How Long Does It Take To Knock Out A Person Using Chloroform?

Chloroform is a colorless, sweet-smelling liquid with the IUPAC name Trichloromethane and a chemical formula CHCl3. Chloroform is used as a solvent in paper, building and wood processing industries, as well as in pesticide production. Chloroform can also daze or knock people unconscious, even when consumed in small doses.

Pick any famous crime thriller, serial killer investigation or espionage movie and chances are good that you’ll find the following scene unfolding in one way or another:

A villain/hero sneaks up behind a target and places a rag over their mouth; after a few moments, the victim goes weak in the knees and loses consciousness.

If you’re more interested in chemistry than action scenes, then this question has surely popped into your head at some point: does chloroform (the liquid that they soak the rag in) really knock someone out that quickly?

What is Chloroform?

Chloroform is a colorless, sweet-smelling organic compound with the IUPAC name Trichloromethane and the chemical formula CHCl3. It is a dense liquid that has tetrahedral molecular geometry with C3 symmetry. The structural formula of chloroform is given below:

Chloroform's structural formula

Chloroform’s structural formula

As mentioned earlier, chloroform is a highly volatile liquid that has been widely used for its anesthetic properties throughout history. Due to such potent properties, it has a reputation for being able to daze or knock people unconscious, even when it’s consumed in small doses.

In chemistry jargon, chloroform is liquid trichloromethane, and is prepared on an industrial scale by heating a mixture of chlorine and either chloromethane or methane (Chemistry enthusiasts, that was for you!)

chloroform preparation reaction 1

Where is chloroform normally found?

Chloroform is a naturally-occurring organic compound that can be found in the air and in coastal waters, lakes, inland rivers and groundwater. However, most of the chloroform you come across in the environment is produced by humans.

Higher levels of chloroform can be found in industrial areas and in the air above swimming pools where the water has been disinfected with chlorine.

What does chloroform smell like?

Chloroform is a sweet-smelling liquid, somewhat like ether, along with a slightly sweet taste. Some people compare the smell to the odor of disinfectants, similar to the aroma you detect in hospitals and medical facilities.

We asked a number of chemists who work in chemistry labs, who stated that the chloroform smell is vaguely similar to the smell of acetone (an organic compound).

Chloroform uses: What is Chloroform used for?

  1. Chloroform is widely used as a solvent in chemical preparation of compounds.
  2. It is used in paper, building construction and wood processing industries.
  3. It is used in pesticide and film production.
  4. Chloroform is used in the production of a refrigerant called Fluorocarbon 22.
  5. Chloroform is used as a solvent in floor polishes, lacquers, adhesives, resins, oils, alkaloids, fats and rubber.

Use of chloroform as an anesthetic in the past

Chloroform was first used as an anesthetic in the year 1847 by an obstetrician named James Young Simpson; he actually used it on two humans as a means of entertainment.

A few days later, it was successfully used in a dental procedure in Edinburgh with no noticeable harmful repercussions. Soon, its popularity as an anesthetic grew by leaps and bounds, to such an extent that it was even used during the birth of the last two children of Queen Victoria in the 1850s. However, its golden age was brief, as it was gradually replaced by ether (much safer than chloroform, with practically no side effects).

Chloroform effects: What does Chloroform do?

The effects of chloroform exposure on a human increase proportionally with its dosage. In small amounts, chloroform can make you feel lethargic and disoriented, but as the dosage increases, you can quickly become unconscious, unable to feel any pain or sensation. In more severe dosages, it can cause strained breathing, complete muscle relaxation, and paralysis of the chest muscles (which can often be fatal).

Chloroform’s effects on the human body largely depend on its dosage and the method of administration. According to the Wisconsin Department of Health Services, “immediately or shortly after exposure to a level of 100 ppm (100,000 ppbv) of chloroform in the air, a person may feel tired, dizzy, and have a headache.”

Chloroform is well-known for its anesthetic properties. If consumed in mild doses, it can daze or knock a subject out, whereas when consumed in high concentrations, it has the potential to be fatal.

There is s some evidence that chloroform directly impacts the central nervous system, along with the liver and kidneys; in high doses, it can produce respiratory center depression and coma (Source).

Although many of us associate chloroform with ‘a liquid soaked in a rag that knocks people out’, its effects on the human body can be far more complex, and if not carefully monitored, chloroform can be deadly.

How long does it take for Chloroform to knock you out?

While the right dose of chloroform soaked in a rag can definitely knock you unconscious, it would take much longer than what they show in movies (you wouldn’t drop unconscious just by taking a whiff!). With a perfectly measured dose, it would take at least 5 minutes to render someone unconscious.

Volatility issues

Chloroform is a volatile liquid, so it rapidly loses effectiveness when it comes in contact with air. Therefore, the “villain holding a chloroform-soaked rag in his hand while waiting for the victim to appear” is not a plausible scenario, as the chloroform in the rag would lose its effectiveness by the time it was actually pressed against the victim’s nose.

It is possible that a victim in such a situation might not be fainting from the chloroform alone. Along with chloroform, the victim might faint because of suffocation, as placing a rag over the nose and mouth would not allow the victim to breathe.

Chloroform risks: Dangers associated with Chloroform ingestion/consumption

Chloroform, when ingested, is converted to a chemical called phosgene. Phosgene is toxic for cells, so using too much chloroform could cause cells to die.

Looking at the way its usage is portrayed in movies and TV, you might assume it’s just another anesthetic liquid that is harmless to the victim, but that is absolutely false.

Some studies have demonstrated a possible link between the chloroform in chlorinated water and the occurrence of cancer of the colon and urinary bladder. Cancer of the liver and kidneys developed in rats and mice that ate food or drank water containing large amounts of chloroform for extended periods of time.

Chloroform can be very dangerous, to the point of being fatal to a victim if an inappropriate dose is administered or if the chloroform-soaked rag is placed too firmly against their face. The victim may have trouble breathing and suffocate.

There’s a good reason chloroform is no longer used as an anesthetic today; it’s a challenging task to determine the right dosage that would render a person unconscious without impinging other vital nerve functions. Drinking chloroform in even small quantities could prove fatal.

What to do if you’ve been exposed to chloroform?

The first thing to do is get away from the source of exposure as quickly as possible. If the person who’s been exposed is unconscious already and cannot move on their own, they should be removed from the source of chloroform exposure by others.

Articles of clothing that may have come in contact with chloroform should be removed and discarded. Eyes and skin exposed to chloroform should be washed and flushed with clean, uncontaminated water.

Professional medical help should be sought if one is exposed to chloroform, especially in large doses that are generating significant symptoms or side effects.


  1. James Young Simpson
  2. UCLA – School of Public Health
  3. Wisconsin-Department of Health Services
  4. The University of North Carolina
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About the Author

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

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