GROWING GOURMET - Anto2ni.it

476 THE GROWING ROOM
pacity. Air is first filtered through a standard
Class 2 pre-filter. These filters are relatively
coarse, filtering particles down to 10 microns
with 30% efficiency. Pre-filters are disposable
and should be replaced regularly, in most cases
every one to three months. The next filter is usually
electrostatic. Electrostatic ifiters vary
substantially in their operating capacities and
airflow parameters Typically, particulates are
filtered down to 1 micron with 95% efficiency.
Electrostatic filters can be removed, periodically,
for cleaning with a soapy solution. Their
performance declines as dust load increases. For
most growing rooms of 10,000 to 20,000 cubic
feet, a 25 x 20 x 6 in. electrostatic ifiter suffices
when combined with a fan sending 1000-2000
cubic feet per minute airstream into each growing
room. See Figure 390 for the location of these
filters.
9) Filtration of recirculated air Recirculated
air from a growing room is relatively free
of airborne particulates during the colonization
phase. When the cropping cycle begins, the air
becomes thick with mushroom spores. (This is
especially the case with Oyster mushrooms
and much less so with Button mushroom cultivation.)
I have seen the spore load of Oyster
mushrooms become so dense as to literally
stop the rotation of high volume cfm fans!
The design of an air system should allow partial
to full recirculation of the air within the
growing room. Usually, a recirculation duct is
centrally located directly below the incoming
air. A damper door controls the degree of recirculation.
If the recirculated air is passed through
filters, these filters will quickly clog with mushroom
spores, and airflow will radically decline.
If electing to use filters, they should be changed
every day during the cropping cycle. A simple
way of cleaning the recirculated air is to position
mist nozzles in the recirculation duct-work.
Figure 396. Close-up of air supply system for growing
rooms featured in Figure 393. Air enters from
below, passing through a coarse and an electrostatic
air filter. A large squirrel cage blower pushes air into
main duct system where two "rain trees" allow the
introduction of cold or hot water into the airstream.
In-house thermostats coupled to solenoid valves
regulate the cold or hot (steam) water supply. Recirculation
shutes enter the plenum from the side. The
degree of recirculation can controlled within the
growing rooms. Pre-conditioning the air quality to
70-80% of desired levels is recommended before entry
into the growing rooms. Provisions for excess
condensation must be engineered into system.
The air will be largely rinsed clean of their spore
load from the spray of water. Ideally, these
downward-flowing nozzles are located directly
above a drain. Having spray nozzles located below
the inside roof line and misting downwards
will also facilitate the downward flow of spores
to the floor. This concept can have many permutations.
10) Humidification With the 6-12 air ex-
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