Explained: Why toxic gas builds up

. In this particular case, the silo contained chickpeas.

On Tuesday night, two men died while cleaning a grain silo, with police claiming they were knocked unconscious by toxic gas build-up inside. According to a food technology expert, Vijay Sardana, if a grain silo is not cleaned, then there is a high probability of toxic buildup of gases. In this particular case, the silo contained chickpeas.

When grain storage is left uncleaned, there is a heavy build up of moisture leading to mould growth, which leads to creation of toxins. In this case, chickpeas went through uncontrolled fermentation, and also attract microbial growth and insect infestation. Over a period of time, the insects also die, releasing a cocktail of toxic gases, Sardana said.

The toxic gases may range from hydrogen sulphide to methane, depending on the composition of the raw material. In cases of putrefaction of rice or wheat, carbon dioxide is formed; in cases of pulses, hydrogen sulphide is released. Since the gases are heavier than air, they settle at the bottom of the tank. When a worker enters the tank, he moves into an environment without oxygen. This affects brain activity, eventually affecting blood circulation in the body, said Sardana.