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Canola binned hot, even if it has low moisture, low dockage and low green, should still be put on aeration. This will even out the temperature throughout the bin and help remove moisture from respiring seed. Even at low moisture, convection currents within the bin could concentrate this moisture. For safe, long-term storage, canola should be conditioned with aeration to less than 8% moisture and cooled to 15°C or less.
Moisture, dockage and green add to the risk.
High-moisture pockets. Even if most loads are very dry, adding just one or two late-day loads with high moisture could be a start point for heating. This moisture creates a more hospitable environment for microbes (mostly moulds) that trigger heating. Read more in the Canola Encyclopedia.
Green canola. Green canola seeds can increase the storage risk, even if canola is dry and cool. Monitor closely. Small shrivelled canola seed, which often occurs in combination with high-green seed, can mean smaller air pockets between seeds in the bin. This can increase the resistance to air flow.
Weed seeds. Weed seeds tend to contain more moisture than canola seeds, especially if they are green or immature. These high-moisture seeds may not be enough to elevate overall grain moisture tests, but if these weed seeds congregate in pockets in the bin they can create localized hot spot for spoilage to begin — especially if that canola is also binned hot. Bits of green weed material in the sample increase the risk.
Chaff. Without a spreader in the bin, chaff tends to concentrate closer to the walls of the bin and fines closer to the centre of the bin. This distribution exaggerates airflow problems because air tends to take the path of least resistance. Concentrated areas of chaff, which could be a start point for spoilage, may be a more serious issue in larger bins. Straight-combined canola may have higher percentage of still-green chaff, which could further increase the storage risk.
More on microbes from the Grains Canada Guide:
The various types of spoilage fungi each require a different relative humidity level and temperature for their growth and development. Some species, like Aspergillus amstelodami (a yellow-green mold sometimes found growing on the top of homemade jams), grow at low humidities…and produce water during their growth, which enable more damaging molds to grow.
Further reading:
