This unit works on a recirculating mode with air being filtered by an HEPA filter with 99.995% efficiency on 0.3u particles, before entering the work area at a speed of 0.45 m/s; this ensures a Class 100 environment throughout the work area. Air coming through the front aperture is then mixed with the downflow air, without affecting the product, and recirculated. 70% of the air is returned to the working area through the main HEPA filter and 30% is exhausted into the environment through an exhaust HEPA filter. This ensures double protection both for the product and for the operator even if this cabinet should not be used for handling pathogens. The special sloped front design and the sliding sash ensure comfortable working position and, when needed, a very easy opening and closing of the front window.