A pervasive and persistent odor around your home can be very frustrating when you do not know where it comes from, especially if a deep clean and thorough airing of your home does not remove it. The nature of the smell in your basement or wider home can even help you to figure out what the most likely cause is (and the concentration of the smell can help you to pinpoint hotspots). If the smell in your home is largely musty in nature, then it is most likely being caused by dampness and the formation of fungi like mold and wood rot. This smell is likely to get worse when you are in close proximity with large formations, and may also cause symptoms similar to those caused by hay fever and other mild allergies. You will recognize mold and fungal growths in your home primarily by discoloration and changes in the texture of affected organic materials like wood or textiles. If the smell has a more vinegary edge, however, then it is most likely to be a form of pest infestation. Most specifically, vinegary smells are associated with cockroach infestations. If, however, the odor in your home smells of ammonia, then it is more likely to be the result of a rodent infestation in your home. If the cause of the unpleasant smell in your home is infestation, you are likely to see other signs. For example, you may see things like droppings, nest formations, and of course, the pests themselves.