This document specifies tests for substances leached by liquid water condensing in gas pathways of a medical device, its parts or accessories, which are intended to provide respiratory care or supply substances via the respiratory tract to a patient in all environments. The chemical characterization methods described in this document apply to chemical substances that could leach from the medical device, its parts or accessories into the condensate. This document establishes verifiable acceptance criteria for these tests. The identity and quantity of each chemical released is intended for toxicological risk assessment as described in ISO 18562-1:2024. This document addresses potential contamination of the gas stream arising from the gas pathways, which deliver breathing gas to the patient. This document applies over the expected lifetime of the medical device in normal use and takes into account the effects of any intended processing. This document does not address biological evaluation of the surfaces of gas pathways that have direct contact with the patient. The requirements for direct contact surfaces are found in the ISO 10993 series. Medical devices, parts or accessories containing gas pathways that are addressed by this document include, but are not limited to, ventilators, anaesthesia workstations (including gas mixers), breathing systems, oxygen conserving devices, oxygen concentrators, nebulizers, low-pressure hose assemblies, humidifiers, heat and moisture exchangers, respiratory gas monitors, respiration monitors, masks, medical respiratory personal protective equipment, mouth pieces, resuscitators, breathing tubes, breathing systems filters, Y-pieces and any breathing accessories intended to be used with such devices. The enclosed chamber of an incubator, including the mattress, and the inner surface of an oxygen hood are considered to be gas pathways and are also addressed by this document. This document does not address contamination already present in the gas supplied from the gas sources while medical devices are in normal use. EXAMPLE Contamination arriving at the medical device from gas sources such as medical gas pipeline systems (including the non-return valves in the pipeline outlets), outlets of pressure regulators connected or integral to a medical gas cylinder, or room air taken into the medical device. This document does not address contact with drugs or anaesthetic agents. If a medical device or accessory is intended to be used with anaesthetic agents or drugs, then additional testing can be required. This document is intended to quantify hazardous water-soluble substances that are leached from the medical device, its parts or accessories by condensate and then conveyed by that liquid to the patient.