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The above images show equipment inside one of Ohio State University's current biosafety level 3 laboratories following a recent refurbishment of facilities. Most work with biological agents within the lab is performed inside one of the special containment hoods shown in each picture. These hoods operate at negative air pressure -- as does the entire lab itself -- insuring that pathogens cannot escape to the outside. There has never been a release of any pathogenic agent from any biosafety level 3 laboratory, or at biosafety level 4 laboratories elsewhere in the country, according to university officials. Photo courtesy Jo McCulty, University Relations, Ohio State University.