200 B.C. – FIRE-HEATED FLOORS AND SMOKY SUPPLY AIR
Perhaps the very first steps towards present-day ventilation can be attributed to the Greeks who were the pioneers of the so-called hypocaust system (from the Greek meaning ‘under’ and ‘burnt’). Wood-burning furnaces were sited below floor level and the resulting hot air and smoke would find its way out via smoke ducts in the floors and walls before being led out through rooftop chimneys. After the fire had burnt out, small floor hatches were opened, releasing warm air into the rooms above. It is doubtful whether the hypocaust system can be regarded as a true ventilation system.
And the warm air released into the rooms after the fires had gone out was smoky and most probably unpleasant to inhale. It was not until much later, however, that the idea of using rising hot air was used successfully for more specific ventilation purposes.
The Middle Ages – MEDIEVAL CHURCHES WITH HIGH CEILINGS
In buildings with very high ceilings, and especially in churches, there is an enormous volume of air and it would take a long time before it became polluted, perhaps longer than the time needed for a service. In this case, warm polluted air would rise up towards the roof to be released at a great height through openings in the bell or clock tower.