Because carpet is made up of countless tiny fibers, it’s completely normal for it to hang on to odors. Just like clothes, blankets, and other fibrous items, your carpet will begin to retain odor over time, especially if it hasn’t been deep-cleaned consistently.
Carpet also has an underlay — a base layer of padding that isn’t directly exposed to the air. Because it’s hidden, it holds onto odors and can be difficult to clean.