Synthetic dyes will stain the white material, while the smell of chlorine means that the carpet has been bleached to make it look older.
If a carpet smells of chlorine, it is safe to assume that it is not as old as it appears to be. 
mnli hypothesis: If a carpet smells of chlorine, it is safe to assume that it is not as old as it appears to be.  premise: Synthetic dyes will stain the white material, while the smell of chlorine means that the carpet has been bleached to make it look older.