English: MECHANICAL VENTILATION ON THE DOWNDRAUGHT SYSTEM, BY IMPULSION, OR THE 'PLENUM' PRINCIPLE, APPLIED TO SCHOOLROOMS.

• A Roof Ventilator.
• B Main Upcast Shaft.
• C Horizontal Foul Air Trunk.
• DD Connecting Pipes from Foul Air Flues.
• EE Foul Air Flues.
• FF Foul Air Exits into Flues EE.
• GG Fresh Air Supply Flues through which the air is mechanically projected at a high velocity up on to the ceiling and then descends, escaping at Exits FF into Flues EE.

N.B. The fresh air supply heated to such a temperature, as is necessary to effectually warm a building, is thereby seriously deteriorated for breathing purposes, therefore to secure healthy ventilation the heating of a building should always be separate and distinct from that of the air supply.

• BLUE Fresh air supply.
• YELLOW Products of combustion.
• BROWN Products of respiration.
• RED Products of respiration from infected scholars.