Never mix Hydrochloric acid with Sodium hypochlorite (chlorine bleach)
Toxic gas
Chlorine gas is released, and this is the strongest domestic version of the acid-and-bleach reaction because hydrochloric acid is the strongest acid a householder is likely to have. Chlorine causes coughing, chest tightness and shortness of breath, and its effects can be delayed by hours. Get well clear, do not go back in to ventilate, and seek medical advice even if breathing settles.
Precautions
- Never mix with other cleaning products
- Ventilate the area
- Wear gloves
- Wear eye protection
- Keep away from children and pets
- Consider professional help
- Dispose of responsibly
How this happens
The regulator states it from the acid's own side: hydrogen chloride reacts with oxidising agents — its list names chlorine, chlorates, nitrates, peroxides and permanganates — to form toxic chlorine gas. Sodium hypochlorite is an oxidising agent and a chlorine source, so the reaction is fast and needs no heating. The domestic setting is an outdoor one: brick acid is used on mortar smears, patios and hard landscaping, and a chlorine-based product is used on the same surfaces for algae and moss, often in the same afternoon.
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
- Hydrochloric acid — The strong mineral acid in brick acid and the harshest toilet cleaners. It attacks copper, brass and zinc, and meeting an oxidiser it gives off chlorine gas.
- 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.
Evidence
Strongly supported
Sources
Right to Know Hazardous Substance Fact Sheet: Hydrogen Chloride (RTK 1012)
New Jersey Department of Health, 2016 · Government or regulator
Relied on for: That hydrogen chloride reacts with oxidising agents such as perchlorates, peroxides, permanganates, chlorates, nitrates, chlorine, bromine and fluorine to form toxic chlorine gas. (states this directly)
Right to Know Hazardous Substance Fact Sheet: Chlorine
New Jersey Department of Health · Government or regulator
Relied on for: That chlorine is a severe respiratory irritant, that it is a strong oxidiser, and that overexposure requires medical attention. (states this directly)
Dangers of Mixing Bleach with Cleaners
Washington State Department of Health · Government or regulator
Relied on for: That bleach must not be mixed with acidic products because toxic chlorine gas is produced. (states this directly)