Immunocompromised patients — Special interventions are warranted for patients undergoing hematopoietic cell transplantation to minimize exposure to invasive fungal infections such as aspergillosis. These include high-efficiency particulate air (HEPA) filtration of incoming air, positive room air pressure relative to corridors, directed room air flow, ventilation systems that provide at least 12 air changes per hour, dust control measures, and the prohibition of flowers and potted plants in patient rooms. (See "Overview of infections following hematopoietic cell transplantation".)