Baseboard Air Purge Valves

Hello, I have a hot water heating system that runs on a tankless high efficiency boiler. Around the house I have cast iron baseboards. As we get ready for winter I wanted to make sure there is no air in the system (had to drain it over the summer to replace the indirect hot water tank). On each of the baseboards there appears to be an air purge valve. However, aside from the fact they are extremely rusted/calcified they are all already turned to the "open" position.

I'm assuming that means the air can escape at all times and no need to check if there is air within the system? Or should these valves not be constantly turned to the open position and the rust/calcification is blocking any path for the air to escape?

Ignore the landlord special paint job :)