Why do you get bad smell while burning animal fiber?

Burning animal fibers, such as wool or silk, produces a bad smell primarily due to the presence of proteins like keratin. When heated, these proteins break down and release volatile compounds, including sulfur and ammonia, which contribute to the unpleasant odor. Additionally, the high nitrogen content in animal fibers can also produce pungent gases when burned. This contrasts with burning plant fibers, which typically emit a more neutral scent.