This document specifies:

—？the general principles governing the biological evaluation within a risk management process of the 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 general categorization of gas pathways based on the nature and duration of their contact with the gas stream;

—？the evaluation of existing relevant data from all sources;

—？the identification of gaps in the available data set on the basis of a risk analysis;

—？the identification of additional data sets necessary to analyse the biological safety of the gas pathway;

—？the assessment of the biological safety of the gas pathway.

This document covers general principles regarding biocompatibility assessment of medical device materials, which make up the gas pathway, in normal use and normal condition. This document does not cover biological hazards arising from mechanical damage.

The other parts of ISO？18562 cover specific tests that address potentially hazardous substances that are added to the respirable gas stream and establish acceptance criteria for these substances.

This document addresses potential contamination of the gas stream arising from the gas pathways within the medical device, which might then be conducted to the patient.

This document applies over the expected lifetime of the medical device when operated according to the instructions for use. This includes degradation arising from exposure to environmental conditions as well as cleaning, disinfection and sterilisation (i.e. processing). It also includes user action or inaction (omission) that leads to an unintended or unexpected outcome (result) (i.e. use error). It does not include conscious/intentional action or inaction that violates the instructions for use and is beyond reasonable risk control by the manufacturer (i.e. abnormal use).

This document does not address biological evaluation of the surfaces of medical devices that have direct contact with the patient or user. 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 equipment, 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 system filters and Y-pieces as well as any breathing accessories intended to be used with such medical 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 is not addressed by ISO？18562 (all parts).