What makes bleach so deadly?

Bleach is hazardous because it is very reactive. Sodium hypochlorite reacts with ammonia, drain cleaners, and other acids. When toxic bleach is mixed with ammonia, toxic gases called chloramines are produced. When chlorine bleach is mixed with an acid (as can be found in some toilet bowl cleaners, glass and window cleaners, dish detergents, vinegar, and drain cleaners) chlorine gas is given off. Chlorine gas exposures, even at low levels, almost always irritate the mucous membrane and causes coughing and breathing problems, burning watery eyes, and a runny nose. Higher levels can cause chest pain, severe breathing problems, fluid in the lungs, pneumonia, and vomiting. Very high levels can cause death. Household bleach (sodium hydroxide) is not technically speaking considered corrosive or toxic, even if ingested. However, bleach exposure can cause irritation in the eyes, mouth, lungs and on skin. Individuals with asthma or other breathing problems are particularly susceptible. It can burn human tissue, internally or externally, especially in small children. The accidental swallowing of bleach is the most frequently received call at Poison Control Centers involving children under the age of six