The answer to 'why is my rat odor' is that the smell is likely caused by the presence of rats in your home. Rats have a strong, musky odor that can permeate the air and be difficult to get rid of. This odor comes from the urine, feces, and scent glands of the rats.
Some common causes of rat odor include nesting in walls, attics, or other hidden areas, as well as the decomposition of dead rats. You may also notice the odor worsening as more rats take up residence. Symptoms include a persistent, musty smell that is difficult to locate and pinpoint.