What should never be mixed with bleach (sodium hypochlorite)?

Mixing bleach (sodium hypochlorite) with ammonia produces toxic chloramine gases, which can cause respiratory problems and other serious health issues. Chloramine gas is particularly hazardous, as it can irritate the eyes, skin, and respiratory tract, and in high concentrations, it can be life-threatening.

Additionally, while mixing bleach with vinegar creates a chemical reaction that produces toxic chlorine gas, which is also hazardous, the focus in this context is on the most dangerous combination. Ammonia poses a significant risk because it's commonly found in various household cleaners.

Water and soda do not create harmful reactions with bleach and are safe to mix, though the effectiveness of bleach may be reduced when diluted with water. The primary concern with chemical safety is understanding the nature of reactions that generate toxic gases, and ammonia's interaction with bleach is among the most crucial to avoid.