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What is the toxic effects of mixing muriatic acid and chlorine?


Q. At my friend's school, the janitor mistakenly mixed muriatic acidamazoninfo with chlorine. Actually he poured this muriatic acid into the swimming pool by mistake. The fumes were very bad and after the students arrived at school, they were sent home. The teachers, were asked to stay. The fumes were so strong, it was making students as well as teachers sick. So what I'm asking is, what side effects could occur by ingesting this mixture? And, would this combination of chemicals be toxic.

Valda Lofton
- Ann Arbor, Michigan


A. Adding muriatic acid to a pool is common. Something is not being told. Normal-reasonable additions will not cause the problem if the acid was added to the pool water. Now if it was added to the system in a manner that got to a chlorine tablet chlorinator, you could have a significant problem. My guess is that you use chlorine gas and a gross excess was added and more probably there was a chlorine leak or a boo-boo. Realize that this is speculation on the cause based on extremely limited information.

James Watts
- Navarre, Florida


A. Hi, Valda. We metal finishers might be able to help with the side effects on the pool and building, but the question of side effects of this dangerous reaction on people is for doctors to tell you :-)

As Mr. Watts says, any analysis of the incident from this distance is speculation. But people can and do confuse bleach (sodium hypochlorite) with hydrochloric acid and mixing them will generate chlorine gas and other nasty gasses.

I read of a major evacuation of a whole neighborhood when a tank truck driver asked a plating shop manager where "to pump the [mumble] hypochlorite" and the shop manager said "pump the [mumble] hydrochloric" into "this tank here", resulting in mixing the two in large volume. A good reason for us to not abbreviate or use slang when speaking of calcium hypochlorite and hydrochloric acid :-(

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Ted Mooney, P.E. RET
Pine Beach, New Jersey

Effects of Exposure to Toxic Gases

In the Mouth of the Dragon: Toxic Fires in the Age of Plastics


A. I re-read your question. First, to most of us, ingestion means eating or drinking it. If it is a gas, it would be inhalation. Second, toxic is in the dose- a basic definition of toxicology. What was the product/byproduct of the event is anyone's guess because we do not know all of the items that were involved in the reaction. An approximate-very approximate effect on the body would be to look up the MSDS for chlorine gas. Realize fully that there were probably trace amounts of other gasses.

James Watts
- Navarre, Florida


A. The previous responses didn't fully answer your questions. Mixing bleach, or sodium hypochlorite with muriatic acid will liberate chlorine gas, which is definitely toxic, and a severe irritant to eyes and nasal passages and the lungs even in small amounts.

Lyle Kirman
water treatment systems - Cleveland, Ohio

September 24, 2009

A. It's simple really, I work with chemicals all day long with swimming Pools and I was working with a former employee and he mixed the two by accident, it created a white toxic gas and nearly killed us both. The acid is strong if breathed in but is deadly if mixed with chlorine. if breathed in, it's fatal.

Chaz Farmer
- Atwater, California

January 26, 2010

A. Basically the combination of Muriatic Acid and Chlorine is mustard gas or a compound much like it. Very bad stuff, highly toxic and deadly in even small amounts. I spilled a small amount of acid on the floor where there was a small amount of chlorine powder from tablets for the pool and it made a fair amount of dirty cloud appearing gas. I breathed in a small amount before I got out and had lung and breathing problems for 6 months to a year afterwards.

Chris Hatfield
- Two Harbors, Minnesota

August 12, 2011

To Chris Hatfield above:
Mixing Muriatic (hydrochloric) acid and Chlorine is *definitely not* 'Mustard Gas'. Mustard is synthesized from rapeseed plants (using other chemicals and processes), the same place we get "canola" oil from. HCl and Cl mixing as mentioned in other posts here will produce Chlorine Gas, which is a true gaseous substance, while Mustard is distributed as an aerosol or droplet form, not a gas. The term 'gas' in 'Mustard Gas' is a misnomer. It got that name in WWI, where the use of chemical agents in warfare is well known - everyone simply called the agents 'gas' because it was a simpler term to use on the battlefield. Tragically, both sides of the conflict used Mustard and Chlorine Gas to great effect.

John Dough
chemical demilitarization - Norfolk, Virginia, USA

October 18, 2010appended

Q. Hi, I'm in the concrete application business. I usually mix a solution of Chlorine and a degreaser to wash concrete. I also etch concrete by mixing a solution of Muriatic acid and water: 1/3.

I mistakenly added acid to chlorine thinking the chlorine was water and I got one hell of a reaction. What took place chemically?

Ray D.deleted
contractor - largo Florida USA

October 18, 2010

A. Hi, Ray. As you see, we appended your inquiry to a previous similar thread which may answer it for you. You're probably lucky to be alive! For one thing, this reaction releases chlorine gas and other toxic gasses. Sodium hypochlorite or calcium hypochlorite is basically chlorine gas dissolved into a watery alkaline solution. If you destroy the alkalinity by adding acid, you destroy the liquid's ability to keep the chlorine gas in solution, and it is all suddenly released as an inhaleable gas.

You need written procedures that preclude it happening again. Good luck.


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Ted Mooney, P.E. RET
Pine Beach, New Jersey

January 18, 2011

Q. I just accidentally pumped some chlorine into what I thought was an empty 1 Gal Milk jug.
It contained Muriatic acid (very little). It made a reaction & I took 1/2 a breath (scared reaction).
I feel Okay; eyes a little blurry.
Do I need to see a doctor?
Thank You

Daniel Greene
Hobbyist - Castaic, California USA

January 19, 2011

A. Hi, Daniel. Call the doctor's office. The nurse answering the phone will ask you some questions and decide whether she thinks you should visit. If the person answering is not a qualified nurse who can help you, that indicates that you should be seeing a doctor but not that one :-)


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Ted Mooney, P.E. RET
Pine Beach, New Jersey

December 15, 2011

Q. I do a lot of swimming in chlorinated swimming pools. On average, I will swim 5 times a week for 40 minutes a day (lap swim for exercise). This is a public olympic sized pool with very significant vertical clearance between the pool and the ceiling (about 100 feet).

What are the long term health consequences if any from repeated exposure to chlorine in the water?

How does the absorption of chlorine through the skin affect the acidity/alkalinity levels of the blood? Does it make the blood more acidic or alkaline, or is there no impact?

Please advise.


Tom Cavanaugh
- Dallas, Texas

February 20, 2013

Q. I work on a farm; we mix hypochlorite acid with a dash of washing up liquid to clean the parlour walls. Very strong smell ... is this safe?

adam hart
- england, shropshire

February , 2013

A. Hi Adam. I'm not here to be a stickler, but firstly there is no such thing as hypochlorite acid, and secondly "washing up liquid" tells us nothing about what chemicals you are talking about. You can't be that casual and then ask questions about what you are doing :-(

Diluted bleach is often used as a disinfectant, but if the smell is too strong, you need to make it up more dilute. If "washing up liquid" means only hand soap or dish detergent for hand-washing dishes, you can add it to diluted bleach without a problem.


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Ted Mooney, P.E. RET
Pine Beach, New Jersey

February 23, 2013

Q. Sorry Ted for being so vague. Been at work today and had a look and it's a sodium hypochlorite solution which we're mixing with normal house-hold washing up liquid.
Rough average mix is one large bucket of hypo to quarter a cup of washing up liquid.
Any idea if this is safe as the fumes are quite strong!
Appreciate any advice.


adam hart
- england, shropshire

February 24, 2013

A. Hi again. The more we learn, the more we learn that there is no such thing as safe and unsafe . . . it's all relative. So if it smells really strong, simply make it up weaker.

I don't know why you are doing this anyway. I have heard of disinfecting once to stop mold after a flood, and I've heard of washing down a bathroom with diluted bleach, but I'm not familiar with anyone making a habit of washing their parlor walls with bleach. Unless your parlor is also your abattoir, I'd suggest stopping :-)


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey
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