Abstract: On June 3, 2010, A crew of four or five employees would normally work during the evening hours to clean the interior of planes remaining overnight at the Dane County Regional Airport. The typical cleaning process would take approximately 90 minutes. The crew used a few different cleaning supplies to clean different areas of the plane, such as the lavatories, trash containers, floors and windows. Personal protective equipment used was limited to rubber gloves. Concentrated cleaning chemicals were diluted in 5 gallon containers and then dispensed into spray bottles for use. An automatic mixing system had been in place until sometime in 2005 when the process switched to manual mixing of the chemicals. There were no specific procedures or measurements for mixing. When a cleaning chemical was in short supply, an employee added more concentrated chemical and water. An investigation determined that employees routinely used more of the concentrated chemical than the manufacturer's instructions indicated. One particular employee had been working on the cleaning crew since December of 2007. This cleaning crew employee started feeling ill on approximately March 6, 2010. The employee had been using a cleaning chemical that was sprayed from a spray bottle while cleaning the lavatories of the planes. The cleaning chemical was 3M Brand Disinfectant Cleaner No. 5. The employee experienced symptoms including swelling and discoloration of the nose, cheeks and eyes and burning sensations on the face and in the nasal passage. The employee went to a physician for treatment multiple times following the exposure. The employee was placed on restricted duty to not work around the cleaning chemicals, but was still working in the planes where cleaning chemicals were used. The use of the concentrated cleaning chemical in the small enclosed area of the lavatory was determined to be the cause of the illness. The employee went on vacation on May 5, 2010, but returned on May 10, 2010 due to the illness. The employee was then hospitalized on May 12, 2010 with dry cough, shortness of breath, weight loss and hazy infiltrates in the lungs associated with the illness. The employee's condition gradually worsened and the employee passed away on June 3, 2010. The coroner determined the cause of death to be hypoxic respiratory failure due to the occupational chemical exposure. The employer discontinued the use of the cleaning chemical.