This part of EN 13544 specifies requirements for tubing to be used with equipment for the therapeutic administration of respirable gases in domiciliary, ambulance and hospital practice including the interface to the equipment i.e. nipples and screw threaded connectors. This tubing is mainly used with oxygen, air or mixtures of these gases. The interface specifications are given to ensure interchangeability of respiratory therapy equipment thereby enabling patients to receive continuous treatment in all these clinical situations. Weight-bearing screw-threaded connectors are specified for use at the outlet of e.g. flowmeters to which devices such as humidifiers or nebulizers can be attached.