While both pieces of equipment are hoods with directional airflow, they function differently and are intended for different purposes. BSCs protect the investigational product as well as the user and the environment. They operate under negative air pressure (i.e., suck inward), protecting the user from exposure to aerosolized infectious agents. The air sucked into the hood is sterilized by HEPA filtration before being exhausted out, thereby protecting the environment. Clean benches or laminar flow hoods work under positive air pressure (i.e., blow outward) and are only intended for work with non-hazardous materials. Use of hazardous materials in a clean bench can increase the risk of occupational exposure and contamination of the room in which the work is being done.