Hood assembly

In an enclosure having a substantially horizontal floor, a pair of spaced end walls a substantially vertical back plate extending between said end walls, a forwardly extending hood, a housing intermediately disposed between said back plate and hood, and a stack extending upwardly from said housing, the improvement for preventing minute air borne particles in said enclosure from escaping through an opening in the forward portion of the latter into the room in which said enclosure is situated, said improvement comprising:

• a. single power driven blower means in said housing, said blower means having an air inlet and an air discharge;
• b. a back wall that extends downwardly from said air inlet forwardly of said back plate and cooperating therewith to define a first passage in communication with said air discharge;
• c. first means that cooperate with said back wall to define an upwardly directed opening adjacent said floor;
• d. a forward wall that extends forwardly from said air inlet and downwardly spaced from said hood to cooperate with the latter to define a second passage in communication with said air discharge, and said forward wall and hood also cooperating to define a second opening that is directed downwardly and rearwardly at an angle;
• e. air borne particle removing means that extend across said air inlet;
• and
• f. first adjustable damper means in said stack, said blower means when operating concurrently discharging pressurized air to said stack and said first and second passage, said pressurized air delivered to said first passage discharging from said first opening as a first high velocity air stream along the forward surface of said back plate to create a negative pressure towards which said minute air borne particles tend to move to become entrained with said first stream and be separated therefrom as said first stream flows through said removing means, said pressurized air discharging from said second opening as a downwardly and rearwardly directed second stream that tends to move said minute air borne particles not already entrained with said first air stream rearwardly to so become, said air inlet of said blower maintaining a negative air pressure above said removing means to encourage the flow of said first and second air streams therethrough, said first damper means regulating the magnitude of the rate of flow of air from said enclosure and the room surrounding the latter through said stack to the ambient atmosphere, and said first damper means when closed causing said blower means to recycle air to remove said minute air borne particles therefrom without removing air from a room in which said enclosure is situated.