Because ammonia reacts with bleach to produce toxic fumes, inhaling the vapors that come off this mixture will likely lead to poisoning and a serious health emergency. The effects of inhaling high concentrations of bleach-and-ammonia vapors are described by Reference.com as severe.
When bleach and ammonia mix, their reaction generates a laundry list of additional compounds, nearly all of which are toxic. According to About.com, these chemical reactions include hydrochloric acid, chlorine gas and hydrazine. Chlorine gas is so toxic that it was used as a weapon during World War I. Hydrazine is volatile and can even explode if present in sufficient concentrations. Hydrochloric acid is a powerful acid that can easily cause serious chemical burns on exposed tissues such as the trachea, esophagus and lungs.
Anyone who has been exposed to these chemicals should seek medical treatment right away, especially if the chemicals are inhaled. The National Institutes of Health reports that how well a patient ultimately responds to medical treatment largely depends on how quickly the chemicals present in the body can be neutralized or diluted. Anyone who is near to a release of these fumes should leave the area and call the local poison control hotline for advice.