WordNet sense 1 (free and open discussion of (or debate on) some question of public interest):

public discussion

WordNet sense 2 (a mechanical system in a building that provides fresh air):

ventilating system, ventilation system

WordNet sense 3 (the bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation):

breathing, respiration, external respiration

WordNet sense 4 (the act of supplying fresh air and getting rid of foul air):

airing