A new Canadian standard (CAN/CSA/Z264.1-02:2002) has been published with the purpose of helping to ensure the safety, efficacy and functionality of spacers and/or holding chambers. They are prescribed for use by spontaneously breathing patients for the treatment of various respiratory diseases where medication is delivered to the lungs using pressurized-metered dose inhalers. This consensus standard was developed with the support of pharmaceutical companies and manufacturers of spacers and holding chambers, and with the help of clinicians, retail pharmacists and representatives of patient advocate bodies associated with respiratory diseases and the dissemination of information related to the treatment and the delivery of inhaled medications. Advice was also sought from expert groups outside of Canada to ensure that the standard would be relevant internationally. Whereas monographs in the pharmaceutical compendia and guidance documents published by regulatory bodies provide information that is largely about the drug product and inhaler, this is the only standard whose focus is primarily on these add-on devices. The purpose of the present review is to highlight the main features of the standard for clinicians by describing its scope, the tests that are intended to assure the robustness of the construction of these devices, the type of testing that is specified to establish in vitro efficacy, and the recommendations for the marking and labelling of the device and its associated packaging. Manufacturers who test their products to this Canadian Standards Association standard will be able to provide performance information about add-on devices to the clinician, facilitating an informed decision when selecting devices for patients.