My furnace and water heater are located in a separate small room inside my finished basement, the small boiler room dimensions are 7ft x 7 ft x 5 ft with a solid metal door. In order to provide fresh air for proper combustion of the heating system, I opened an eight inch in diameter hole through the exterior wall and installed a duct fan which I connected to the furnace to draw air into the room. The wiring works well, every time the boiler runs, the duct fan will also start and bring fresh air from outside into the room.
My questions are the following, Is this system adequate to bring enough air into the room?
Do I need to install something else? Are there any safety concerns that I should be aware of?
Thank you in advance.

Kafur