The HEV (hev.web.cern.ch) is a fully functional, very versatile ventilator, designed to provide long-term alveolar ventilation support to patients, both in and out of intensive care, for intubated and non-invasive cases. Its pneumatic design around a buffer, the related feedback control system and its software control make it ready to be adapted to different use scenarios. The HEV’s main advantages are its use of readily available low-cost components, its versatility, and its performance.