To investigate effectiveness, safety and ease of application of Cryo Collar to rapidly reduce core brain temperature, the study will recruit 8 healthy volunteers, 10 adult normothermic participants and 10 adult sick febrile participants from Neurocritical Care ICU in The Ohio State University Wexner Medical Center. Before placing the collar around participant's neck, the investigators will record the participant's ear temperature and heart rate as a baseline. An Excel Cryo Collar will be placed around the participant's neck. After activating the cooling element, the investigators will place it within the neck collar.