A self-contained breathing apparatus is needed for silo entry when toxic gases are present.

Now is the time to understand the dangers of silo gases.

Silo gases form through the fermentation of chopped forage shortly after forage enters the silo. Levels peak about three days after harvesting and then quickly decrease, especially if the silo is ventilated.

Dennis Murphy, Penn State professor emeritus of agricultural engineering, recommends not entering the silo during those three days after ensiling.

However, he notes there are times where entry into conventional (non-sealed) silos may be needed. For example, loaders break down, chute covers must be put on, silage must be leveled, and filling the silo is usually not done in one cutting.

The most abundant toxic gas formed in conventional silos is nitrogen dioxide. It smells like bleach and can look like fog at a distance. You could mistake it for smoke.

The fog will appear to be yellow to reddish brown when the gas is highly concentrated, and the silage surface, silo wall, base of the chute and other silo structures may stain yellow, orange or reddish from it.

Nitrogen dioxide causes severe irritation to the nose and throat and may lead to swelling of the lungs. Extremely high concentrations of gas will cause instant distress, collapse and death within minutes.

Milder concentrations could cause upper respiratory congestion, watery eyes, cough, difficulty breathing, fatigue and nausea.

This gas is especially dangerous because low-level exposure causes only a little immediate pain or discomfort. Feeling just mild symptoms, you might stay in the area to finish the job, making the effects of silo gas worse.

Effects can last for hours in the body, causing symptoms to become worse and worse over a day or two.

If you experience any of these symptoms when inside or near a freshly filled silo, you should stop your task and immediately exit to fresh air.

Immediately go to your doctor or hospital emergency room and report that you have been exposed to “silo gas poisoning.”

One after-effect of silo gas poisoning is fluid in the lungs leading to chemical pneumonia and possibly death if not treated right away. The effects of fluid filling the lungs may not show up until several hours after the exposure, which may be too late.

Nitrogen dioxide is heavier than air, so the highest concentration of gas is usually located at the silage surface — your entry point if you need to enter the silo for any reason.

If a silo door is open near the surface of the silage, the high concentration of gas could exit the silo through this door, and flow down the chute. This could cause it to settle at the base of the silo or in the feed room, or even flow into the barn area.

To prevent silo gases from poisoning your livestock, provide good ventilation wherever possible in and around the silo when silage is fermenting. Also, make sure to close the door between the feed room and the barn.

Please, clearly communicate the seriousness of this hazard to each family member, especially children. Keep them away from areas where they could be exposed to silo gas.

A self-contained breathing apparatus is needed for silo entry when toxic gases are present.

Stay out of the silo during the first three days after filling. If you must enter the silo after the first few days, these tips will reduce your risk of silo gas exposure:

1. Ventilate the silo and all nearby areas thoroughly before entering. Open upper chute doors down to the level of the settled silage and run the silo blower for 15 to 20 minutes before going into the silo. Keep the blower running for the entire time you’re in the silo.

2. Never enter a silo unless another person is present and could go for help in an emergency.

3. If it is necessary to enter a silo containing silage, the person entering must wear a self-contained breathing apparatus and a harness attached to a lifeline and secure anchor point. Dust masks and chemical cartridge respirators will not provide protection.

4. Post signage reading “Danger — Deadly Silo Gas” around the base of the silo warning people to stay away.

5. Lock out and tag out the power supply for all unloading mechanisms before entering any silo, at any time

Occasionally, neighbors mistake excessive silo gas for a fire. If the fire company is called, make sure firefighters use a thermal-imaging camera to identify any excessive heating of the silo, or temperatures more than 190 degrees.

Heidi Reed is a Penn State Extension educator in York County.

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