Doorknobs and broomsticks

RESEARCHERS have shown that biometric sensors are no dirtier than doorknobs. While biometric equipment is gaining popularity in a variety of electronic security applications, many users believe the devices are unsanitary and a potential source of germs that could cause illness. Now researchers have found that although the surfaces of some biometric devices may look more unsanitary due to visible dirt and prints, they harbor about the same amount of bacteria as a typical doorknob. Christine R. Blomeke, a researcher and doctoral student in Purdue’s Biometric Standards, Performance and Assurance Laboratory, performed the study along with lab director Stephen J. Elliott, an associate professor of industrial technology, and Thomas M. Walter, a continuing lecturer in the Department of Biological Sciences. Blomeke said the study was conducted because of participant comments made during fingerprint and hand-geometry studies at the lab. She said the subjects, who were required to touch their hands or fingers to the sensors, questioned the cleanliness of the surfaces. “When you look at these devices, finger moisture, dirt and oils cause the surface to appear to be dirty,” Blomeke said. “In a study we did on this last year, more than a quarter of the participants indicated that they thought the devices were somewhat unsanitary. “Since the use of biometric devices is rapidly expanding in public spaces, such as airports, stores and banks around the world, we felt it was important to examine whether touching these surfaces would subject users to more germs than they would be exposed to by touching objects such as pens, doorknobs and elevator buttons.” For the study, Blomeke’s team examined the bacterial recovery and transfer from three types of biometric sensors: fingerprint, hand-geometry and vein-recognition devices. Each sensor was tested separately with two kinds of bacteria: Staphylococcus aureus, a common cause of blood and skin infections, and Escherichia coli, commonly known as E. coli, which can cause diarrhea, urinary tract infections and meningitis. A metal doorknob was tested with the same methods. Researchers found that the transfer of bacteria from the doorknob to another surface was nearly identical to that of the biometric devices. Blomeke said that on the doorknob, as well as on the three biometric devices, the majority of bacteria was transferred within the first 10 touches. “What we can take away from this is that no matter what kind of a surface it is, if it is contaminated, the more it is touched, the cleaner the surface becomes,”