Silo gas is the common name for nitrogen dioxide.  It is a yellowish-brown or reddish-brown gas that has a pungent, acrid odor.  It can be found in diesel fuel when burned, or in silos containing corn silage.  Signs and symptoms include:

• At 5-10 ppm, eye and throat irriatation.
• At 20 ppm, eye irritation.
• At 50 ppm and above, tightness in the chest, acute bronchitis, and death from prolonged exposure.

Continuous air monitoring with monitor that detects nitrogen dioxide and ventilation are the best means of prevention, in addition to avoiding exposure during the initial phases of corn silage fermentation, which can last up to 2 weeks after filling the silo.