airing vs volunteering

airing

noun
  • A public expression of an opinion or discussion of a subject. 

  • The broadcast of a television or radio show. 

  • An exposure to warm or fresh air. 

volunteering

noun
  • The act of voluntarily giving time and labor for charity or community service. 

How often have the words airing and volunteering occurred in a corpus of books? (source: Google Ngram Viewer )