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Silo Gas Alert


There is increased potential for high nitrates and therefore silo gas (nitrogen dioxide) in recently harvested corn silage due to the dry growing season this year. Farmers exposed to silo gas are at risk of severe respiratory distress, permanent damage to lungs, and even sudden death.

Reports of silo gas are coming in. Some of the corn in these silos did not appear to be severely stressed in the field. Precautions should always be taken in tower silo situations.

Silo gas is produced almost immediately after filling a silo. The greatest risk is the first 12 to 60 hours after filling the silo, and then risk declines for approximately 4 – 6 weeks when silage fermentation is complete. Silo gas has a bleach-like odour and may be visible as a reddish-brown haze. However, it is not always visible.

Nitrogen dioxide is heavier than air, therefore it tends to be located just above the silage surface. It may flow down silo chutes and into feed rooms. Tower silos are at greater risk because the silo gas is contained at the silage surface level, and operators often enter the silo after filling to level silage and set up the unloader.

When inhaled, nitrogen dioxide mixes with body moisture to form nitric acid which causes severe burning of the lungs and the rest of the respiratory system. Pulmonary edema results. Victims often collapse. Other people attempting a rescue can also be overcome. Farmers exposed to silo gas should get immediate medical attention. Do not enter a silo during the risk period without wearing an appropriate self-contained breathing apparatus. Before entering the silo, ventilate it by running the forage blower for 30 minutes and leave it running while inside. Also ventilate the silo room and chute. Post appropriate warning signs, and keep people and animals away.

For more information on preventing injury or death from silo gas, refer to:

• Silo Gas Dangers - Workplace Safety and Prevention Services



• Silo Safety - Workplace Safety and Prevention Services

• Hazardous Gases - OMAFRA Factsheet 04-087

• Farmers with concerns about silo gas should contact the Workplace Safety and Prevention Services, (formerly the Ontario Farm Safety Association) at 1-877-494-9777.



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