I have to say, this is one of those "I had no idea." If you happen open up your mail box in Bismarck Mandan this summer, and find a dryer sheet in your mailbox, don't freak out. You haven't been targeted by a gang or anything like that. Your mailman isn't trying to send y...
for example, used hypocaust systems to heat their baths and homes, employing flues to circulate warm air. However, systematic cleaning of air ducts and vents did not become prevalent until the development of modern heating and cooling systems in the 20th century. ...