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air for combustion

Paul_69 Member Posts: 251
how can you tell if a boiler room or basement has eneough combustion air when doing routine check ups and service calls. alot of jobs i notice rooms getting enclosed after inspection.even if there is no apparent problems i would like to be able to cya and not be liuable if a problem arises after i have been there. i am a tech.


  • icesailor
    icesailor Member Posts: 7,265
    Air for Combustion:

    I haven't found a positive way to do that other than knowing that from my Massachusetts Continuing Education for my licenses, there is almost never enough to meet code. So, from there, assume that there isn't enough and go from there.

    I have found that if the appliance is in a closet with no ventilation, I can put my Fyrite Insight into the exhaust with the door open, and check the CO while running with the door open. If I close the door and the CO goes up, it needs more make-up air. My EUI CO71 remembers the highest number so if I leave that in a room with the door closed for a while, and I get a reading, I know that there is an issue.

    You touch it, you may own it.
  • Tim McElwain
    Tim McElwain Member Posts: 4,487
    edited February 2012
    Air for Combustion

    measure the size of the space lets say we have a room 40 feet by 25 feet by 8 feet high multiply 40 x 25 x 8 will give you 8,000 cubic feet of space. The rule is 50 BTU's per cubic foot so you divide 8,000 by 50 which will give you 160 which is Cubic feet per hour multiply that times the heat value of a cubic foot of gas lets say 1,000 and it comes out to 160,000 BTU's. Total up the BTU's in the space if it is less than 160,000 the space is not confined and can get its air for combustion from within the room. If it is over 160,000 it will have to get air from outdoors or from spaces communicating with outdoors. Typically that is two openings sized according to code one 12" from the ceiling the other 12" from the floor. This can be done horizontally or vertically depending how it is done affects the size requirements.

    Bottom line after all of that it has to work so you need to do testing with a combustion analyzer.

    Other options are to bring air into the space by mechanical means such as "Fan in a Can" or "Fan in a Drum".
  • Mpj
    Mpj Member Posts: 109


    Does that rule of thumb also go for oil boilers?

    I see oil boilers in small rooms (6'X6') and the techs say it is fine because the oil burner has a fan to pull air in the room. Had a boiler room 7'X7' and I installed an "air in a can" the burner guy who came to adjust the burner said the is was a waste of money and would not do a thing to help. Any opinions?

  • Tim McElwain
    Tim McElwain Member Posts: 4,487
    Those are not rules of thumb

    but they are code. Does oil burn? Does oil have BTU's? Then it needs air for combustion just like any fossil fuel so the same rules apply NFPA 31/NFPA 211 and NFPA 54 National Fuel Gas Code all talk the same way about venting and air for combustion.

    Dryers are one of the worst offenders of lack of air in a combustion zone, all dryers require "make up air" by code yet you rarely see it. They are not vented but they exhaust air so they fall under the same requirements as mechanical exhausting.

    Many licensed installers both oil and gas do not know what they are doing when it comes to this they need training.
  • icesailor
    icesailor Member Posts: 7,265

    The oil burner guy knows not of what he speaks.
This discussion has been closed.