Canadian Grain Commission
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Spoilage and heating of stored agricultural products

Chapter 8 – Problem investigation

This chapter provides guidelines for persons investigating the causes of spoilage problems that result in animal sickness and death, and the causes of heating problems that result in fires or explosions. The investigation of these types of problems requires a careful systematic approach, making the fullest possible use of available information. The collection and documentation of such information is of paramount importance if legal proceedings are later involved (see Chapter 9).

For an excellent account of the damage that can be caused to commodities during storage, stowage, and carriage, the reader is referred to Knight (1985).

Spoilage and/or animal sickness

Suggested steps to take when investigating spoilage and/or animal sickness problems, as summarized in Table 11, are as follows:

Information collection

Visit the site promptly. Interview key persons involved, such as eye witnesses. Take photographs of premises and of sick or dead animals.

Extent or spoilage

Ascertain the source of the spoiled and sickness-associated materials. For instance, were the materials produced, stored, and used as feed on the premises or were they manufactured elsewhere and brought to the site to be stored and used as feed, for example feed pellets? Determine whether the spoiled or suspect materials formed a portion or all of one or more bins on site. If confined to one bin, determine the location of the affected material. This might be in the upper or lower part of the structure, in pockets, near the upper centre, near doors, near the aeration floor, under spout lines, on the surface, or close to or adherent to walls. Take samples of affected and unaffected stocks for comparison purposes, using a scoop, multi-chambered trier and/or deep bin probe, label them, seal them in double plastic bags, and place in a cooled container for transportation to the laboratory. Take photographs of the affected and unaffected sampled material.

Cause or spoilage

Spoiled material that occurs in the upper part of the bin is sometimes caused by extra moisture entering or becoming localized in the region. Spoilage is also caused by rain or snow entering through open or poorly sealed hatches, or via improperly sealed joints between sheeting or bolt holes. Other causes include the entrance of run-off water from elevator buckets or grain spouts, the development of moisture migration in non-aerated bins, the development of a moisture front in aerated bins through inadequate fan size or interruption of aeration, the presence of excessive green weed seeds, or the accumulation of fines under the spout lines as a result of a spreader either not being used or not being used properly. Spoiled material that occurs in the lower part of the bin is often caused by extra moisture entering via a leak between the concrete floor and bin wall or via a poorly sealed door. Higher moisture material may occur in spring in the dead spots near the walls above the partially perforated aeration floor. If spoilage in the bin is not confined to one area, then some or all of the seeds were binned at too high a seed moisture content, and possibly seed temperature, for safe storage.

Animal sickness

In situations involving animal sickness, change existing feed and use feed from a fresh source to alleviate symptoms and to either implicate or exonerate the original feed. The following actions may then be considered: ascertain the history of the flock or herd and its normal sickness rate; obtain history of current feed to determine whether sickness symptoms were associated with an old consignment or with a new one; obtain information on the reliability of the supplier and any problems that might have been encountered by other customers; discuss animal sickness and stress symptoms with a veterinarian; attend postmortem examinations, if possible, and take photographs; look for possible source of spoiled feed, for example water or rain leaking into feed troughs, presence of hard lumps of material in the feed, or use of moldy grains that could be associated with toxins; take samples of affected and unaffected materials as checks, identify them, and photograph them.

Analysis of samples

Examine all suspect and control samples for increased moisture content levels, decreased seed germination levels, increased fat acidity value levels, the presence of musty or off odors, and the presence of species of preharvest and/or post-harvest molds. Where animal sickness is involved, analyze samples for aflatoxins, ochratoxin A, sterigmatocystin, citrinin, patulin, penicillic acid, trichothecenes, zearalenone, and other mycotoxins, depending on the preharvest and/or post-harvest molds present in the sample and the symptoms of animal sickness. Analyze feed ingredients of manufactured feeds to determine whether duplicate or even triplicate dosages of particular items were accidentally added.

Advice on control and prevention

Once the cause of spoilage has been determined, take steps to control the situation and prevent its reoccurrence. Remove and discard spoiled material, wash down or spray walls with a solution containing two parts Clorox® and eight parts water to control spoilage molds (Charles 1985), then if necessary dry the unspoiled remainder and rebin. As a preventive measure, seal bins and install proper aeration and monitoring devices.

With instances of animal sickness, change the feed or the supplier of feed and order quantities sufficient only for short-term use.


During the investigation remember that spoilage is most often caused by improper storage of the material. There are many reasons for improper storage: the moisture content and temperature of the material at binning might have been initially too high for safe storage and needed to be dried or aerated, the material might have been improperly aerated or improperly treated with propionic acid during the storage period, or perhaps moisture was allowed to locally increase during storage either due to moisture migration or through leaky roofs and walls. Animal sickness symptoms may be associated with the presence of mycotoxins or with mistakes in feed ingredient dosages. They may also be associated with numerous other agents or factors. The assistance of an experienced veterinarian familiar with sickness patterns in the type of animal is essential to determine the exact cause of the sickness.

Table 11 – Suggested steps for investigation of spoilage and animal sickness problems in stored commodities
Suggested steps
1) Information collection
  • Get to site as soon as possible
  • Interview key persons
  • Take photographs of premises, sick animals
2) Extent of spoilage
  • Ascertain whether source of spoiled and sickness-associated materials is on site or derived from outside
  • Determine whether affected materials form a portion or all of bin(s) on site
  • If affected materials form a portion of bin(s), determine its location within the bin(s)
  • Take samples of affected and unaffected materials, then label, bag, and later photograph them
3) Cause of spoilage
  • If spoilage occurred in the upper part of the bin, look for badly fitting hatches, missing bolts, water in bucket elevator, moisture migration, aeration problems, non-use of spreader
  • If spoilage occurred in lower part, look for leak between bin wall and concrete wall, poorly fitting doors; spoilage in dead spot above aeration floor
  • If general spoilage occurred, probably the product moisture content was too high for safe storage
4) Animal sickness
  • Check out infectious disease(s) as cause
  • Change to new feed
  • Check history of herd/flock
  • Check history of feed, determine whether new consignment was involved
  • Check history of supply, determine whether new supplier was involved
  • Consult a veterinarian, obtain post-mortem results
  • Look for source of moldy material
  • Take samples of affected and unaffected materials, then label, bag, and later photograph them
5) Analysis of samples
  • Check for increased moisture content levels, increased FAV (fatty acid values)
  • Check for decreased seed germination
  • Examine for musty or off-odors
  • Check for preharvest and post-harvest molds
  • Check for mycotoxins
  • Check feed ingredients and dosages
6) Advice on control and prevention
  • Spoilage: remove and discard affected material, dry remainder and rebin, seal bins, aerate
  • Animal sickness: change feed, change supplier, order short-term supplies
7) Summary
  • Spoilage is most often caused by improper storage
  • Animal sickness is caused by mycotoxins in the feeds, by mistakes made during feed formulation, or by many other agents and factors
  • Consult a veterinarian who is familiar with sickness patterns in the animals affected regarding the probable cause of sickness

Heating, fires, and explosions

These types of problems can vary from being of relatively minor importance, involving localized pockets of heated material within a bulk, to being of major importance, involving destruction of storage facilities and damage to stored commodities by fire and/or explosion. Suggested steps to take when investigating heating and fire- and explosion-related problems, as summarized in Table 12, constitute a checklist of the major points to be considered in most investigations. Due to the complex nature and uniqueness of problems, the list does not cover all eventualities.

Information collection

Visit the site promptly. Interview on- and off-duty staff, insurance adjusters, firefighters, police officers, newspaper reporters, and eye witnesses regarding the source of the heating, fire, or explosion. Obtain photographs and samples before excessive site disturbance occurs.

Extent of problem

Ascertain the nature, type, and volume of the commodity or commodities involved; the extent of the damage caused to the facilities and stocks; the structural condition of the facilities and existence of hazards; and the fire-fighting procedures used.

Cause of heating

Examine temperature, moisture content, and product condition records to determine whether pockets of high moisture material existed as a source of heating in the stocks. Such records and interviews with personnel permit an assessment of the frequency and adequacy of cleaning, aerating, turning, and insect monitoring and control procedures used in the facility. The undetected entrance of rain or snow via leaks or of water via bucket elevators, the use of defective or poorly calibrated moisture meters, proximity to steam pipes, engine spaces, or illuminated electrical lights, and improper use of fumigants are all potential causes of heating problems and should be checked.

Cause of fire and/or explosion

Fires may be caused deliberately for reasons such as financial gain, to conceal another crime, to destroy or protest, to become a hero or heroine, to fulfill a need (mental disorder), or because of boredom (Dennett 1980). Generally, because of prior involvement, the presence and activities of arsonists in a community are known to the police. Clues such as remnants of oily rags may provide evidence of arsonists activities.

Fires and, in particular, explosions, may result from the use of welding equipment in and around storage facilities. The sparks provide a primary ignition source for an initial dust explosion, which dislodges debris from ledges and provides the fuel for a subsequent major conflagration.

Overheated mechanical bearings and electrical motors, and faults in electrical fittings and wiring are also known to cause fires (see Fig. 6). Because lightning can set fire to structures it is worthwhile to check for damage to the lightning conductor and for the occurrence of electrical storms at the time of the fire.

Static electricity can cause explosions in dusty situations; therefore check the procedures used for minimizing risk from electrostatic charges in the facility. Overalls made of synthetic materials with a high capacity for retaining electrostatic charges can be instrumental in causing an explosion.

Fumigants containing either aluminum or magnesium phosphide are often used in pellet or strip form to control insects in flour mills and other bulk storage areas. When exposed to moisture or heat these substances produce the flammable toxic gas phosphine. For this reason, the investigator should check with plant personnel to determine whether fumigation with these substances had recently occurred. Fire may result from the accidental addition of water to fumigant pellets or strips or even from rain coming into contact with the contents of discarded fumigant containers dumped into the garbage. Localized high concentrations of pellets poorly distributed within a mass of grain can create enough heat to cause a fire or to damage the kernels of grain immediately above, resulting in downgrading and economic loss. Ventilation by fans in premises fumigated with phosphine may result in ignition due to changes in gas compression and sparks from the fans.

Fires and explosions may result from the self-ignition of strongly heating commodities exposed to air or oxygen. An indication of self-heating or self-ignition on site is the presence of very hot fused material within otherwise cool stocks, some of which may have ignited when exposed to air and provided an ignition source for dust explosions. The fused lumps may have originated from within a ship, barge, railcar, or silo and may have been carried via conveyor belts for some distance within the plant to the site of the fire or explosion. Another indication of self-heating is the presence of brown liquids coming out of bin seams, and sooty deposits beneath aeration floors, both the result of improper aeration of strongly heating stocks. Often, strongly heating stocks will continue to smolder for long periods but will not ignite unless additional air or oxygen is supplied.

Fires and explosions may result from complex causes; see an interesting account of the SS Green Hill Park disaster by Stanton (1987).

Examination of facilities

Obtain a floor plan of the facility that shows the location and contents of each storage bin, ship, barge, truck, or railcar. Determine whether any movement of stocks was occurring at the time of the fire or explosion, and if so, the type of commodity and the locations involved. Examine the facility and its contents for evidence of the causes (see Table 12, section 3b). If possible, do this while uncovering the stocks with an experienced salvage operator. Look, for example, for remnants of oil-soaked rags as evidence of arson, and for the presence of discarded fumigant containers as a possible cause of the fire or explosion. Determine the location of the initial heat source and probable path of fire and explosion from on-site examination and photographs. Obtain samples of unaffected, heat-damaged and fire-damaged material, then label and photograph the samples and put them into bags.

Analysis of samples

On laboratory receipt, examine the samples, divide them into spoiled, bin-burnt, and fire-burnt categories, and relate their occurrence to sites of spoilage, heating, fire, and/or explosions in the plant. The presence of fused heated material may indicate a source of self-heating or it may relate to damage caused much later when the stored material was consumed by fire.


Heating problems in stored commodities are most likely caused through biological and chemical activity. Fires and explosions are not usually caused by self-heating; therefore other causes, for example, arson, should first be examined. Self-ignition may be involved if heated fused material is exposed to air or is aerated. Fires and explosions may result if heated fused material is transported into a facility after unloading silos, railcars, ships, or trucks.

Table 12 – Suggested steps for investigation of heating, and fire and explosion-related problems in stored commodities
1) Information collection
  • Get to site as soon as possible
  • Interview key persons and eyewitnesses on origin of the problem
  • Check local newspapers for photographs, and reports
  • Take own photographs
2) Extent of problem
  • Determine the type and volume of commodities involved
  • Determine the damage caused to facilities and stocks
  • Ascertain age of facilities and type of construction
  • Check structural condition of the facilities
  • Check for possible fire hazards
  • Determine what fire fighting and other procedures were used
3a) Cause of heating
  • Storage of high moisture content material
  • Improper or inadequate storage management procedures, including cleaning, aerating, turning, monitoring and insect control
  • Entrance of moisture through leaks or bucket elevator
  • Defective, poorly calibrated moisture meters
  • Proximity to steam pipes or other heat sources
  • Improper use of fumigants
3b) Cause of fire and/or explosion
  • Arson
  • Welding
  • Mechanical
  • Electrical
  • Lightning
  • Static electricity
  • Improper fumigant use
  • Self-ignition, lumps of very hot material within stocks or in railcars or ships
  • Explosion, addition of water or foam to fire in silo
4) Examination of facilities
  • Obtain floor plan of facility, showing location and contents of each storage bin
  • Examine structure and contents for evidence of causes listed in section 3b of this table
  • Determine location of initial heat source, path of fire, or explosion
  • Look for used fumigant containers
  • Obtain samples of unaffected and affected material, then label, bag, and photograph them
5) Analysis of samples
  • Differentiate between spoiled, bin-burnt, and fire-burnt material
  • Relate these to sites of spoilage, heating, fire, or explosion
  • Examine lumps of black fused material and relate to either self-ignition or late fire damage
6) Summary
  • Heating problems are usually caused by biological and chemical activity
  • Self-ignition is the least likely cause of fires and explosions; therefore check for other causes such as arson first
  • Self-ignition might be involved if heated material is aerated or exposed to air
  • Explosions may result if heated fused material is transported into a facility from a railcar, barge, or truck