Aspergillus spp.are thermotolerant fungi that cause significant disease among immunocompromised hosts, primarily pneumonia and sinusitis that will disseminate to other organs including the skin and the brain (see the definition).  These fungi are ubiquitous, found in soil, water and decaying material and cause infections by inhalation of contaminated aerosols.  The most common species causing infection include Aspergillus flavus, Aspergillus terreus, and Aspergillus fumigatus.  The attributable mortality of pneumonia caused by Aspergillus species was 85%.  Up to 12.5% of at risk patients may develop infections.  However, the incidence of this disease is clearly dependent upon a number of factors including the type of and amount of immunosuppression, conditioning process used during transplantation, the severity of GVHD that develops, the institution’s air filtration and the environment, the season and other undefined or competing factors.  The data supporting aspergillus as an environmental pathogen include that infection starts in sinuses or lungs. Outbreaks are associated with unfiltered air, contaminated ventilation systems at intake and exhaust ducts, and dust that is dislodged by renovation and construction.  Finally, hospitals that have improved ventilation systems have decreased case rates 10 fold. How well do HEPA's work? In addition, control of this organism requires environmental monitoring and engineering manipulations. Air sampling is indicated if cases are identified while a source is investigated, with on going construction and prior to opening units to high-risk patients.  Air should be sampled using a high volume air sampler.  Construction standards are required on any unit housing transplant or immunocompromised patients.  These include many elements including placing appropriate barriers, moving high risk patients, using HEPA filtration and exhausting construction dust appropriately. Many surfaces, such as fireproofing can harbor organisms including aspergillus.  Hence agents such as copper-8-quinonolate, a fungicide is used to decontaminate environmental surfaces. (See JHH Control Plan and General Recommendations) After construction, one must assure the new filters are properly seated.  When damage, such as water, fire to a unit occurs, infection control personnel need to inspect the area and consider air and environmental sampling.