This document applies to the basic safety and essential performance of a ventilator in combination with its accessories, hereafter referred to as ME equipment:  intended for use in an environment that provides specialized care for patients whose conditions can be life-threatening and who can require comprehensive care and constant monitoring in a professional healthcare facility; NOTE 1 For the purposes of this document, such an environment is referred to as a critical care environment. Ventilators for this environment are considered life-sustaining. NOTE 2 For the purposes of this document, such a ventilator can provide transport within a professional healthcare facility (i.e. be a transit-operable ventilator). NOTE 3 A critical care ventilator intended for use in transport within a professional healthcare facility is not considered as an emergency medical services environment ventilator.  intended to be operated by a healthcare professional operator; and  intended for those patients who need differing levels of support from artificial ventilation including for ventilator-dependent patients. A critical care ventilator is not considered to utilize a physiologic closed-loop-control system unless it uses a physiological patient variable to adjust the ventilation therapy settings. This document is also applicable to those accessories intended by their manufacturer to be connected to a ventilator breathing system, or to a ventilator, where the characteristics of those accessories can affect the basic safety or essential performance of the ventilator. NOTE 4 If a clause or subclause is specifically intended to be applicable to ME equipment only, or to ME systems only, the title and content of that clause or subclause will say so. If that is not the case, the clause or subclause applies both to ME equipment and to ME systems, as relevant. Hazards inherent in the intended physiological function of ME equipment or ME systems within the scope of this document are not covered by specific requirements in this document except in IEC 60601-1:2005, 7.2.13 and 8.4.1. NOTE 5 Additional information can be found in IEC 60601-1:2005+AMD1:2012, 4.2. This document is not applicable to ME equipment or an ME system operating in a ventilator-operational mode solely intended for patients who are not dependent on artificial ventilation. NOTE 6 A critical care ventilator, when operating in such a ventilator-operational mode, is not considered life-sustaining. This document is not applicable to ME equipment that is intended solely to augment the ventilation of spontaneously breathing patients within a professional healthcare facility. This document does not specify the requirements for:  ventilators or accessories intended for anaesthetic applications, which are given in ISO 80601-2-13[2];  ventilators or accessories intended for the emergency medical services environment, which are given in ISO 80601-2-84[3], the future replacement for ISO 10651-3[4];  ventilators or accessories intended for ventilator-dependent patients in the home healthcare environment, which are given in ISO 80601 2-72:2015[5];  ventilators or accessories intended for home-care ventilatory support devices, which are given in ISO 80601-2-79:2018[6] and ISO 80601-2-80:2018[7] ;  obstructive sleep apnoea therapy ME equipment, which are given in ISO 80601 2 70[9];  continuous positive airway pressure (CPAP) ME equipment;  high-frequency jet ventilators (HFJVs) and high-frequency oscillatory ventilators (HFOVs), which are given in ISO 80601 2 87[63]; NOTE 7 A critical care ventilator can incorporate high-frequency jet or high-frequency oscillatory ventilator-operational modes.  oxygen therapy constant flow ME equipment; and  cuirass or “iron-lung” ventilation equipment. 201.1.2 Object Replacement: The object of this document is to establish basic safety and essential performance requirements for a ventilator and its accessories. Accessories are included because the combination of the ventilator and the accessories needs to be adequately safe. Accessories can have a significant impact on the basic safety or essential performance of a ventilator. NOTE 1 This document has been prepared to address the relevant essential principles of safety and performance of ISO 16142-1:2016 as indicated in Annex CC. NOTE 2 This document has been prepared to address the relevant general safety and performance requirements of European regulation (EU) 2017/745 as indicated in Annex DD.