Biosafety cabinets (BSCs) and fume hoods are both used in laboratories to provide a safe working environment, but they have different purposes and features:

1. Purpose:

 Biosafety Cabinets: Designed to provide both a clean work environment and protection for employees who work with biological hazards. BSCs are used when working with infectious agents or biohazardous materials. They have a HEPA filter to protect the lab environment and the user from harmful biological agents.

  Fume Hoods: Primarily used to protect the user from inhaling hazardous chemicals and vapors. They are not typically used for protection against biological hazards. Fume hoods work by drawing air away from the user and exhausting it to the outside.

2. Airflow and Filtration:

Biosafety Cabinets: Have a more complex airflow pattern and HEPA filtration system. Air is filtered both as it enters and as it exits the cabinet, which provides environmental, product, and user protection.

 Fume Hoods: Do not typically filter the air but instead work on the principle of dilution and exhaust. Air is drawn away from the user and expelled outside the building.

3. Protection Level:

Biosafety Cabinets: Offer a higher level of protection for handling pathogens and biohazardous materials. There are different classes of BSCs (I, II, and III), each with specific performance criteria and protection levels.

 Fume Hoods: Primarily protect the user from chemical fumes and vapors but do not provide the same level of protection against biological hazards.

4. Usage:

Biosafety Cabinets: Used in microbiology, virology, cell culture, and in any application where clean, sterile conditions are required.

Fume Hoods: Used in chemistry, pharmaceutical, and industrial laboratories where handling of toxic or noxious chemical agents is required.

In summary, biosafety cabinets are designed for working with biological hazards and provide a sterile environment, whereas fume hoods are designed for working with chemical hazards and primarily protect against inhalation exposure. The choice between a BSC and a fume hood depends on the type of work being performed and the nature of the hazards involved.