Why does paint smell bad over time?

Paint can develop an unpleasant smell over time due to the breakdown of volatile organic compounds (VOCs) and other chemicals in the paint as they evaporate. As these compounds oxidize or react with air, they can produce foul-smelling byproducts. Additionally, mold or mildew growth can occur in improperly stored or applied paint, contributing to a musty odor. Lastly, the degradation of paint materials can also lead to a change in smell as the paint ages.