Repellent odors, also known as 'STENCHES', are odors that are so unpleasant that they cause a feeling of disgust or revulsion. These odors can be caused by a variety of sources, such as decaying organic matter, sewage, and industrial waste. Repellent odors can be very strong and can linger in the air for long periods of time, making them difficult to ignore. In some cases, these odors can even be hazardous to health.