Biological evaluation of breathing gas pathways in accordance with ISO 18562

The ISO 18562 standard series is used to evaluate the biocompatibility of medical devices with a breathing-gas pathway, particularly with respect to potentially hazardous substances the patient may be exposed to through the gas stream.

All parts of ISO 18562 were updated in 2024, introducing several new testing requirements for manufacturers of CPAP and anesthesia machines, ventilators, humidifiers, hyperbaric chambers, and other medical devices with a respirable gas stream. Some of the key changes include an extended range of volatile organic substances to be analyzed and a requirement to determine the volume of condensate that can reach the patient via the device.

After July 5th, 2026, all new premarket submissions to the FDA will have to refer to the revised versions of ISO 18562 standards.¹ Similarly, the 2024 editions are now recognized in the EU as harmonized standards, which means that testing new devices in accordance with them is the most straightforward way to demonstrate compliance with relevant parts of the EU MDR.²

This article summarizes all four parts of the updated ISO 18562 standard series, with a focus on testing-related practical implications to medical device manufacturers.

ISO 18562-1: Evaluation and testing within a risk management process

ISO 18562-1:2024 is similar to ISO 10993-1:2025 in that it outlines the general principles for biocompatibility testing and risk assessment. However, it does so specifically for gas pathways, as they are not sufficiently covered by the ISO 10993 series. 

The extent of biological evaluation required under ISO 18562-1 depends on the categorization of the gas pathway, the associated risks, and the degree to which these risks are addressed by existing data. The process typically proceeds in the following order: 

• Identification of biocompatibility hazards related to material composition, physical configuration, and performance characteristics of the device. 

• Evaluation of risks posed to the patient by these hazards, based on the intended total exposure duration and patient group.

• Creation of a biological evaluation plan (BEP), where the identified hazards and risks are documented, along with existing supporting evidence (e.g., scientific literature or prior test data).

• Identification of gaps not sufficiently addressed by existing data, and selection of tests to address these gaps.

• Testing in accordance with Part 2, Part 3, and/or Part 4 of ISO 18562, and other relevant standards, as required by the BEP.

• Preparation of a biological evaluation report (BER), summarizing the test results and the outcome of the final risk assessment.

In addition to exposure duration, the patient group influences tolerable exposure (TE) to hazardous substances. The newest version of ISO 18562-1 contains six patient groups: adult, adolescent, child, small child, infant, and premature neonate, each with its own daily breathing volume that is used to calculate maximum TE-levels for volatile organic substances and leachables.

ISO 18562-2: Tests for emissions of particulate matter

ISO 18562-2 specifies the tests and acceptance criteria for assessing patient exposure to particulate matter through the gas pathway of a medical device. To comply with the standard, breathing gas pathways must not expose the patient to levels of particulate matter in excess of the following limits:

• 12 µg/m³ for particles ≤ 2.5 µm in diameter (PM2.5)

• 150 μg/m³ for particles ≤ 10 µm in diameter (PM10)

The standard outlines several alternative test methods for measuring particulate matter emissions: 

• Single- and double-filter setups: A gas stream is directed through the medical device, and a particle filter is placed at the exit stream to trap all particles > 0.25 µm in diameter. Since particle sizes are not differentiated beyond this, the compliance limit is 12 µg/m³ for all trapped particles. 

  • If sufficiently clean air is not available for the single-filter test, another filter can be placed at the input stream. The difference in particulate matter concentrations at the different filters is then calculated to obtain the amount of particles added by the medical device. 

• Filter method with particle size-based separation: In addition to filters, the test setup includes an inertial particle size separator that separates particles into sub-10-µm and sub-2.5-µm fractions, so that concentrations can be compared to the size-dependent limits listed above.³

• Particle counter method: Particle counts by size range are measured in the exit stream using a calibrated particle counter. The results are then converted into mass concentrations and contrasted with the compliance limits.

ISO 18562-3: Tests for emissions of volatile organic substances

ISO 18562-3 specifies tests for the emissions of volatile organic substances (VOS) that may be inhaled by the patient while using the gas pathway device. The previous edition referred to volatile organic compounds (VOCs), but the terminology was updated for the 2024 version to include semi-volatile and very volatile organic compounds (SVOCs and VVOCs) in addition to VOCs. 

In the ISO 18562-3 test, the medical device is set up in a test chamber, kept at the highest foreseeable use temperature, and operated at the lowest clinically relevant flow rate, as these conditions lead to the worst-case inhalation dose. Air that has passed through the device is sampled and analyzed using a GC-MS method to identify and measure the concentrations of VOS in µg/m³. 

The results for each substance are then evaluated against maximum acceptable exposure limits, which are derived from toxicological data and the standard daily breathing volumes specified for different patient groups in ISO 18562-1. The worst-case intended patient group (i.e., the one resulting in the lowest allowable concentration) is used for the calculations.

ISO 18562-4: Tests for leachables in condensate

ISO 18562-4 outlines tests to evaluate substances that could dissolve into condensate inside the breathing gas pathway and reach the patient through it. The procedure is the following:

• The first step is to determine the volume of liquid condensate that can reach the patient in 24 hours when the device is operated under worst-case clinically relevant parameters. If it can be shown that no more than 0.1 ml of condensate can reach the patient in 24 hours, further testing is not needed.

• If the condensate volume is larger, the next step is to identify and quantify leachables in the condensate using several analytical methods (GC-MS and LC-MS for organic leachables, and ICP-MS for inorganic elements) in accordance with ISO 10993-18.

• Measured leachable concentrations are contrasted with substance-specific tolerable intake limits, which are calculated based on ISO 18562-1 for organic leachables, and the ICH Q3D guideline for inorganic leachables. 

• If the tolerable intake is exceeded for any substance, a toxicological risk assessment according to ISO 10993-17 is required. 

Our solutions for breathing gas pathway testing

Measurlabs offers the full range of analyses required for the biocompatibility evaluation of breathing gas pathways in accordance with ISO 18562. If the device contains parts that come into direct contact with the patient, the testing program can be extended to include the relevant ISO 10993 tests. 

We recommend starting the process by creating a biological evaluation plan (BEP), as this will outline the required tests for the specific device. If you do not yet have the BEP, we can help prepare it. Please contact our experts using the form below to discuss your testing needs and to receive a custom quote.