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					SILO GAS




           The Canada Plan Service prepares detailed plans showing how to construct modern farm buildings, livestock
           housing systems, storages and equipment for Canadian Agriculture.


           This leaflet gives the details for a farm building component or piece of farmstead xquipment. To obtain another copy of this
           leaflet, contact your local provincial agricultural engineer or extension advisor.
SILO GAS                                                              At the corner's inquest, the forensic scientist reported that the
                                                                      victims' lungs showed massive bleeding and contained high
                                                                      levels of methemoglobin, evidence of exposure to a strong
PLAN M -7410    REVISED 88:06                                         oxidizing agent. This was attributed to nitrogen dioxide (N02),
                                                                      or silo gas.

FOREWORD
                                                                      Another more recent case emphasizes that N02 is not the only
In 1977, near Gananoque, Ontario, the Conners were                    gas hazard in farm silos. In 1987, Wayne Smith, a farm
                                                                      employee of Dwight Gilmer and Sons, South Mountain,
harvesting their corn crop somewhat early because of planned
highway construction nearby. On Monday, September 12, they            Ontario, entered a tower silo. It had been lined with a
continued filling the silo but stopped on Tuesday because of          suspended plastic bag, converting the silo to an
                                                                      oxygen-limiting storage for high moisture shelled corn. Smith
rain.
                                                                      was working between the concrete wall and the slack plastic
                                                                      liner above the corn, tramping down some corn that remained
On Wednesday, September 14, they decided to resume                    around the inside perimeter of the bag after the last of the free-
harvesting. The silage distributor had not been adjusted and          flowing corn had been augered out.
silage had piled about 5 m higher against the silo wall at the
chute side. From there it sloped steeply downwards towards
                                                                      Apparently the liner ripped open at one of the seams, perhaps
the opposite side. Edward Conner (a son) apparently decided
                                                                      spilling C0 2 gas into the space where Smith was working. His
to level the silage and adjust the distributor before restarting
                                                                      body was found some time later, where he had tumbled
filling operations. Because all the chute doors were closed
                                                                      through the ripped liner and into the gas -filled space inside.
except the top one, he decided instead to go in through the roof
opening. Using a 7 m rope ladder, he let himself down the 9 m
drop.                                                                 These tragic events remind farmers and silo service people of
                                                                      the deadly nature of the gases sometimes found in and around
                                                                      farm silos. This publication explains the silo gas problem and
Jack Conner (the father) returned from town at about 11:00
                                                                      gives some safety rules for preventing further accidents of this
a.m. and noticed that Edward was missing. A hired man,
                                                                      kind.
William Carr, climbed the outside silo ladder, looked in,
shouted that something was wrong, then jumped in. He landed
part way up the silage slope.                                         RECOMMENDED PROCEDURES - A SUMMARY
                                                                      1.   POST A WARNING SIGN in an obvious place such as on
Hearing Carr's shout, Jack Conner climbed the outside ladder;              the feed room door or beside the silo chute. Many silo
he saw Edward lying at the bottom of the slope and William                 builders provide such signs, some with operating
lying part way up. Mr. Conner yelled out that the boys were in             instructions warning of gas and injury hazards peculiar to
trouble. Another brother, Eldon Conner, ran from the house                 their own brand of silo. The message can be quite simple,
and up the silo chute, followed by another hired man, Don                  such as DANGER, SILO GAS.
Littlejones. Eldon kicked in two silo doors and entered. He
tried without success to move Carr, then went farther down the        2.   Check to see if your LOCAL FIRE DEPARTMENT (or
slope to help his brother, Edward, and collapsed beside him.               similar emergency service) has the pressure demand
The father watched all of this from the top of the outside ladder!         breathing apparatus with a long air-hose for such
                                                                           emergencies. Diving gear (SCUBA) is not suitable
                                                                           because the back-pack air tank is too big to be worn while
Don Littlejones tried twice to pull Carr up to the silo chute. Jack
                                                                           climbing the silo chute or the outside ladder-cage.
went back down the outside ladder, started up the tractor and
                                                                      3.   VENTILATE THE FEED ROOM in case silo gas spills out
forage blower to ventilate the silo, then went up the chute.
                                                                           of the silo doors or is blown out by the silo unloader.
Firemen and ambulance (called by Mrs. Conner) arrived on the
scene.                                                                4.   During silo filling operations DON'T GO INTO THE SILO
                                                                           just to level the silage; instead, make adjustments to the
Then the tractor running the blower ran out of fuel. Littlejones           silage distributor at the top of the silo to keep the silage
changed tractors, but broke a shear-pin when restarting the                leveled during filling.
blower. This had to be replaced before silo ventilation could be
                                                                      5.   It is sometimes necessary to go into a silo after filling
continued. The am bulance attendant tried to climb he silot
                                                                           (such as to level and tramp the silage, install a plastic
chute with an air-pack, but it was too big for the chute and had
                                                                           cover sheet, or to setup the silo unloader). DO THIS AS
to be dropped. Without the air-pack, his rescue attempts were
                                                                           SOON AS THE LAST LOAD IS PUT IN, AND LEAVE THE
futile.
                                                                           BLOWER RUNNING while inside. Don't wait until the next
                                                                           day. When opening a chute door into the silo, climb farther
The bodies of the three men were finally removed with an                   up the chute (not down), in case silo gas spills out of the
aerial platform, from which were suspended two ladders lashed
                                                                           doorway.
together and lowered through the roof door to reach the silage
surface.
6.   Previous bulletins have recommended a safety harness           The acid content of the silage continues to increase over a
     (or at least a loop of rope under the armpits) with a rope     period of several weeks (depending on the chemistry of the
     leading to a helper at the top (the 'buddy system'). This      silage material and the air tightness of the silo). Eventually, the
     was not a bad idea, but if you fall, ONE PERSON ALONE          increasing acidity kills off the acid-forming bacteria that
     COULD NEVER PULL YOU UP THE SILO WALL and out                  produced it and inhibits the growth of molds and fungus that
     through the roof hatch or silo chute doors to safety. Two      could further damage the silage as feed. This is the normal
     helpers is the minimum!                                        silage making process which takes place in a silo with reason-
                                                                    ably airtight walls. ONE SILAGE GAS (C02) IS ALWAYS
7.   Before entering a previously-filled silo, check the depth of
                                                                    PRODUCED in this process. The period of most rapid gas
     the settled silage. To make sure that the air-blast is         production is during the first 6-7 days after filling. During this
     reaching all the way down into the headspace, attach a
                                                                    period the total volume of the various gases represents several
     tube adaptor to the blower pipe (see Figures 4 and 5).
                                                                    times the volume of the silo! For the next 3-4 weeks the gas
     Leave the chute doors closed and VENTILATE THE SILO            production tapers off. Some gases stay trapped within the
     by running the forage blower. Larger silos and deeper
                                                                    silage during the storage period and silage settlement
     headspaces require more ventilation time (see Table 1).
                                                                    continues to squeeze the gases into the headspace above
     KEEP THE BLOWER RUNNING while you are in the silo.             (see Figure 1).
8.   Once operating, the silo unloader can ventilate the silo
     quite effectively. However, if the silo unloader fails and     Another family of gases, the OXIDES OF NITROGEN (NOX),
     requires service in a recently filled silo, one must assume    can also be produced. Any weather condition, cultural practice
     that some gas may have accumulated. In this case,              or silage additive that increases the dissolved nitrate (N03)
     reventilate with the forage blower- and drop-pipe as in        content of the plant material also raises the risk of producing
     recommendation 7, above.                                       this group of deadly gases. The period of greatest danger is up
                                                                    to 3 weeks after filling.
9.   If you discover someone collapsed in the silo, the first and
     most important step is to start the forage blower and
     VENTILATE THE SILO. Providing a fresh air supply is the        For example, a drought period during the corn growing season
     most positive and immediate help to both victim and            can cause a buildup of nitrate in the soil and the corn plants.
                                                                    The corn is then harvested before the thirsty plants can
     rescuers.
                                                                    convert the nitrate into useful food proteins, and the unwanted
10. As soon as the victim is outside in the fresh air, APPLY        nitrogen is released as nitrous oxide (N20) and nitric oxide
    ARTIFICIAL RESUSCITATION, if necessary, to restore              (NO). The N20 is produced in only minor quantities and is
    breathing. Obtain medical assistance.                           relatively harmless (laughing gas, an anaesthetic), but the NO
                                                                    is another matter. This unstable NO gas can be produced in
11. Chemical gas detectors presently available are accurate
                                                                    considerable quantities and it quickly combines with any
    enough but they are not suitable for operators who do not
                                                                    oxygen remaining in the silo headspace, forming deadling N02
    also have the remote air supply equipment for silo entry.
                                                                    gas.
    Tests for C02 and NOx, should be carried out using two
    tubes for each gas. Take samples just above the lowest
    point of the silage surface.                                    Other factors that can increase the nitrate content of silage are
                                                                    nitrogen fertilizer overdose (including manure), black soils that
12. Oxygen-limiting silos are a special case. If you have to        are high in organic matter, and silage additives containing
    enter one of these silos for any reason, you must wear an       nitrate nitrogen (for increasing the protein equaivalent of cattle
    external air supply. This consists of a pressure tank, a        feed). For example, the Conners, prior to their accident, had
    supply hose long enough to reach into the silo, a               been pumping ammonium nitrate solution through the forage
    'pressure-demand' type of supply regulator and a full-face      blower while filling the silo. Urea is another nitrogen chemical
    mask.                                                           sometimes used this way.




MAKING SILAGE
                                                                    SILO GAS PROPERTIES
Fresh silage material (corn, grains, grasses or legumes), when
chopped and blown into silos, is living plant material. During      CARBON DIOXIDE (C02) is not itself damaging to health. Its
the ensiling process this living material quickly uses up the       danger lies in the factthat in silos and similar tight spaces it
limited supply of atmospheric: oxygen entrapped within the          replaces the oxygen of the air (normal air is about 21%
compressed silage mass, and dies. In this respiration process       oxygen, 79% nitrogen and 0.03% carbon dioxide). In
the oxygen is converted into some water and carbon dioxide          oxygen-limiting silos, the contained atmosphere will be almost
(C02). At the same time, acid-forming anaerobic microbes            entirely C02 and nitrogen (N2); human survival in this
multiply rapidly in the warm moist silage. They feed on part of     atmosphere depends entirely on a safe, external air supply.
the sugars and starches in the silage material and convert          Carbon dioxide is an odorless, tasteless, colorless gas that is
them to organic acids (lactic, acetic, etc.). These acid-forming    53% heavier than air. Humans and animals fortunately have a
bacteria also produce more C02.                                     built-in warning system for C02; when it reaches a certain
                                                                    concentration in the bloodstream, it triggers a nervous impulse
and the victim gasps for air. At higher concentrations this reflex       or 58% heavier), so it too accumulates at low points in the silo
action is inhibited and the victim is asphyxiated. The C02               headspace, feed room, feed alleys, etc. The threshold limit
'threshold limit value' (TLV-STEL, explained later) is 15 000            value (TLV-STEL) is set at only 5 ppm. At this level it is barely
ppm (parts per million), or 1.5% by volume.                              detectable by smell. When produced in sufficient quantities it is
                                                                         so dangerous that it can be a threat to man and beast by
In conventional top-unloading silos with roofs, C02 can                  spilling over into the silo chute and draining down into the feed
accumulate to dangerous concentrations when trapped at low               room and connecting stable.
points near the silage surface, and this risk should not be
disregarded (see Figures 1 and 2).                                       Nitrogen dioxide is deadly because when inhaled it dissolves
                                                                         with moisture on the wetted internal surfaces of the lungs,
NITROGEN DIOXIDE (N02) is a deadly gas, appearing as a                   instantly forming potent nitric acid (4N02 + 2H20 + 02 -> 4HN03).
reddish to yellowish-brown haze, with an acrid or bleach-like            Here it 'burns' the sensitive oxygen-transfer surfaces of the
odor. Like C0 2, it is heavier than air (its relative density is 1.58,   lungs, effectively stopping any further oxygen supply to the




           1   silo chute doors, closed for filling                                  1 wind blows through open roof hatch and top
           2   top of silage just after filling                                        of chute, ventilates silo dome and top of
           3   settled silage                                                          headspace
           4   dense silo gas, squeezed out of the silage,                           2 highest concentration of silo gas is at the
               remains in the headspace                                                lowest part of the headspace
                                                                                     3 workman opens chute door, silo gas pours
                                                                                       down into chute

Figure 1 Typical unsealed tower silo just after filling                   Figure 2     Behavior of silo gas on opening of a silo chute
                                                                                       door
body. Tiny blood vessels in the lungs break down, causing            Another of these pumps, made by Drager in Germany (Figure
massive bleeding, and death results (When Eldon Conner went          3), consists of a small hand-squeezed rubber bellows fitted
down the sloping silage to try to rescue his brother, his father     with check valves. One or more specified strokes of the
watched him drop unconscious almost immediately. Even if             bellows are required, depending on the concentration of the
rescue could have been completed within minutes, it is very          gas (the weaker the mix the more strokes to be counted).
unlikely that either Eldon or Edward could have been revived).       Research showed that the Drager bellows type was easier to
                                                                     use than the piston type and more suitable for the wide ranges
Even small periodic dosages of N02 (such as from working             of temperature and humidity encountered in and around farm
each day in a poorly-ventilated feed room at the bottom of the       silos. Consult the Drager chemical tube specifications and take
silo chute) has been blamed for a host of chronic respiratory        special care when interpreting the readings at temperatures
problems, including shortness of breath, coughing and fluid in       below freezing.
the lungs. These symptoms can also result from a single
non-lethal exposure and may be first noticed several weeks
afterwards. This delayed effect has sometimes made an
accurate diagnosis difficult.

DETECTING SILO GASES
During the danger period after filling the silo, use the following
silo gas indicators:
• Acrid bleach-like odor or a brownish to yellowish haze at the
  silage surface or on the feed room floor can indicate nitrogen
  dioxide. Sometimes an unnatural bright-yellow to orange
  coloration in the silage is another indicator.
• Unnatural breathing, or coughing of livestock and people,
  may indicate either N0 2 or C02, or both.
• Dead flies, cats or mice on the feed room floor, or dead birds
   in the silo, may indicate silo gases. Animals on the floor will
   be exposed to heavier gas concentrations than a standing
   person.

In addition, chemical detectors are available for many
hazardous gases, including C0 2, combined NO and N02 (NOX),          Figure 3.   Drager gas tester consisting of bellows pump,
and N02 alone. The simplest of these is a paper tape that                        attached chemical tube and extension hose for
changes color when exposed to N02 in silos and feed rooms,                       remote sampling.
but it doesn't indicate how much gas is present. The tape is
therefore not recommended.                                           A practical difficulty is that all of these chemical tube detectors
                                                                     are calibrated with the glass tubes plugged directly into their air
CHEMICAL TUBE DETECTORS, on the other hand, can be                   pumps. This means that the operator himself must enter the
calibrated and should be considered for use by trained               silo or other danger area, which is hazardous unless he is
technicians and rescue teams (firemen, etc.). This type of           wearing a remote air supply system. Use of the tube detector
detector consists of a sealed glass tube containing a specific       will give the best indication that it is safe for others to follow
chemical reagent that changes color progressively along its          without the protection of a remote air supply system. For
length when the gas in question is drawn through the tube.           practical purposes, an extension tube up to 5.5 m (18 ft) long
Each tube is activated by snapping off both ends of the glass        (provided by the manufacturer) is probably accurate enough
and plugging it into a small hand-operated air pump. Operating       when reading near the threshold limit values. At least two
instructions specify the number of pump strokes required to          chemical tubes for each gas (C02 and NOX) should be used to
draw a specified air volume through the sampling tube. The           check a silo. In many cases the extension tube is not nearly
gas concentration is read either directly or by comparing the        long enough to reach from the safety of the outside silo ladder
length of tube that has changed color to tables or charts            down to the sampling point inside the silo.
reading in parts per million (ppm), by volume.
                                                                     THRESHOLD LIMIT VALUES (TLV) are the upper safety limits
                                                                     of hazardous gas concentrations. The American Conference of
Several approved brands of tube detectors (MSA, Kitagawa,
                                                                     Government and Industrial Hygienists (1980) has published
Drager, and Gastec) are available at safety supply stores. One       two values: the TLV-TWA (time weighted average) value is the
type of air pump consists of a piston and cylinder somewhat          upper safety limit for workers repeatedly exposed for the
like an oversized hypodermic syringe. One pull of the handle
                                                                     typical 8-hour workday; the TLV STEL (short-term exposure
draws a precise quantity of the air in question (typically 100
                                                                     limit) is the upper safety limit for four daily exposures of up to
mL) through the chemical tube.
15 minutes, separated by 1-hour periods of no exposure. The           This simple adaptation improved remarkably the penetration of
latest published values for silo gases are:                           the air-blast deep into the silo headspace. The makeshift
                                 TLV-TWA      TLV-STEL                arrangement shown in Figure 2 was experimentally effective,
                              (ppm)       (%)       (ppm)    (%)      but there is too much chance that in a real gas -hazard
                                                                      situation the tube could be dislodged by air and vibration. This
Carbon dioxide (C0 2)     5000         0.5        15 000 1.5
                                                                      could leave someone in the silo without a continuing air
Nitric oxide (NO)           25                         35
                                                                      supply. Therefore the tube should be tied securely in place.__
Nitrogen dioxide (N0 2)      3                         5
Oxides of nitrogen                                                       'Spring Flex' tubing, by Flexhaust Co., 11 Chestnut St.,
(NOX)                        3*                        5*____            Amesbury, Mass., U.S.A. Available from Indus trial Rubber
* Based on the most dangerous possibility that all the NOX can
                                                                         products, 90 Commander Blvd., Agincourt, Ont. M1S 3H7,
  convert to N02
                                                                         and ForestTube Inc., 3555 boul. Cremazie E., Montreal,
                                                                         Que., H1Z 2S3.
VENTILATING THE SILO AND FEED ROOM
PORTABLE EXHAUSTER FANS were tried in controlled
experiments with C02 in full-size farm silos. Two sizes of
electric blowers were tested, each being connected to 15 m (50
ft) of clothes-drier hose.

The larger blower was rated at 215 L/s when connected to the
collapsible tubing. Once in place and operating, it reduced the
C02 concentration in the silo headspace to that of normal air
(around 3000 ppm) in 15 to 20 minutes. However, it was quite
difficult to place the tubing at the far side of the silo while
standing safely in the ladder cage outside the roof. Probably
few farmers would buy and routinely use such special-purpose
equipment.

THE FORAGE BLOWER can move more air than any other
easily-portable system, and it has the important advantage of
already being in place at the end of silo filling. Air-moving
capacities of various forage blowers running 'empty' at rated
tractor speed were from 800 to 1000 L/s (1700-2100 cfm); this
is about five times the capacity of the larger portable exhauster
that was tested! After the initial 5-8 days of most rapid gas
production, the forage blower is the most practical way to
remove silo gases.

A forage blower, equipped at the top of the silo with the side-fill
deflector-type of silage spreader (Badger, Lancaster Multi-flo,
etc.), is effective as long as the silage level is not more than 5
m (16 ft) below the distributor hood. At greater headspace
depths, however, the splitter vanes appear to break up the
airflow and prevent the air stream from penetrating deep
enough to properly mix and displace the bad air deep inside
the silo.

With the various types of rotating center-fill silage dis tributors
(Even-flo, Butler, etc.) some of the air blast is lost from the
open underside of the long arched gooseneck, and the rotating
distributor baffle-plate further deflects the remaining air-blast
toward the silo wall. With a center-fill spreader attached, the
forage blower gives rather poor ventilation, especially where
the headspace from distributor to silage is greater than 5 m.

To better direct the air-blast downward and to prevent                         1 forage blower
interference by the silage distributor (either type), a 5 m (16 ft)            2 fixed filler pipe, 230 mm (9 in.)
length of 200 mm (8 in.) wire-wound flexible exhaust ducting *                 3 200 mm (8 in.) Spring Flex wire-wound
                                                                                 tubing
was stuffed into the throat of the blower pipe (Figure 4).                     4 air blast penetrates to bottom of headspace
                                                                               5 mixed and diluted silo gas escapes through
                                                                                 open roof hatch

                                                                      Figure 4. Silo ventilation by forage blower and flexible
                                                                                drop-tube stuffed into throat of silo filler pipe
Really, a better method of attachment is required. Figure 5         opinion, we also found that the forage blower was more
shows a suggested adaptor for the rotary center fill type           effective as a silo ventilator with all the CHUTE DOORS
distributors. At this time, we are recommending to silo             CLOSED and the ROOF PANEL OPEN.
equipment manufacturers that they develop and market these
important safety devices.                                           This procedure also avoids the dangerous possibility of the silo
                                                                    gas simply moving from the silo down into the feed room and
Another important fact was discovered. Contrary to popular          connecting stable.




                1 attachment fitting and rectangular-to-round           3   external crank and cable pulls valve to
                  transition piece; bolts to throat of gooseneck,           'bypass' position for ventilating the silo
                  bolt heads smooth and flush inside throat             4   200 mm (8 in.) 'Spring Flex' wire-wound
                2 diverter flap-valve spring-loaded to 'open'               ventilaon tubing, gear clamp to transition
                   position                                                 piece 1



Figure 5. Proposed gooseneck attachment for diverting the ventilation down into the silo headspace (gooseneck
          design by Lancaster Level-Flo, Inc., Lancaster, Pennsylvania 17602, USA).
    In an emergency, black plastic drainage tubing 200 mm (8 in.)      This prevents effective natural ventilation that could be
    diameter, without perforations, could be substituted for the       accomplished by opening an outside feed room door.
    more durable and lightweight wire-wound ventilation ducting.
                                                                       A simple and inexpensive solution is to move one of the barn
                                                                       exhaust fans (the one that runs most) to the feed room. This
Table 1 gives calculated ventilation times for various sizes of        will exhaust the barn air through the feed room, instead of the
silo headspace, assuming ventilation with a forage blower at           reverse. To make sure that the heavier-than-air silo gases are
800 L/s (full rated tractor pto speed of 540 rpm) and an initial       effectively removed, build a box duct over the inside of the fan
gas concentration of 10% C02. In headspaces of 6 m (20 ft)             and extending down to about 150 mm (6 in.) from the feed
and deeper, this table is valid only with the drop pipe                room floor. The opening areas of the duct cross-section and
attachment in place. Also, this table is not applicable to the         the inlet at the floor should each be at least twice that of the
period of most rapid gas production, for 5-8 days after filling -      fan opening. The feed room should be insulated to prevent
during this extreme danger period, even the forage blower is           condensation on the walls and ceiling.
too small to assure enough gas dilution for safety.

                                                                       A further advantage of this arrangement is that in winter the
    TABLE 1    MINIMUM TIME TO VENTILATE TOWER SILO                    feed room is heated at no cost by warm air drawn from the
               HEADSPACES                                              livestock barn. It will be necessary to use some closure such
    Silo           Ventilation time* (minutes) for headspace           as a silage funnel attachment to close off the bottom of the silo
    diameter     _____________depths of________________                chute. This is to ensure that the fan will draw air from the
                                                                       stable, not from the silo. The silage funnel should be tied off
                 3m        4.5 m       6m       7.5 m       9m         with a plastic bag (or other suitable closure) except when the
    m (ft)      (10 ft)    (15 ft)    (20 ft)   (25 ft)    (30 ft)     silo unloader is operated.
    3.6 (12)       3         4          5         7          8
    4.8 (16)       5         7          9         11         13
    6.0 (20)       7         10         14        17         21
    7.2 (24)         10        14        20       25        29         REFERENCES
*   based on C-Ci = e –KQt/V                                           1.   Airborne Contaminants Committee. 1980. TLV's,
               Co-Ci                                                        threshhold limit values for chemical substances and
     where C = C02 gas concentration at time t (assumed 0.015, the          physical agents in the workroom environment, with
                TLV-STEL)                                                   intended changes for 1980. Amer. Conf. of Govt. Industrial
           Ci = inlet C02 concentration (assumed 0.0003, as in fresh        Hygienists, PO. Box 1937, Cincinnati, OH 45201, U.S.A.
                air)                                                   2.   Wells, D. 1980. Respiratory protection for agricultural
         Co = original C02 concentration (assumed 0.10 in the               tower silos and manure pits. Farm Safety Assoc. Inc., 340
                 headspace)                                                 Woodlawn Rd. W., Guelph, Ont. N1H 7K6.
          K = mixing factor (assumed 1.0)
          Q = ventilation rate (assumed 48 m³/min)                     3.   Sabourin, H.M., W.S. Reid, J.E. Turnbull and M. Ihnat.
            t = ventilation time, min                                       1982. Silo gas production, detection, ventilation and
                                                                            related safety procedurs. Can. Soc. of Agric. Eng. paper
           V = headpsace volume, m³
                                                                            no. 82-207, presented at ann. conf., Vancouver, B.C.
           e = 2.718
                                                                            Contribution no. I-421, from Eng. and Stat. Res. Center,
                                                                            Research Br., Agriculture Canada, Ottawa K1A OC6.
    THE SILO UNLOADER (once installed and operating) is an
    effective silo ventilator, but it provides no ventilation (and     4.   Turnbull, J.E. 1984. Silo gas - what can be done? Proc.,
    hence no protection) before it is lowered to the leveled silage         Int. Silo Safety Conf., Kitchener, Ont. Nov. 28.
    surface, adjusted and started up. This start-up time is,                Contribution no. I-660, from Eng. and Stat. Res. Center,
    unfortunately, the time of greatest risk from silo gas.                 Research Br., Agriculture Canada, Ottawa K1A OC6.
                                                                       5.   Meiering, A.G., M.G. Courtin, S.F Spoelstra, G. Pahlow,
    FEED ROOM VENTILATION is important as well. There is a
                                                                            H. Honig, R.E. Subden and E. Zimmer. 1988.
    real danger that silo gas can fill up to the level of the open
                                                                            Fermentation kinetics and toxic gas production of silages.
    chute doors and spill down the silo chute. This is of little
                                                                            Trans. of ASAE. Vol. 31.
    consequence if the silo stands alone outside and is connected
    to the feed room with only a feed conveyer. In most cases,
    however, the silo chute connects directly through the roof of an
    attached feed room, and the feed room connects in turn with
    the barn. Exhaust ventilation fans in the barn can easily draw
    silo gases through the crack under the feed room door,
    endangering livestock as well as people. The problem is
    potentially worse where the feed room floor is below outside
    ground level (a common situation with bank barns).

				
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