ISO 23328-1:2003

Overview

ISO 23328-1:2003 specifies a short-term salt test method to assess the filtration performance of breathing system filters (BSF) used in anaesthetic and respiratory clinical breathing systems. The standard defines a laboratory procedure that challenges BSF with a controlled sodium chloride aerosol and measures particle penetration to quantify filtration efficiency. It is intended for comparison testing of BSF intended to filter respired gases and is not applicable to filters for vacuum sources, gas sampling lines, compressed gases, or physiological test equipment.

Key Topics and Requirements

• Test principle: Nebulize a sodium chloride solution into an airstream; neutralize particle charge to the Boltzmann equilibrium; measure upstream (challenge) and downstream (penetration) concentrations.
• Particle challenge: Most penetrating particle size range targeted (~0.1–0.3 µm). Aerosol particle distribution calibration uses a count median diameter of 0.075 µm with GSD ≤ 1.86 (MMAD ≈ 0.26 µm).
• Environmental conditions: Temperature (23 ± 2) °C, relative humidity (60 ± 15) % RH, pressure (96 ± 10) kPa.
• Flowrates: Test flows represent clinical use - Adult: 30 L/min, Paediatric: 15 L/min.
• Apparatus & instruments: Accurate flowmeter (±5%), sodium chloride aerosol generator, scanning mobility particle sizer (or equivalent), and forward-light-scattering photometers for upstream/downstream concentration measurement.
• Conditioning (Annex A): BSF are conditioned by exposure to humidified air in a patient-model breathing system to simulate clinical use (e.g., 25 ± 1 h if manufacturer’s maximum not specified).
• Calculation: Penetration value (PV) = (cP / cC) × 100; percent filtration efficiency = 100 − PV.
• Reporting & sampling: Manufacturer documents sample size rationale; test report must identify BSF, lot/date, quantity tested, and efficiencies for unconditioned and conditioned states.
• Limitations: Test is for comparative performance only; phenomena such as channeling and grow-through are recognized but not quantified by this method.

Applications and Users

• Medical device manufacturers: for product development, quality control, and certification of breathing system filters.
• Independent testing laboratories: to perform standardized filtration performance assessments.
• Regulatory bodies and procurers: to evaluate claims and compare BSF performance for clinical use.
• Clinical engineers and infection control teams: to understand filter capabilities and limitations in respiratory and anaesthetic circuits.

Related Standards

• ISO 23328-2 - addresses non-filtration aspects of breathing system filters (design, safety, labelling).
• Annex D of ISO 23328-1 references ISO/TR 16142 for essential principles related to medical device evaluation.

Keywords: ISO 23328-1, breathing system filters, BSF, salt test method, sodium chloride aerosol test, filtration efficiency, particle size distribution, clinical breathing system.