Phosphorus trichloride is a water-reactive, corrosive, oxidizing, reactive, volatile, colorless-toslightly yellow, fuming liquid with a pungent, irritating odor. It is used to manufacture dyes, gasoline additives, germicides, pesticides, medicines, plasticizers, surfactants, and many other chemicals. It is also found in industrial settings where the surface metallization of rubber is performed.


Phosphorus trichloride is not flammable, but it is a strong oxidizing agent and will support combustion. It has a specific gravity of 1,575, a molecular weight of 137.35, and a vapor density of 4.75. It boils at 168.8°F, freezes at – 169.2°F, and reacts violently with water, liberating toxic and flammable gases, acids, and free phosphorus and producing spontaneous fires. Its chemical formula is PCI,.


Phosphorus trichloride is such a hazardous material that it is difficult to rank its various hazards. Since contact with water produces so many additional, extreme hazards, we will discuss them first.

Large amounts of heat are generated when water or moisture in the air contacts phosphorus trichloride, and one of the gases formed is phosphine, a spontaneously flammable material. This means that fire will be present any time water contacts the product. Hydrogen chloride, an irritant gas, is also generated when phosphorus trichloride and water mix. Hydrogen chloride is very soluble in water, and when it is generated in this reaction it will probably dissolve in the excess water involved in the incident. When it does, hydrochloric acid is formed. (For a more complete discussion of hydrogen chloride, see the February 1988 issue of Fire Engineering.)

The water reaction also produces free phosphorus, another spontaneously flammable material. As it burns in air, phosphates and phosphites are produced, which in turn form phosphorous acids.

It is not necessary for phosphorus trichloride to contact a pool or stream of water for the aforementioned reactions to occur. They are possible (although on a smaller scale) when the release occurs in a very moist atmosphere or if the spill is exposed to rainfall.

Phosphorus trichloride is a powerful corrosive and will seriously damage human tissue. Physical contact with the liquid causes severe burns and permanent damage to eyes or skin, as might contact with vapors. Ingestion of the liquid causes severe damage to the mouth, esophagus, stomach, and any other organs it contacts. At the same time, contact of the product with the moisture in the mouth and esophagus may generate heat and the hazardous materials mentioned above.

Inhalation of phosphorus trichloride vapors causes severe damage to the lungs and mucous membranes. In some cases, symptoms caused by damage to the lungs may be delayed for eight to 36 hours, and such damage may be severe enough to produce a deadly filling of the lungs with liquid caused by pulmonary edema. The TLV-TWA (threshold limit value—time weighted average) for phosphorus trichloride is 0.2 ppm, while the STEL (short-term exposure limit) is 0.5 ppm for 15 minutes.


Phosphorus trichloride is a very reactive chemical, producing violent reactions with materials other than water. It may react explosively with such metals as aluminum, sodium, and potassium and such materials as acetic acid, nitrous acid, nitric acid, and chromyl chloride. Other violent reactions may occur between phosphorus trichloride and any oxidizers and alkalis; individual chemicals such as hydroxylamine, dimethyl sulfoxide, iodine monochloride, and lead dioxide; and most organic materials. Any contact of the product with a metal may liberate hydrogen, a highly flammable (and explosive) gas.

Phosphorus trichloride may act as an oxidizing agent in many reactions, helping to support the combustion it produces. Any contact with ordinary combustibles will make those materials very flammable, while contact with very flammable materials may cause them to be explosive.


In a release of phosphorus trichloride (as well as any hazardous material) you must notify the proper environmental authorities immediately. Many fire departments will not alert environmental authorities until they have positive identification of the material released. This may delay containment of the product or may cause incorrect procedures to be used that might harm the environment. It is not necessary to know the exact identification of the product before notifying environmental authorities.

Of course, if lives are in danger, certain mitigation techniques that will spread the contaminants and harm the environment may be necessary to save those lives. Life safety is always the first duty of emergency responders, but you must recognize that you may be called on after the incident to explain your actions, especially if such actions spread the contamination.

Since phosphorus trichloride is such a volatile liquid, any release will produce very dangerous vapors that will affect anyone exposed to them downwind. Even if there is a leak in the container above the liquid level, those hazardous vapors will be released. Since the vapor density of phosphorus trichloride is 4.75, those vapors will “hang together” and move downwind unless dispersed by a strong breeze. Therefore, first consider evacuation of all exposed geographical areas.

A common mitigation technique used to disperse the harmful vapors of a released liquid is a high-pressure water spray or fog. However, since the reaction between phosphorus trichloride liquid and water generates hazardous gases upon contact, the incident commander must decide whether or not to introduce water deliberately. He must consider the harm the released product may cause if the dispersing technique is not used, the ability to contain the spill safely, the additional hazardous gases formed by water contact, and the ability to control the runoff created by the technique. Water spray must not contact the liquid itself but must be used downwind of the spill.

The decision to use water spray may be the most feasible alternative, especially if there is a lot of moisture in the air, which will promote reactions anyway. It may be better to control the reactions with water spray or fog, which in turn might disperse the hazardous gases created by the spray. At the very least, attempt the technique on a limited basis to determine whether it will help or worsen the situation. If it does not worsen the situation, use it to lessen the danger zone. Remember, any runoff created by this procedure must be contained.



(Chemical Abstract Services)



(Standard Transportation Commodity Code)



(Registry of Toxic Effects of Chemical Substances)



(United Nations/North America)



(Chemical Hazard Response Information System)



(U.S. Department of Transportation)


NFPA 704 Rating



(International Maritime Organization)

8.0, corrosive


Efforts must be made to contain the original spill. If the leak is small enough, plugs should be driven into the container to seal it. Any plugs and tools used in any mitigation technique must be compatible with (and not attacked by) phosphorus trichloride. Containment ponds may be created by surrounding the spill area with built-up dikes of sand, soil, clay, and other materials. Phosphorus trichloride is an oxidizing agent, so contact with organic material mixed in with the diking material may be easily ignited.

If the proper excavation equipment is available (with operators properly protected), a containment pit may be dug to hold the liquid, which may be led to the pit by trenches. A pit may be preferable to a containment pond if it has a smaller surface area, because the evolution of vapors is greater from a liquid that has a greater surface area. It will be easier to cover a smaller area with an impervious material to slow the evolution of vapors.

The use of foam to slow evaporation may be tricky. Since foams are water-based and phosphorus trichloride is a water-reactive material, contact of the foam with the surface of the liquid may speed up the production of harmful vapors. It is a good idea to contact foam suppliers to see if any history is available on this material.

The mitigation technique called neutralization could reduce vapor evolution by converting the phosphorus trichloride to a less reactive material. Manufacturers of phosphorus trichloride can provide the names of any chemicals capable of neutralizing it. One reference recommends the use of soda ash (sodium carbonate) or crushed limestone (calcium carbonate) to neutralize the acid formed by the reaction of phosphorus trichloride with water.

Dilution, a mitigation technique whereby enough water is added to another material to reduce its hazards, is a special option in special cases. First, the volume of spilled material must be small; second, there must be virtually no exposure hazard, human or otherwise; third, the proper volume of water must be available; and fourth, emergency responders must be prepared for the initial violent reactions caused by the water.

Absorption of the product may be accomplished by adding such materials as cement powder, clay, diatomaclous earth, fly ash, fuller’s earth, sand, soil, or other dry, mineral-type materials. Once the material is absorbed, the contaminated absorbent must be disposed of in compliance with federal, state, and local regulations.


chloride of phosphorus phosphorous chloride phosphorus chloride phosphorus (III) chloride


If the product has been contained in a pit or pond, professional salvage companies using the proper compatible equipment can pump or suction it into secure containers. Salvage and/or cleanup operations should not be performed by emergency response personnel unless they are properly educated, trained, and equipped for such procedures. Instead emergency responders should concentrate on the protection of human life, the environment, societal systems, and property by working only on containment activities.

No matter what salvage or cleanup activities are performed, keep in mind that some of the product will seep into the surrounding soil, and this area of contamination also must be removed. The contaminated soil must be treated in the same manner as the pure product, since the product is still present. Environmental authorities will test the soil in the spill area to determine the extent of necessary excavation and soil removal.

Avoid contact of the liquid with metals, since contact with most metals will corrode them and liberate flammable and explosive hydrogen gas. This reaction will occur when the metals are wet or damp.

Prevent entry of phosphorus trichloride into sewers or waterways. If the liquid enters a sewer containing water, the hazardous gases mentioned earlier may rapidly fill the sewer system. These reactants, especially phosphine, may ignite other flammable sewer gases (such as methane) and cause disastrous explosions. Notify all sewage treatment facilities immediately so they can prepare for eventual contamination.

If the liquid reaches a waterway, the dangerous reactants already mentioned will be produced immediately, accompanied by flashes of fire. If the flow of the waterway cannot be immediately diverted to a holding area for purification or if the contamination cannot be prevented from moving downstream, the environmental authorities must monitor that downstream water. Notify all downstream users of the water immediately, and the environmental experts will determine when the water is once again safe.

Contaminated water that has been diverted and contained may be treated in several ways, one of which is with chemicals that will remove any hazardous reactants. Care must be taken if any free phosphorus has been formed, since it will begin to burn once it is exposed to air. Gases may be removed by aeration techniques including sparging and air stripping. Acids formed may be neutralized by adding the proper neutralizing agents (again, consult the manufacturers of phosphorus trichloride for the proper material). If the water cannot be totally decontaminated, it may have to be removed and disposed of in the same manner as the contaminated soil and sorbents.



Any container exposed to the flames or radiated heat of a fire will be subject to catastrophic failure due to pressure rising beyond the design strength of the container. In this event hot, vapor-producing, highly reactive liquid will be spread over a wide area. The hot liquid will be many times more reactive than it is at normal (or room) temperature. The speed of any chemical reaction doubles for every 18°F temperature rise.

Hazardous gases and other reactants will be produced at a rapid rate, and the oxidizing nature of these reactants will make any fire burn hotter and faster. Any metal contacted will be corroded quite rapidly, and the introduction of water by firefighters could increase the production of hazardous reactants.

Even though the material is waterreactive, water must be used in an attempt to keep the containers cooled below temperatures that will cause them to explode. This water should be applied in flooding quantities from as far away as possible using unmanned appliances.


For inhalation, remove the victim to fresh air and keep warm and quiet. Administer artificial respiration if breathing stops or becomes difficult; be careful of exposure to the product in the victim’s lungs or vomit. Get medical attention as soon as possible.

For eye contact, seek immediate medical attention. Until it is provided, flush the eyes with water for at least 15 minutes, lifting the lids periodically-

For skin contact, remove all contaminated clothing and wash all contacted areas with large amounts of water. Immediate medical attention is necessary.

For ingestion, have the victim drink large quantities of water. Do not attempt to make the victim vomit, and never try to make an unconscious person drink anything. Seek medical attention immediately.


Choose clothing and protective equipment that prevent contact of phosphorus trichloride liquid or vapor with the eyes, skin, and respiratory system. Select splashproof chemical goggles and a face shield for eye protection and use positive-pressure, self-contained breathing apparatus. Rubber boots, gloves, and aprons and other impervious clothing will offer some protection but will degrade in a short time. If total encapsulating suits are worn (and they should be if contact with the product is possible), at least one reference claims that material such as polytctrafluorocthylene (FI FE or Teflon) may protect for exposures of up to four hours.

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