In 1970, when I started in the heating industry, there was a battle going on between the folks who believed in catching and controlling the air in a hydronic system by holding it inside a plain-steel compression tank, and those who thought it was best to catch the air and just get rid of it using automatic air vents and diaphragm-type compression tanks.
The question was in the Manchester Evening News, a British newspaper, and it caught my eye when I was going through my daily Google Alerts on things that have to do with heating.