GROWING GOURMET - Anto2ni.it

466 DESIGNING AND BUILDING A SPAWN LABORATORY
doorway to remove debris from the feet.
With ultra-modem clean rooms, a double
door anteroom, called a "Decontamination
Chamber", utilizes the down-flow of HEPA
filtered air over the worker who stands on a
metal grate. The air is pushed from above and
actively exhausted through the floor grate to
the outside. The principle concept here is
valid: the constant descension of airborne
particulates improves laboratory integrity.
Another variation of this concept is the replacement
of the solid inner doors with
down-flowing air curtains. However, decontamination
chambers and air curtains should
be the last projects on a long list of other priorities
for the financially conservative
investor.
4) Interior surfaces not biodegradable.
Interior surfaces such as the walls, countertops,
shelving, etc. should not be able to
support mold growth. Wood and sheet rock
should be avoided. The floors should be
painted several times or overlaid with a chemically
resistant, cleanable mat. When using a
paint, use a non-mildewing enamel. (Caution:
Do not use paint containing fungicides, particular
any containing tributyl tin oxide, an
extremely dangerous toxin to both humans and
mushrooms.) Counter-tops can be made of
stainless, steel or a hardened laboratory grade
formica. The shelves storing the incubating
bags should be wire meshed, and not solid, so
that the heat generated from incubation is dissipated.
Petri dish cultures can be stored on solid
shelves.
5) Walls and ceiling well insulated. Ambience
of temperature is critical for maintaining a
laboratory. Temperature fluctuation causes two
problems. When temperatures within the lab
radically change from day to night, condensation
forms within the spawn containers and on
the upper, inside of the petri dishes. These water
droplets will carry otherwise-dormant
contaminants down to the rich media. Bacteria
particularly love condensation surfaces. When
a laboratory is run at 50% relative humidity and
750 F. (24° C.) condensation should dissipate
within 24 hours after autoclaving. The other
problem caused by temperature fluctuation is
that the outer walls of the laboratory, especially
those made of concrete, sweat. I had one small
home laboratory that grew an enormous colony
of white mold on a painted, white cinder block
wall. The whole laboratory contaminated despite
my best efforts. Only when I washed the
wall did I find the source. If your only option is
a laboratory with an outside facing cinder
block wall, make sure the pores have been
sealed with a thick coat of paint and permanently
place an electric, baseboard heating unit
facing the wall to eliminate the possibility of
condensation.
6) Lights covered with dust-proof covers.
Fluorescent lights should be covered with lens
coverings. Uncovered lights ionize particulates
which will collect as dust layers on oppositely
charged surfaces. Over time, a habitat for contaminants
builds. Ionizers are similar in their
effect and are greatly over-rated. (See Consumer
Reports, Oct. 1992.)
7) Remote vacuum cleaning system. Since
constant cleaning must occur throughout the
inoculation process, having the ability to
quickly pick up spilled grain and sawdust
greatly enhances the ease of inoculation. When
inoculations are done quickly, the likelthood of
airborne fall-out (primarily from the cultivator)
is minimized. Brooms should never be used in
the laboratory. Wet/dry remote vacuums run
the risk of clogging and then breeding contaminants.
Therefore, a "dry" remote vacuum
system is recommended.
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