Fresh air inlets do not assure fresh air to the space. The amount of fresh air is determined by the pressure on the the opening. Wind will cause a negative pressure on your fresh air inlet whenever the opening in downwind on your home. To assure fresh when needed, get 4" duct fan that operates whenever the boiler heates. Much needed fresh air to your home functions the same way.
In your home, you get any fresh air is when the wind blows. Ideally, you should have an air change in 4-5 hours to purge indoor pollutants and renew oxygen for the occupants. Unfortunately, humanes show soot when they get inadequate fresh air.
An adequate fresh air supply to the home should operate when the home is occupied or the burnner runs.
Most people have no idea how important fresh air is to the home.
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"