An evacuation of BNC occurred on Saturday evening, 28 July 2007, due to a strong odor in the cleanroom and remainder of the building. It was determined that this odor was not caused by an event internal to the facility and that it provided no hazard to occupants. The building reopened, and has been in normal operation since early Sunday morning. The details of the incident follow: On Saturday evening, 28 July 2007, a graduate student in the cleanroom smelled an overpowering odor that was thought to be a gas release. Not knowing the nature of the gas, he made the very appropriate decision to exit the cleanroom and sound the evacuation alarm. In the absence of more information, this was the right decision to ensure the safety of all those present in the facility. The building was closed at that point, and doors were secured. On exiting the building, the smell was significantly stronger west of the building that it was inside the building. During the response to the emergency it was determined that the smell in the building was caused by one or more skunks (possibly two skunks fighting) upwind of the building. The odors from the release by the skunks appears to have entered the makeup air units and spread through the building. This odor dissipated over time and the building was deemed safe by both BNC staff and the Purdue University Fire Department and was reoccupied. For those unfamiliar with skunks, the following quote from Wikipedia describes the discharge: "(Skunks) produce a mixture of sulfur <http://en.wikipedia.org/wiki/Sulfur> -containing chemicals (methyl <http://en.wikipedia.org/wiki/Methyl> and butyl <http://en.wikipedia.org/wiki/Butyl> thiols <http://en.wikipedia.org/wiki/Thiol> ) that has a highly offensive smell that can be described as a combination of the odors of rotten eggs <http://en.wikipedia.org/wiki/Egg_%28food%29> , garlic <http://en.wikipedia.org/wiki/Garlic> and burnt rubber <http://en.wikipedia.org/wiki/Rubber> . The odor of the fluid is strong enough to ward off bears <http://en.wikipedia.org/wiki/Bears> and other potential attackers, and can be difficult to remove from clothing. Muscles located next to the scent glands allow them to spray with high accuracy as far as 2 to 3 metres (7 to 10 ft). The smell aside, the spray can cause irritation and even temporary blindness, and is sufficiently powerful to be detected by even an insensitive human nose anywhere up to a mile downwind." It is certainly understandable that this odor could be thought to be caused by a hazardous material, and the evacuation was justified to ensure the safety of all personnel. There were also reports of a haze/fog in the building by some people, but others reported that they saw no haze, just smelled the offensive smell. The cause of this haze has not been determined, and action is being taken to determine if this was caused by lighting conditions. The gas monitors - toxic, flammable, and refrigerant - registered no elevated levels, other than the NO2 sensor which would register the thiol levels from the skunk(s). As a safety precaution, all NO2 was shut off at the cabinet, and the levels continued to increase to a stable point for an extended period of time. This indicated that the reading was indeed caused by something other than the gases in the building. Additionally, levels of all gases were checked and none showed a drop in volume as would have occurred had it been a gas leak. The building was re-opened at approximately 1:00 AM on Sunday. Because of the time of night, notifications of building closure and reopening were not sent out. Due to some confusion on Sunday morning, an e-mail to BNC-All was sent out assuring occupants that the building was open. This communication procedure is being reviewed by BNC leadership to determine whether notification should be initiated in this type of situation. A special thanks is extended to all those who responded to the emergency and ensured the safe reentry of the facility. John Weaver John R. Weaver Facility Manager Birck Nanotechnology Center Purdue University (765) 494-5494 jrweaver@purdue.edu