Mixing produces a toxic gas

When bleach is mixed with ammonia, toxic gases called chloramines are produced. Exposure to chloramine gases can cause the following symptoms:

• Coughing.
• Nausea.
• Shortness of breath.
• Watery eyes.
• Chest pain.
• Irritation to the throat, nose, and eyes.
• Wheezing.
• Pneumonia and fluid in the lungs.

https://doh.wa.gov/community-and-environment/contaminants/bleach-mixing-dangers