Standards Development

Scope

This document specifies the properties, designation, generation principle, particle size distribution, concentration stability, chemical composition, and verification of a laboratory-generated salt aerosol intended to reproduce the sub-micrometre accumulation-mode fraction of typical urban atmospheres. This document is intended for use in laboratory evaluation, ageing, conditioning, or loading of air filters and air-cleaning equipment, including general ventilation filters evaluated in conjunction with the ISO 16890 series.

This document does not specify a complete ageing procedure, a filter loading endpoint, an efficiency test method, an energy-use calculation, a filter classification method, a life-cycle cost method, or a calibration aerosol for particle counters. It does not replace coarse-test dust standards when a coarsedust challenge is required.

Purpose

This document specifies the characteristics of a fine synthetic aerosol mainly intended for the laboratory ageing of air filters for general ventilation. It defines the aerosol’s generation principle (thermal vaporization and condensation of an inorganic salt, e.g., KCl), with a particle size distribution representative of the urban accumulation mode.

The document contains stability criteria, permissible concentration ranges for accelerated conditioning, and relevant metrological properties. It does not prescribe an ageing procedure; such procedures could be part of a separate standard. The aerosol specified here is designed to be compatible with efficiency classifications determined in ISO 16890-1 (ePM1 and ePM2.5).

Justification - The existing ISO 15957 relies on coarse synthetic dusts that predominantly cause surface cake formation and were intended for comparative product testing. In practice, results obtained with these coarse dusts are often inappropriately used to infer in-service behaviour, including energy use, which has created confusion among designers and users. In real urban outdoor environments — where supply-air filters most strongly affect indoor air quality — the loading aerosol is dominated by sub-micrometre particles in the accumulation mode (as defined in ISO 16890-1).

For filters classified as ePM1 and ePM2.5, this fine fraction drives depth filtration and leads to loading kinetics and service life that differ markedly from those observed when clogging the air filters with coarse test dusts. Consequently, current practice is inadequate for predicting pressure-drop development, energy impact, and change-out intervals, and it does not support robust economic or environmental assessments.

The absence of a standardized fine aerosol for air filter ageing also hampers technological progress. Manufacturers of advanced media that can maintain required efficiency with lower airflow resistance over their service life cannot credibly demonstrate those benefits when testing is constrained to an artificial coarse aerosol. As a result, products tend to be optimized for the test, not for real-world conditions, limiting achievable reductions in filtration energy use.

Specifying a fine synthetic aerosol that reproduces the sub-micrometre urban mode, while allowing accelerated conditioning at controlled high concentrations, will:

 • yield pressure-drop-versus-deposited-mass trends that are more representative of service conditions;

• improve the consistency between ageing parameters and efficiency assessment in the ISO 16890 series;

 • enable fair, reproducible comparisons of innovative filter materials;

 • support more reliable predictions of energy impact, change-out intervals, and life-cycle cost and environmental performance.

By aligning the conditioning challenge with real atmospheric particle size distributions, this document removes a key methodological barrier and facilitates measurable advances in filter energy efficiency and overall performance.