel filters, bag filters, compact filters, HEPA and ULPA filters, and roll media evaluated for fractional efficiency, minimum efficiency reporting value, most penetrating particle size (MPPS) efficiency, and leak integrity in accordance with EN 1822, EN ISO 29463, ISO 16890, GB/T 14295, GB/T 13554, and JIS B 9908.

Water Purification Products

Household reverse osmosis units, ultrafiltration systems, ceramic filters, and replacement cartridges. Testing measures rejection or removal rates for turbidity, residual chlorine, heavy metals such as lead and arsenic, organic matter, and total dissolved solids, with analytical methods following GB/T 5750 and hygiene safety limits aligned with GB 5749.

Testing Items

Typical test parameters requested by manufacturers and end users include:

• Particulate purification efficiency for PM2.5, PM10, cigarette smoke, and standardized test dust
• Gaseous pollutant removal efficiency for formaldehyde, toluene, benzene, ammonia, total VOCs, sulfur dioxide, nitrogen oxides, and hydrogen sulfide
• Oil fume purification efficiency and outlet emission concentration for commercial kitchen exhaust devices
• Microbial removal rate and antibacterial (kill) rate against Staphylococcus aureus, Escherichia coli, Candida albicans, and natural airborne bacteria
• Clean air delivery rate (CADR) and cumulative clean mass (CCM) for air purifiers
• Single-pass filtration efficiency and pressure drop for filter elements and media
• Ozone emission and secondary by-product generation, including ozone-free validation under UL 2998
• Water purification efficiency for turbidity, residual chlorine, heavy metals, chemical oxygen demand, and total dissolved solids rejection

Testing Methods

Environmental Test Chamber Method

The device under test operates inside a sealed environmental chamber, typically 30 cubic meters for full-size air purifiers per GB/T 18801-2015, or smaller 1 to 3 cubic meter chambers for material and component screening. A known concentration of the target pollutant is generated, and its decay over time is recorded. Natural decay is measured in a blank run and subtracted, and CADR is calculated as the product of chamber volume and the difference between total decay and natural decay constants. This method also supports formaldehyde, toluene, and mixed VOC challenge tests.

Upstream and Downstream Duct Method

Filter elements are installed in a standardized test duct. A challenge aerosol is generated upstream, and particle counters or optical photometers measure concentrations simultaneously upstream and downstream. Single-pass efficiency is calculated as the upstream concentration minus the downstream concentration, divided by the upstream concentration, multiplied by 100 percent. For HEPA and ULPA filters, EN 1822 and EN ISO 29463 define the MPPS scan procedure, while ISO 16890 applies to general ventilation filters using ISO A1 through ISO A15 ePM classes. Sodium chloride flame methods and PAO photometer scanning are used for leakage detection and integrity verification.

Gravimetric and Concentration Comparison Method

For dust collectors and oil fume purifiers, isokinetic sampling is performed at the inlet and outlet of the equipment under rated airflow. Trapped particulate or oil mass is determined gravimetrically or by infrared photometric analysis of extractable oil. Removal efficiency equals the inlet mass minus the outlet mass, divided by the inlet mass, multiplied by 100 percent. Gaseous treatment equipment is evaluated by comparing inlet and outlet concentrations measured with instrumental or wet-chemical methods.

Microbiological Challenge Method

A nebulized bacterial suspension is introduced into the test chamber or airflow, and viable colony-forming units are counted before and after the purification process. The kill or removal rate equals the initial count minus the final count, divided by the initial count, multiplied by 100 percent. Ultraviolet devices are additionally validated for irradiation dose, and photocatalytic materials are tested under controlled illumination and humidity conditions.

Water Purification Performance Method

Influent and effluent samples are collected at defined flow rates and recovery ratios across multiple operating cycles. Contaminant concentrations are determined using standard analytical procedures, and removal efficiency equals the influent concentration minus the effluent concentration, divided by the influent concentration, multiplied by 100 percent. Structural integrity and material safety are assessed in parallel where required.

Applications

Purification efficiency testing results are used across the full product lifecycle:

• Product certification and market access, including voluntary performance labeling and support for CE declarations under EN and IEC standards
• Verification of advertising and performance claims for retail and e-commerce channels
• Green building assessment programs, cleanroom classification, and indoor air quality engineering
• Emission compliance demonstration for industrial facilities and commercial kitchens
• Research and development benchmarking, filter media selection, and production quality control
• Tender documentation, government procurement, and third-party performance audits
• Occupational health investigations and post-installation acceptance testing

FAQ

How is purification efficiency calculated?

The general formula is efficiency equals the concentration before purification minus the concentration after purification, divided by the concentration before purification, multiplied by 100 percent. For flow-through equipment, concentrations are measured simultaneously upstream and downstream; for chamber tests, initial and final concentrations are compared with natural decay correction applied.

What is the difference between purification efficiency and CADR?

Efficiency is a percentage describing contaminant removal per pass or over a defined interval, while CADR expresses the volume of clean air delivered per unit of time by combining efficiency with airflow. CADR better reflects whole-room performance, which is why standards such as GB/T 18801-2015 report both metrics.

Which standards govern purification efficiency testing?

Commonly applied standards include GB/T 18801-2015 for air purifiers, EN 1822 and EN ISO 29463 for HEPA and ULPA filters, ISO 16890 for general ventilation filters, GB/T 14295 and GB/T 13554 for Chinese filter classifications, GB 18483 for kitchen fume emissions, the ISO 16000 series for indoor air measurement, UL 867 and UL 2998 for electrostatic cleaners and ozone-free validation, JIS B 9908 for filter elements, and GB/T 5750 for drinking water analysis methods.

What samples and quantities should be submitted for testing?

Laboratories generally require one to three complete production units together with spare filters or consumables, plus technical documentation such as rated airflow, power rating, and operating modes. For filter media and material studies, sample sheets of specified dimensions are sufficient. Exact requirements should be confirmed with the accredited laboratory before submission.

How long does purification efficiency testing take?

Standard chamber or duct efficiency tests typically complete within five to fifteen working days. Microbiological tests require additional incubation periods, and CCM or service life verification may extend over several weeks because repeated challenge cycles are necessary to reach filter saturation.

Are test reports from accredited laboratories accepted for compliance purposes?

Yes. Reports issued by accredited third-party laboratories operating under internationally recognized accreditation frameworks are widely accepted for regulatory filings, tender submissions, certification schemes, and contractual acceptance, provided the test methods and standards cited match the requirements of the target market.