ICBW, but I believe the term “cold air” is being used relative to the temp of steam. A boiler does not run constantly and between cycles, the air in the system cools down, but does not get cold. When the next cycle starts, the air in the system is already warm and moist thanks to the condensate the system.
That makes sense... It certainly will at least be saturated.
” the air in the system cools down, “
After you bleed the system their should be no air in the system.
“A boiler does not run constantly and between cycles, the air in the system cools down,”
The boiler cycles to maintain temperature in the system. The system never cools down.