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floor. After a minute or two, the cultivator, reenters
the lab and begins his routine. (Note that
you should not mix disinfectants—especially
bleach and ammonia. Furthermore, this
method can potentially damage your lungs or
exposed mucous membranes. Appropriate precautions
are strongly recommended.)
Without the exchange of fresh air, carbon
dioxide levels will naturally rise from out-gassing
by the mushroom mycelium. As carbon
dioxide levels elevate, contaminants are triggered
into growth. An additional problem with
heavily packed spawn rooms is that with the
rise of carbon dioxide, oxygen levels proportionately
decrease, eventually asphyxiating
the laboratory personnel. Unless the air is exchanged,
the lab becomes stifling and
contamination-prone. Since the only way to
exchange air without introducing contaminants
is by filtering, the combination of fans
and micron filters is the only recourse.
Other cultivators use ultraviolet lights
which interfere with the DNA replication of all
living organisms. UV lamps are effective when
the contaminants are directly exposed. However,
since shadowed areas are fully protected
from UV exposure, contaminants in those regions
remain unaffected. I disdain the use of
UV in favor of the micron filter alternative.
However, many others prefer their use. Note
that the lab door should be electrically
switched to the UV light so that the lamp turns
off at entry. Obviously, exposure to UV light is
health-threatening to humans, potentiating
skin cancer and damage to the cornea of the
eye.
Frequently, the vector of airborne contamination
is easy to detect because of the way it
forms on petri dishes. Airborne contaminants
enter a petri dish either at the time the lid is
opened (during pouring or inoculation) or dur-
THE SIX VECTORS OF CONTAMINATION 77
Figure 58. Using an elastic film to seal the top and
bottom of petri dishes. This eliminates the chance
of airborne contamination entering during incubation.
ing incubation. When the dish is opened, airborne
contamination can spread evenly across
the face of nutrient media. During incubation,
contaminants creep in and form along the inside
periphery of the petri dish. This latter
occurrence is most common with laboratories
with marginal cleanliness.A simple solution is
to tape together the top and bottom of the the
petri dish directly after pouring andlor inoculation
using elastic wax film. (Parafilm® is one
brand. See Figure 58.) Plastic, stretchable
kitchen wraps available in most grocery stores
also can be used. These films prevent entry of
contaminant spores that can occur from the fluctuation
of barometric pressure due to natural
changes in weather patterns.
One helpful tool in eliminating each vector
of contamination as the source is to leave con-
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