All fuel-burning boilers require adequate amounts of combustion air. Most atmospheric boilers also required air circulation to carry away heat loss from boilers’ jacket and flue piping.
The manner in which this air is provided is governed by building and mechanical codes, and those codes typically reference NFPA 54. The 2018 version of NFPA 54 prescribes methods for providing this air into confined spaces using one or two openings to outside space.