What characteristic distinguishes a laminar flow workstation from a Class I or Class II biosafety cabinet?

A laminar flow workstation is specifically designed to provide a sterile environment by circulating air in a unidirectional flow, directly protecting the materials being handled rather than the operator. This design typically features an open front, which distinguishes it from Class I or Class II biosafety cabinets that have a front window or sash to protect the user from potential exposure to biohazards.

In Class I biosafety cabinets, not only is the airflow system designed to provide personnel and environmental protection, but they also have a front window or sash that creates a barrier between the user and the work area. Similarly, Class II cabinets, which are more advanced, provide both personnel and product protection while maintaining a controlled airflow, which also requires a front sash.

The absence of a front window in laminar flow workstations means that they do not provide the same level of personnel protection against hazardous agents as the biosafety cabinets do. Instead, they prioritize the sterility and safety of the samples being handled, making option B the most accurate distinguishing feature.