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Brewery ventilation rate

  1. Jul 27, 2013 #1
    Hi All, I'm designing an exhaust system in brewery. Does anyone know the recommended air changes (ventilation rate)? My concern is the elevated level of carbon dioxide during the fermentation process. I'm planing on exhausting the air thru sidewall propeller fans and make-up the air thru roof mounted gas heated make up air fan. Please Advice.
  2. jcsd
  3. Jul 27, 2013 #2
    For the US
    http://www.lni.wa.gov/WISHA/Rules/AirborneContam/default.htm [Broken]
    and clicking on Scope and then in table 3 for carbon cioxide
    one obtains 5000ppm exposure limit

    Also same site but another page

    So you have to ventilate to keep the CO2 level below that number if employees are in the area.
    Last edited by a moderator: May 6, 2017
  4. Jul 27, 2013 #3
    ASHRAE has a standard of 1,000 ppm CO2 for indoor spaces. how do i keep it down in my exhaust design
  5. Jul 27, 2013 #4
    Well yes. Anything above 5000ppm and a person can suffer oxygen deprivation or other toxic effects with extended exposure. Below 1000ppm is the comfort zone so that headache, nausea, drowsiness do not occur for most people. That is the difference.

    If you have people in the workspace continiously then use the Ashrae figure.
  6. Jul 27, 2013 #5
    I am not a brewery guy nor an air ppm concentration guy but here goes as to what I think.

    First thing you should do is determine the rate of CO2 production by the the yeast is the vat, say cubic meters per hour.
    Let that rate be Xyeast.

    You are exiting nXout; where Xout is the amount of CO2 in the room air per cubic meter, and n is the number of cubic meters per hour exiting.
    Input air is similar nXin; here Xin is the amount of CO2 in the incoming air per cubic meter, and n is the amount of air entering in cubic meters per hour.
    The room has Xroom amount of CO2 per cubic meter.

    You want to keep Xroom below that related to the 1000ppm.
    And at steady state, Xroom = Xout.

    Xroom = Xroom - nXout + nXin + Xyeast

    That gives you a general idea of what is going on with the ventillation.
    ( Of course , the voume of incoming air is less than the outgoing air due to the gas production by the yeast, so in reality nin < nout )

    If you fiddle around with that and tidy it up somewhat making sure I did not forget or misrepresent any items, then you can relate that to the desired ppm. Perhaps through some iterations you can obtain an air change. One would think though there should be a standarized method to obtain air changes if one knows the rate of production of a gas source which the fermentation process is.
  7. Jul 30, 2013 #6
    456.3587 Total pounds of co2 released per day at full capacity. please help how many Air changer per hour required to be exhausted.
  8. Jul 31, 2013 #7
    A a very high precision you have with 456.3587 pounds of CO2. Let's just round that up to say an easier figure like 460 pounds or 220 kgs. How you came to a value is pounds would be interesting to know.

    So, calculate the volume of air at 1000ppm CO2 content contains 220kg or 360pounds of carbon dioxide. Ventilating that much air would be a suitable figure to work with to size your fan(s).
  9. Aug 1, 2013 #8


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    A dumb question: why would you want to release 200 kg of CO2 per day into the atmosphere of the brewery, and then remove it by changing the air?

    Wouldn't it be better to vent the CO2 from the fermentation vat directly outside the building? Or is this an "artisan" type of microbrewery that is using open fermentation vats (with the disadvantages of contamination from airborne material, though some people prefer them for top-fermenting yeasts) rather than closed vats?
  10. Aug 2, 2013 #9
    Not a dumb question.
    The brewery is most likely operating with venting from the vat directly to the atmosphere. That would be the most sensible way to do it. Venting into the inner space would require a larger ventillation system, and pockets of CO2 could be trapped in certain areas unless adequate air circulation was guaranteed, and also temperature control of the vat and inner space would be problematic.

    My thought process was to calculate the maximum ventillation required IF the CO2 was vented into the building and then scale that back to perhaps 1% to 2% ( assuming anything more than that and his system is not well contained, though the operator would have to use a percentage value better to his liking and experience ). Comparing that value to the size of building and the volume of air within, the brewery operator could obtain a reasonable air exchange value.

    With 220kg of CO2 released per day from the vat, a 1% seepage would mean a 2.2kg of C02 collection into the inner area. With a nominal air density of 1kg/cubic meter, outside air containing 400ppm C02, a thorough mixing with (approximate) 4400 cubic meters of outside air per day should suffice to obtain the desired 1000ppm of C02 within the inner space.

    Though I do hesitate(d) for the brewery operator to to actually use that figure as being totally reliable, since first hand site observation from a professional in his area should provide a better assurance that other extraneous factors are taken into account.
  11. Aug 2, 2013 #10
    that should have read:
    Ventilating that much air would be a suitable figure to work with to size your fan(s) if you consider a seepage value into the inner work space.
    which still does not make sense.
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