Heat and moisture exchangers (HMEs) are used to warm and humidify the gas delivered to patients during anaesthesia and in intensive care. Typically, HMEs are connected between the tracheal tube or catheter mount and the breathing system. This point of connection has been identified as having a high risk of disconnection. To reduce the possibility of disconnection, the International Standard for HMEs specifies that the connectors on an HME shall comply with ISO 5356-1: 1987, the International Standard for cones and sockets. A simple method is described to test whether or not the connectors comply with this standard. This method is used when evaluating HMEs for the Medical Devices Agency (MDA). Results are quoted from the MDA series Evaluation. The majority of connectors tested were found to comply with the standard. The test method is also suitable for testing conical connectors on other devices.