Overview
EN ISO 23328-1:2008 (ISO 23328-1:2003) specifies a short-term airborne sodium chloride (salt) test method to assess the filtration performance of breathing system filters (BSF) used in anaesthetic and respiratory clinical breathing systems. Adopted by CEN, this standard defines how to challenge BSF with a controlled NaCl aerosol and measure particle penetration to produce comparable filtration-efficiency results. The method is intended for comparative testing and does not by itself establish clinical risk.
Key topics and technical requirements
- Scope: Applies to BSF intended for filtration of respired gases in clinical breathing systems. Not applicable to filters for vacuum sources, gas sample lines, compressed gases, or physiologic test equipment. Non-filtration aspects are covered in ISO 23328-2.
- Challenge aerosol: Nebulized sodium chloride producing particles in the most penetrating size range (approximately 0.1 µm to 0.3 µm).
- Test principle: Measure challenge concentration (mg·m‑3) entering the BSF and penetration concentration leaving the BSF; compute percent filtration efficiency.
- Test conditions: Ambient test environment specified as 23 ± 2 °C, 60 ± 15 % RH, and 96 ± 10 kPa.
- Apparatus and instruments: Flowmeter (±5 % accuracy), sodium chloride aerosol generator (producing 10–20 mg·m‑3 at ~25 ± 5 °C and 30 ± 10 % RH, neutralized to Boltzmann equilibrium), a scanning mobility particle sizer (or equivalent), and a forward-light-scattering photometer (or equivalent).
- Conditioning: BSF are tested both unused and after conditioning to simulate humid clinical use (see Annex A).
- Reporting: Test report must include method parameters, sample size rationale, environmental conditions, measured concentrations, and calculated penetration/efficiency.
Applications and practical value
- Product development and R&D for breathing system filters (BSF) - to compare filter media and designs under standardized conditions.
- Quality control and batch acceptance testing in manufacturing.
- Independent test laboratories validating manufacturer claims on filtration performance.
- Regulatory and conformity assessment support - the European adoption includes an Annex ZA mapping the standard to essential requirements of Directive 93/42/EEC (medical devices) for relevant compliance evidence.
- Procurement and clinical engineering teams can use test data to inform device selection for anaesthesia and respiratory care settings.
Who should use this standard
- Medical device manufacturers of breathing system filters
- Test laboratories and certification bodies
- Regulatory affairs professionals and quality managers
- Clinical engineers and hospital procurement specialists
- R&D teams evaluating filtration media and designs
Related standards
- EN ISO 23328-2 - Non-filtration aspects of breathing system filters (complementary document)
- ISO/TR 16142 - Referenced for essential principles mapping (see Annex D)
Keywords: breathing system filters, BSF, EN ISO 23328-1, salt test, sodium chloride aerosol, filtration performance, medical device testing, aerosol particle size.