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Never mix Sodium hypochlorite (chlorine bleach) with Ammonia

Toxic gas

Chloramine gases are released. These are severe respiratory irritants: exposure causes coughing, shortness of breath, chest pain, wheezing, nausea, watery eyes and irritation of the throat, nose and eyes, and in serious cases pneumonia and fluid in the lungs. In an enclosed space such as a bathroom, concentrations build quickly. Get into fresh air at once and seek medical advice. FEELING BETTER SHORTLY AFTERWARDS IS NOT AN ALL-CLEAR: the regulator recommends medical observation for 24 to 48 hours after overexposure, because fluid on the lungs can be delayed.

Precautions

  • Never mix with other cleaning products
  • Ventilate the area
  • Keep away from children and pets
  • Consider professional help

How this happens

Sodium hypochlorite reacts with ammonia to form chloramines, which are volatile and escape into the air as gas. The reaction requires no heating and no unusual conditions. The danger lies in everyday circumstances: ammonia is present in some glass and multi-surface cleaners without being prominent on the label, and it is present in urine, so the reaction commonly happens when bleach is used on a toilet, a litter tray or a pet accident rather than when somebody deliberately combines two bottles.

If it has already happened

Get everyone into fresh air straight away, and do not go back inside to open windows. Anyone with breathing difficulty, chest pain, persistent coughing, or a chemical splash to the eyes needs medical attention — treat it as an emergency and call your local emergency number. In the United Kingdom, use NHS 111 or 999 as appropriate; clinicians can consult the National Poisons Information Service.

The substances involved

  • Sodium hypochlorite (chlorine bleach) — A powerful oxidising bleach and disinfectant. It is also the substance behind the most common serious household chemical accidents, and must never be mixed with anything.
  • Ammonia — An alkaline cleaner found in some glass and general-purpose products. What matters most about it is what it does when mixed with bleach.

Evidence

Strongly supported

Sources

  1. Dangers of Mixing Bleach with Cleaners

    Washington State Department of Health · Government or regulator

    Relied on for: That mixing bleach with ammonia produces toxic chloramine gases, and the specific health effects listed including pneumonia and fluid in the lungs. (states this directly)

  2. Hazard Alert — Worker Health and Safety: Mixing Bleach with Other Cleaning Products Can Be Deadly

    New Jersey Department of Health, Environmental and Occupational Health Surveillance Program · Government or regulator

    Relied on for: That mixing bleach with ammonia creates chloramine gases with the effects described, and that ammonia-containing products are among those not to be combined with bleach. (states this directly)

  3. NIOSH Pocket Guide to Chemical Hazards

    US National Institute for Occupational Safety and Health (NIOSH), CDC · Poison or chemical-safety authority

    Relied on for: That chloramine and chlorine are recognised hazardous respiratory irritants with established occupational exposure limits. (background and mechanism only)

  4. Right to Know Hazardous Substance Fact Sheet: Sodium Hypochlorite

    New Jersey Department of Health · Government or regulator

    Relied on for: That medical observation is recommended for 24 to 48 hours after overexposure to sodium hypochlorite, as pulmonary edema may be delayed. (states this directly)

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