Back in the day, air conditioning referred to heating the air as well as cooling it. Air conditioners had four main functions: temperature control, humidity control, circulation and cleaning. Instead of using condenser and cooling coils, the way modern air conditioners do, this one used a complicated system of spray nozzles and water pans to adjust air temperature.
While we typically install air conditioner units over small windows, this humidifier was designed to fit over a warm air furnace. You could either purchase a complete system, or you could attach individual air filters, blowers, or automatic auxiliary humidifiers to an existing heater. And if your home didn't warrant an expensive air conditioner, you could always opt for a portable space cooler, which typically consisted of a wheel-bound machine that blew air over a block of ice.
Read the full story in "Manufactured Weather for the Home"