Which hazardous products cannot be extinguished with water?

Organic matter, inorganic matter... so many dangerous chemicals that cannot be extinguished with water, can be remembered

During the explosion in Tianjin , the firefighters who first rushed to the fire site took the water dragon in a brave attitude and rushed to the scene of the accident in the absence of an open fire. However, the fire has not only ceased, but has intensified, leading to “the biggest firefighter dereliction of duty since the founding of New China”. So, why can't we extinguish with water under any circumstances?

According to the on-site fire headquarters, calcium carbide is stored in the warehouse, and there are also nitrates such as potassium nitrate and sodium nitrate. Wang Ji, a firefighter in Beijing, said, “Different chemicals need different fire extinguishing agents . We must all learn. Calcium carbide reacts with water and cannot use water.” What fire extinguishing agent is used at the site “should be the commander’s decision.” "Calcium carbide is an abbreviation for calcium carbide (CaC2) , which reacts violently with water, generating acetylene (C2H2) and releasing heat. Acetylene is a colorless, highly flammable gas at room temperature and is mainly used for industrial applications such as welding of metals. According to the 2014 acceptance document of the local environmental protection authority , the incident warehouse was designed to store chemicals such as calcium carbide, potassium nitrate and sodium nitrate.

So, what accidents cannot be extinguished with water?

Inorganic matter

If this explosive is ultimately identified as calcium carbide, then calcium carbide is a type of model that cannot be extinguished by water, and the water will accelerate the explosion.

Most of these substances are strongly reductive, for example—

Highly active metals: sodium, potassium, and calcium are well-known, but in fact, lithium, magnesium, and aluminum are also the same. The common feature of these metals is that when they encounter water, they produce hydrogen, which is more explosive than these metals. Therefore, water will exacerbate its combustion explosion;

Highly active metal alloys, hydrides, carbides, etc.: Calcium carbide name calcium carbide, others such as lithium aluminum hydride, sodium hydride, calcium-silicon alloys, especially hydrides, more hydrogen released under the same quality, more prone to explosion;

Highly active metal oxides: The most typical are the quicklime calcium oxide, others such as sodium oxide, although these substances are essentially non-reducible and will not burn, but will encounter a large amount of exothermic water in the case of water and become a hydroxide in the enclosed space. It will also cause an explosion inside;

Non-metallic oxides: typical of P2O5 , these oxides also exothermic in water, although the possibility of explosion is weaker, but these substances react with water and are then strong acids, which can be very troublesome to handle.

Peroxides and other oxidants: strong oxidizers can also be exposed to water explosions, sodium peroxide and other substances are all such, and these substances release oxygen, exposure to flammables will cause secondary disasters;

Some chlorine-containing and nitrogen-containing substances: Typical substances such as magnesium nitride, which will replace with water, react violently. Although no oxidation reaction occurs in the process, a large amount of gas can also cause explosion.

Organic matter

In general, organics have strong reducibility and low density, and they are not very suitable for water extinguishing.

Light oil: These materials have a lower density than water. Although water does not react with them, light oil will float above the water, and it cannot be insulated from oxygen and fire-retardant. Generally when water is used to extinguish such materials , just to cool the air, rather than directly to the burning point;

Alkyl Metals: This is similar to metal hydrides. The most common are butyllithium, triethylaluminum, Grignard reagents, etc., which release flammable gases when exposed to water;

Silanes and their derivatives: These substances usually react with water, get hydrogen, and are relatively prone to explosion;

Organic peroxides: Unlike inorganic peroxides, organic peroxides can explode when exposed to water and are actually more dangerous.

Other reactive groups: such as isocyanate, this type of substance releases carbon dioxide with water, the volume of gas increases, and explosion occurs. For example, acid anhydride may not explode when exposed to water, but it will release a large amount of acid gas. Normally, it will not use water to extinguish the fire.

Other special substances

There are also several special substances: nitrates, diazots, nitro compounds ( TNT , nitrocellulose, etc.). These substances are explosives themselves and they are more difficult to rescue. They can all be used for explosives. Heat or shock can explode and therefore cannot be used directly. Go to the impact and only manage to cool down.

The characteristics of each substance are different. The MSDS will be prepared in industry and the remedial measures for disasters will be listed. Even if the substance does not belong to the above categories, it does not mean that they are safe, and it is still necessary to determine the characteristics before choosing the right one. Fire extinguishing methods.

Similarly, foreign fire protection products must enter China, and only the re-production of a product that meets China's 3C certification standards. If the standard is really good, if the standard is not scientific, it is likely to reduce the performance of the original fire protection product. Turning good products into bad ones, some entrepreneurs with strong security concepts are unlikely to do so, and they may give up the Chinese market, which is detrimental to the sound development of the Chinese fire-fighting market.

This article from the "Fire frontier" Author: Reporter, compiled by Chinese rescue equipment network.