How many letters does the top answer for “the act of supplying fresh air and getting rid of foul air” have?

The most common answer is airing (6 letters).

Crossword clue: the act of supplying fresh air and getting rid of foul air

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

airing 6 letters wn-def

the act of supplying fresh air and getting rid of foul air

ventilation 11 letters wn-def

the act of supplying fresh air and getting rid of foul air