ISO 29461-1:2021

Overview

ISO 29461-1:2021 - "Air intake filter systems for rotary machinery - Test methods - Part 1: Static filter elements" defines standardized laboratory methods to determine the static performance of particulate air filters used in air intake systems for rotary machinery (stationary gas turbines, compressors and other stationary internal combustion engines). It extends and applies test procedures from ISO 16890 and ISO 29463 to filter elements operating at typical turbo‑machinery flow rates (0.24 m3/s to 2.36 m3/s). The standard covers individual filter element testing, classification and reporting, but does not directly predict in‑service lifetime or efficiency by itself.

Key topics and technical requirements

• Scope and applicability: Static (barrier) filter elements; can be applied to other filter types for initial efficiency evaluation. Applicable to filters tested by ISO 16890 (lower efficiencies) and ISO 29463 (EPA/HEPA and ≥85% MPPS efficiency).
• Test rig and mounting: Uses a duct test assembly (typical square duct ~610 × 610 mm; filter section 616–622 mm) with minimum section length ≥1.1 × filter length (min. 1 m). Guidance for mounting cartridges, cylindrical and special geometries is provided.
• Efficiency classification: Filters are classified by group/class based on MPPS and ePM values; EPA and HEPA classes require ISO 29463 methods and leak testing where applicable.
• Loading and resistance tests: Procedures for determining airflow resistance versus captured dust mass follow ISO 16890-3. Loading dust L2 (ISO 15957) is used for reporting. Final resistance endpoints: typically 375 Pa for coarse filters (ePM < 50%) and 625 Pa for fine/EPA/HEPA groups (ePM ≥ 50%).
• Initial gravimetric arrestance: Measured as the retained mass after the first 100 g of dust (or 15 Pa increase, whichever first) and expressed as a percentage.
• Conditioning and electrostatic effects: Conditioning methods (ISO 16890-4 / ISO 29463-5) identify media whose efficiency depends on electrostatic charge and determine minimum fractional test efficiency.
• Reporting and limitations: Detailed reporting requirements and a clear note that laboratory performance cannot alone quantitatively predict in‑service lifetime or efficiency.

Applications and target users

• Filter manufacturers validating static filter elements for turbo‑machinery intake systems.
• Turbine and compressor OEMs specifying intake filtration performance.
• Test laboratories performing standardized efficiency, loading and leak tests.
• Procurement, specification and maintenance engineers assessing filter selection for harsh or variable environments (desert, marine, industrial).

Related standards

• ISO 16890 (all parts) - Air filters for general ventilation (fractional efficiencies, ePM).
• ISO 29463 (all parts) - High efficiency filters and media (MPPS, HEPA/ULPA testing).
• ISO 15957 - Test dusts for evaluating air cleaning equipment.
• ISO 29464 - Terminology for cleaning of air and other gases.

Keywords: ISO 29461-1:2021, air intake filter systems, rotary machinery, static filter elements, test methods, ISO 16890, ISO 29463, EPA, HEPA, airflow resistance, gravimetric arrestance.