Dennis
J. 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 (see Figure 1). 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, d 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 example: 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 (see Figure 2). 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 apparatus
s 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 two to three 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 to 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 (see
Figure 3). 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
This document
was published in 1991 as Pennsylvania State University Fact
Sheet Safety
16
, Pennsylvania Cooperative Extension Service. For more information,
contact Pennsylvania State University College of Agricultural
Sciences, Agricultural Engineering Department, 246 Agricultural
Engineering Building, University Park, PA 16802.
Dennis
J. Murphy, professor, Agricultural Engineering Department,
Cooperative Extension Service, Pennsylvania State University,
University Park, PA 16802.
|