Abstract: This employer used a lyophilization process to produce a polymer wound dressing product. This product is then placed inside a freeze dryer for 26 hour and then the doors are open for 30 minutes before removing the product. The product is then removed from the trays and placed inside a box, then packaged for delivery to another company to perform cold sterilization. The area where employees remove product from the trays is under positive pressure by HEPA, filtering 6 microns and larger, supply and return air with 22 air changes per hour. The unloading room dimensions are 19-ft 11-in. long, 10-ft 2-in. wide, and 16-ft high. Employee PPE consisted of full body suit, nitrile gloves, foot covers and hair net. On March 23, 2007, after two hours of emptying trays, the employees were asymptomatic and return to their residence between 10:00 p.m. and 11:00 p.m. After a couple hours the employees were having difficulty breathing and eye discomfort and sought medical attention at the hospital. The medical staff admitted three employees between 1:00 a.m. and 12:00 p.m. on March 24, 2007, a period of 11 hours. The nature of the injuries suggested that an airborne compound or particulate was responsible for the observed effects. Detailed chemical and physical analysis of the dressing raw material components as well as final products indicate that the most likely causative agent is ammonia or a related amine-containing compounds cable of irritating mucosal tissue. Particulate composed of other dressing components, such as EDC, 1-(3-dimethylaminoproply)-3ethylcarbodimidehydrochloride or its urea derivative can not be ruled out. Ammonia and aliphatic amines may have originated from the protein or EDC raw materials, either as original impurities or through degradation due to manufacturing process conditions and or inappropriate storage protocols. Three employees were hospitalized.