Which biosafety levels require placement of biohazard sign on the door?

BiOSafety levels 2, 3, and 4 require the placement of a biohazard sign on the door of the laboratory. This signage is essential to inform personnel and visitors about the potential risks associated with the pathogens handled within these facilities. The sign typically indicates the specific biOSafety level and outlines necessary precautions. Level 1 labs do not require such signage as they deal with minimal risk agents.