Controlling Spore Load in Fruiting Chamber with Mist

Discussion in 'ADVANCED MYCOLOGY' started by ThunderFarm, Feb 20, 2017.

  1. ThunderFarm

    ThunderFarm Member

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    Hello all, I am new to this forum. I am designing a small commercial oyster mushroom farm. I plan to post my comprehensive design when it is complete. My initial fruiting chamber will be 10ftx12ft by 8 feet high. I have read a number of books and read thousands of forum posts, but cannot find information on reducing spore loads in fruiting chambers using misters. In Paul Stamets 3rd edition of Growing Gourmet and Medicinal Mushrooms, pg 486, he suggests using misters in the recirculating ducts to wash the spores out of the air and place the duct over a drain.

    However, there is not much detail in his book and as we know, the devil is in the detail. Therefore, I am proposing the following system and would appreciate any feedback, both positive and negative, and alternatives.

    1. Horizontal 4-inch PVC pipe (i.e., air duct) ring at the intersection of the wall and the ceiling around the entire room.
    2. Continuously running recirculating fan: Vortex VTX400 Vortex 172 CFM Powerfan, 4", with speed controller to obtain desired air exchange rate. Please note I will have a separate system for fresh air input.
    3. In one corner, I will have a vertical 4-inch PVC air duct connected to the horizontal duct at the ceiling. I will install a mister towards the top to flush the spores with the water/mist. This duct will go through the floor (or wall) and exit the building, thus acting as a drain for the water/spore mixture.

    On advantage to this system is the misting duct/drain will operate continuously and thus will always be under positive pressure preventing flies and other insects from entering the drain. This will also reduce the spore load, which will increase the life of the circulation fan as well as the window air conditioner fan and filter.

    One last question, how many times per hour should the fruiting chamber air be recirculated? Please note that this is independent of the amount of fresh air needed to maintain the appropriate CO2 level.

    Thank you in advance for your input and suggestions.
     
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  2. FallenOak

    FallenOak Mushroom Cultivator Mushroom Doctor

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    Welcome to the forum @ThunderFarm!

    I have a few question about your design idea. Where will the spore laden air be drawn in? Are there holes spaced evenly in the pvc? And how will the fan fit into this if the ring is continuous around the ceiling? Will there be another tee off at the corner with the mister/drain pipe?

    Very interesting ideas, but in my opinion it is overkill for a space as small as you are proposing. Most small indoor farms, including mine, use cheap short lengths of exhaust air ducting that gets replaced periodically as spores and gunk builds up.

    I think you should focus more on making your space easily cleanable, i.e. waterproof everything and provide a drain in the floor. We spray out our rooms often from tip to toe with an iodine solution mixed in a hose end fertilizer mixer.

    As far as recirculating room air goes, air movement is a must, but constantly recirculating the air is not necessary, again especially with the small space you are proposing. You should be focused more on being able to provide enough fresh air exchanges while keeping your humidity high. Many of these "requirements" Paul Stamets talks about are more applicable to very large warehouse type fruiting rooms that have full scale air industrial handling systems and mostly permanent ducting.
     
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  3. ThunderFarm

    ThunderFarm Member

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    FallenOak,

    Thank you very much for your response.

    1. Where will the spore laden air be drawn in? In the corner of the room at ceiling height. The ceiling is flat and thus i was concerned with preventing condensation on the ceiling and getting stagnant air pockets.

    2. Are there holes spaced evenly in the pvc? I have not determined the size or spacing of the holes yet, but i plan on making the holes closer to the fan smaller to get approximately the same air from each hole around the room.

    3. And how will the fan fit into this if the ring is continuous around the ceiling? I plan on using an inline fan.

    4. Will there be another tee off at the corner with the mister/drain pipe? Yes, the drain pipe will be put into a tee.

    I am starting out small, but hope to expand my operation depending upon the market and if it is has an acceptable level of profitability. Thus, i was using this small fruit chamber to test my ideas. Thank you for the advise, i really appreciate it. I plan on using FRP panels, a floating (optional glue type) vinyl flooring and a drain to allow me to hose down the room periodically. Also, all the electrical controls will be in another room and the light fixtures will be waterproof. How often do you spray your room with your iodine solution? What strength? Do you only spray with an empty room or do you have substrate growing at the time?

    I can easily setup the recirculation fan on a timer and adjust the system using the timer and if needed adjusting the fan speed. I guess trial and error on how much recirculation to use.

    I am concerned with the oyster mushroom spores clogging up the air conditioner fan, thus requiring cleaning, the inline fan too. I was also thinking about cutting some MERV 11 or 13 filter pieces and replace the existing window air conditioner air filter, but without removing most of the spore load i figured i would be changing these filters daily at times. Also, this will increase the resistance and thus result in less air flow, but i have purposely over sized the air conditioner. I am wondering if this would increase or decrease the chance of the air conditioner freezing? Probably increase?

    How do the short sections of exhaust air ducting prevent the fans from getting spore buildup?

    My current plan is to have the humidity controlled separately, along with the fresh air input using a CO2 monitor. The AC and heat will also be controlled using thermostats. There is so much information and differing opinions on ultrasonic foggers vs high pressure misters. I am uncertain how to proceed on the humidity design.

    Thank you again for your time!
     
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  4. FallenOak

    FallenOak Mushroom Cultivator Mushroom Doctor

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    Ahh, I understand now where your going with the air recirculator idea, I can envision it now, for sure.

    We spray every other week, with bags in the room. Just wheeling the shelves to one side of the room and working our way back, while mopping into the drain. We use about 1 1/2 tsp per gallon of iodophor (brand?) brewing sanitizer.

    The key to keep the spores out of your window AC (and to keep it from freezing up as well) is to house it in an adjacent small equipment room that is well insulated, then draw the pre-cooled air in through your humidifier system and other ducting if needed. We actually have a secondary stand alone AC unit in the equipment room as well, and that is hooked up to a temp controller with a probe through the wall.

    The exhaust ducting doesn't keep spores out of the CO2 fan, a coarse prefilter before the fan helps though. The ducting just gets thrown away and replaced occasionally when they get sufficiently gross with spores, and the fan should be cleaned as well.
     
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  5. ThunderFarm

    ThunderFarm Member

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    For the grow room, why not run it under positive pressure using a passive exhaust system. This would eliminate the exhaust fan, and thus the need for periodic fan cleaning. You would still need the filter and replace the exhaust duct work occasionally.

    Now that you are following my logic, is my idea of washing spores with mist still not feasible? I am still concerned with bacterial growth in the drain, however.

    I have also been designing the humidity control system using 1000 psi high pressure misters. The droplet diameter is a little bigger compared to ultrasonic misters, but this will eliminate the need to clean the ultrasonic mister water tank and eliminate a potential source of mold and bacteria. What humidity control system do you run?

    Thank you again for your input.
     
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  6. FallenOak

    FallenOak Mushroom Cultivator Mushroom Doctor

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    I think that you have this in the bag man. All your plans sound feasible, passive exhaust with co2 controlling fresh air it is a great option. I was just telling you how I built my rooms, which is with active exhaust on a timer.

    I think the plan for the spore washer is feasible, by all means try it out.

    I use ultrasonic fog, but again, to each his own. Misters would work just fine.
     
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