Dennis
Murphy
Pennsylvania State University Cooperative Extension
We have
all heard the old saying, "a little knowledge is a dangerous
thing." This is true of many aspects of farming, and in particular
with silo gases. In fact, where these gases are involved we
ought to add that "No knowledge can be fatal." Although accidents
caused by silo gases may not occur as often as other kinds
of farm accidents, they are and will continue to be a very
real hazard for as long as silage remains a common livestock
feed. Because of this it is important that every farm worker
understand the danger associated with silo gases and how to
deal with them.
Silo
gas is formed by the natural fermentation of chopped silage
shortly after it is placed in the silo. Though a variety of
gases are released during this process, the type of silo in
which the forage is stored is important in determining which
gas will be predominant. For instance, in sealed silos both
nitrogen and carbon dioxide gases are created, but carbon
dioxide is produced in far greater amounts. This is desirable
because high carbon dioxide levels help to maintain high quality
silage. At the same time, however, this odorless and colorless
gas is dangerous. This gas replaces the silo's oxygen, and
in high concentrations, it gives a person little warning that
he is about to be overcome. Because of this hazard, sealed
silos are designed in such a way that entering them is unnecessary.
A variety
of gases are also formed in conventional or open-top silos
but in these, nitrogen dioxide is found more abundantly. This
highly toxic gas is characterized by a strong bleach-like
odor and low lying yellow, red, or dark brown fumes. Unlike
carbon dioxide, nitrogen dioxide levels reach a peak about
three days after harvesting and rapidly begin to decrease
thereafter, particularly if the silo is ventilated. After
two weeks it is unlikely that more gas will be produced, although
some hazard remains if the gas has not been able to escape
the silo.
Nitrogen
dioxide is harmful because it causes severe irritation to
the nose and throat and may lead to inflammation of the lungs.
However, what makes this gas especially dangerous is that
low level exposure to it is accompanied by only a little immediate
pain or discomfort. Though death can occur immediately, a
farmer might breathe the gas without noticing any serious
ill effects and then die in his sleep hours later from fluid
collecting in his lungs. Also, many victims suffer relapses
with symptoms similar to pneumonia two to six weeks after
the initial exposure. For these reasons, it is extremely important
for anyone who is exposed to this gas, even a short time,
to seek immediate medical attention.
Like
carbon dioxide, nitrogen dioxide is heavier than air. Because
of this, as it is produced it tends to settle right on top
of the silage or flow down the silo chute and collect in the
adjoining feed rooms or other low lying areas near the base
of the silo. Gas may even flow into the barn itself and become
trapped in corners, under feed bunks, or lie low against the
floor. The threat that this poses to livestock is a serious
one. To prevent silo gases from poisoning your livestock,
provide good ventilation wherever possible in and around the
silo when silage is fermenting. It is important, too, that
the door between the feed room and the barn be kept closed.
Safety
of your family is more important than that of the livestock.
Children should be of special concern, because the silage
operation is often a fun event for them. It may be difficult
to keep them away from the silo during its filling or for
the two weeks when dangerous gases are present. Therefore,
it is essential that the seriousness of this hazard be clearly
communicated to each family member. But do not rely on this
warning alone. Since you know best the layout of your silo
areas, do what you think is necessary and reasonable to keep
young ones from straying into them. This could mean padlocking
doors, or in some instances, even placing fences or barricades
in needed locations.
Ideally,
every farmer should also avoid the silo during the critical
period when gases are forming. With the enclosed silo this
is easily done. Unfortunately, it is not always so easy to
keep away from a conventional silo, for machinery breaks down,
chute covers must be put on, and filling the silo is usually
not accomplished in one cutting. Because entry into these
silos sometimes becomes necessary while nitrogen dioxide might
be present, it is best to use a self-contained breathing apparatus.
This is the only breathing device that is certain to protect
you from all silo gases. Do not expect dust masks or even
chemical cartridge respirators to provide sufficient protection.
Neither is intended for use where gases are extremely toxic
or where the air has been replaced by gases such as carbon
dioxide. Unfortunately, the intricate components which make
the self-contained breathing apparatus (SCBA) effective against
silo gases also makes it expensive to buy. Nor are self-contained
breathing apparatuses easy to fit or use without proper training.
If you
do not have a self-contained breathing apparatus, stay out
of the silo during the first 2-3 days after filling. If you
must enter the silo after the first few days, it can usually
be done safely if the following precautions are observed.
First, ventilate the silo and all adjacent areas thoroughly
before entering. This can be done by running the silo blower
for fifteen to twenty minutes before going into the silo,
by opening all upper chute doors down the level of the settled
silage, and by opening the windows in the feed rooms. The
blower should remain in operation for the entire time you
are inside. An important thing to remember is that the lower
the level of silage in the silo, the greater the risk that
the ventilation from the silo blower is insufficient to adequately
dilute the silo gas. In other words, there is no guarantee
that silo blower ventilation will make it safe for you to
enter the silo without a self-contained breathing apparatus.
Next,
you should never enter a silo unless another person is present,
one who could go for help should you need it. This person
should maintain visual contact with you. If gases are present
you may not have a chance to call out before becoming unconscious
or other sources of noise may drown out your attempts to gain
someone's attention. Finally, though it will not protect you
from silo gases, wear a dust mask or some other respirator
to protect your lungs from the high concentrations of dust
and mold spores which are found in silos.
Preventing
accidents caused by the inhalation of silo gas is, in theory,
very simple. Whether or not this is true in your experience
depends upon your willingness to practice these safety tips.
- Keep
children away from the silo and adjoining area for at least
two weeks after silage has been put in the silo.
- Close
the feed room door to the barn.
- If
entry into a silo becomes necessary you should
-ventilate all silo areas, -get the help of a second adult,
and -wear a dust mask.
Regard
silo gases as a real hazard NOW! Don't wait until you become
a statistic.
Disclaimer
and Reproduction Information: Information in NASD does not represent
NIOSH policy. Information included in NASD appears by permission
of the author and/or copyright holder. More
NASD Review: 04/2002
Author:
Dennis Murphy, Associate Prof. Ag. Engr.
Department of Agricultural Engineering, Penn State - July 1988
- PENpages Number:
0870194
The
National Dairy Database (1992)
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