As long as silage remains a common livestock feed, the risk of an injury or fatality from silo gases is present. Every farm worker must understand the dangers associated with silo gases and how to deal with them.

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, oxygen limiting, 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. However, this odorless and colorless gas is very dangerous because the gas displaces the silo's oxygen, and in high concentrations, gives a person little warning that they are 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 can be formed in conventional silos but generally, nitrogen dioxide is the most prevalent type of gas. This highly toxic gas is characterized by a strong bleach-like odor and, under certain conditions, can be visible as a fog from a distance (sometimes mistaken for smoke). If the gas is highly concentrated, this fog will appear to be yellow to reddish brown in color and the silage surface, silo wall, base of the chute and other structures of the silo may be stained (yellow, orange, reddish) from the gas.

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 three 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.

To learn more about the dangers of silo gases and how to deal with them, read the article “Silo Gases — the Hidden Danger” on Cover Crop Strategies.