Background: The UK High-Consequence Infectious Diseases (HCID) Network of high-level isolation units provides care for patients with contact-or airborne-transmissible highly infectious and highly dangerous diseases. In most HCID units, the healthcare workers (HCWs) wear personal protective equipment (PPE) ensembles incorporating a powered air-purifying respirator (PAPR) for head and respiratory protection. Some PAPRs have com-ponents worn outside/over other PPE, necessitating decontamination of re-usable ele-ments. Two alternative PAPRs, with all re-usable elements worn under PPE, were trialled in this study.Aim: To undertake scenario-based testing of PAPRs and PPE to determine usability, comfort and ability to remove contaminated PPE without personal cross-contamination.Methods: Trained healthcare volunteers (N1/420) wearing PAPR/PPE ensembles were sprayed with ultraviolet fluorescent markers. They undertook exercises to mimic patient care, and subsequently, after doffing the contaminated PPE following an established protocol, any personal cross-contamination was visualized under ultraviolet light. Par-ticipants also completed a questionnaire to gauge how comfortable they found the PPE.Findings and conclusions: The ensembles were tested under extreme ''worst case sce-nario'' conditions, augmented by physical and manual dexterity tests. Participating vol-unteers considered the exercise to be beneficial in terms of training and PPE evaluation. Data obtained, including feedback from questionnaires and doffing buddy observations, supported evidence-based decisions on the PAPR/PPE ensemble to be adopted by the HCID Network. One cross-contamination event was recorded in the ensemble chosen; this could be attributed to doffing error, and could therefore be eliminated with further practice. 2023 Published by Elsevier Ltd on behalf of The Healthcare Infection Society.