Authorities in Tianjin say massive explosions and fires this week at a warehouse for hazardous materials have so far not caused any detectable air or water contamination, citing samples taken at 17 locations. However, they say they have no clear picture of what materials were at the transit warehouse at the time of the blasts, because the materials were in temporary storage and the site, owned by Ruihai International Logistics, was badly damaged. Fire and other officials so far have reported detecting calcium carbide, potassium nitrate and sodium nitrate at the site.

Here is a list of some of the chemicals that Ruihui says on its website that it was authorized to handle at the warehouse, and their dangers:

DETECTED AT SITE:

CALCIUM CARBIDE: Noncombustible, but forms flammable gas on contact with water or damp air. Many reactions may cause fire or explosion. Inhalation could lead to coughs, labored breathing, sore throat. When firefighting, only use special powder or dry sand.

SODIUM NITRATE: Noncombustible but enhances combustion of other substances. It gives off irritating or toxic fumes in a fire. Contact may leads to skin redness.

POTASSIUM NITRATE: Noncombustible but enhances combustion of other substances. It gives off irritating or toxic fumes in a fire. Inhalation causes cough and sore threat. Contact may lead to skin redness.

NOT YET CONFIRMED AT SITE:

SODIUM CYANIDE: Noncombustible but forms flammable gas on contact with water or damp air. It gives off irritating or toxic fumes in a fire. Exposure to a large amount of this crystal form of cyanide could lead to convulsions, loss of consciousness, low blood pressure, respiratory failure leading to slow heart rate or death. When firefighting, use foam and power, but no water, no carbon dioxide, and no hydrous agents.

AMMONIUM NITRATE: Noncombustible but enhances combustion of other substances. It gives off irritating or toxic fumes in a fire. Inhalation causes cough, headache and sore throat. When firefighting, use water in large amounts.

TOLUENE DIISOCYANATE: Combustible, gives off irritating or toxic fumes in a fire. Contact with water is not recommended; no open flames. Inhalation of it causes abdominal pain, cough, nausea, shortness of breath, sore throat, vomiting. When firefighting, powder and carbon dioxide are recommended.

METHYL ETHYL KETONE: Highly flammable. Its vapor and air mixtures are explosive. Should not be close to open flames, sparks or smoking. Use powder, foam, carbon dioxide and aqueous film-forming foam in firefighting. Inhalation can lead to cough, dizziness, drowsiness, headache, nausea and vomiting.

NITROCELLULOSE: Highly flammable. Gives off irritating or toxic fumes in a fire. Should stay away from open flames, sparks and smoking. Use water in large amounts in firefighting.

SULFUR: Combustible. Finely dispersed particles form explosive mixtures in air. Should be kept from open flames, sparks and smoking. Use water spray, foam, powder, dry sand in firefighting. Inhalation causes burning sensation, cough and sore throat.

FORMIC ACID: Combustible. It may form explosive vapor or air mixtures above 69 degrees Celsius. Use powder, alcohol-resistant foam, water spray, and carbon dioxide in firefighting.

METHACRYLIC ACID: Combustible. It may form explosive vapor above 77 degrees Celsius. Use aqueous film-forming foam, alcohol-resistant foam, powder, and carbon dioxide in firefighting.

SODIUM SULFIDE: Combustible. Should be kept away from open flames, sparks and smoking. No contact with acids or oxidants. Use water in large amounts, water spray, foam and dry powder in firefighting.

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Source: U.S. Centers for Disease Control and Prevention.