Understanding Chemical Classification

2025-10-28

In a laboratory safety management system, hazardous chemical classification determines reagent storage methods, equipment selection criteria, emergency response plans, and is directly linked to personnel protection levels. Discussing safety without considering classification is like traveling a long distance without a map. All risk prevention and control measures will lose their precise direction and may even lead to irreversible accidents.

EXPLOSIVE：GB 30000.2-2013

• Core Characteristics: Violent reaction under heat, impact, or other stimuli, resulting in instantaneous release of gas and heat, leading to explosion.

• Typical Examples: TNT, ammonium nitrate, and sodium azide with a purity greater than 90%.

• Key Control Points: Store in an explosion-proof cabinet (15-25°C, grounded and anti-static); use copper/anti-static tools, and remove ≤50g at a time; cover leaks with dry fine sand; do not use water.

FLAMMABLE GAS：GB 30000.3-2013 to 6-2013

• Core Characteristics: Gases are classified into three categories: flammable (hydrogen, methane), oxidizing (oxygen, chlorine), and toxic (ammonia, hydrogen sulfide). Some gases present multiple risks.

• Key Control Points: Gas cylinders must be secured with anti-tip brackets. Flammable and oxidizing gases must be kept ≥5 meters apart. Toxic gases must be handled in a fume hood equipped with a detector (alarm threshold: 50% safe concentration). In case of leaks, close the valve immediately. Flammable gases must be diluted with nitrogen, and toxic gases must be covered with absorbent cotton.

FLAMMABLE LIQUID：GB 30000.7-2013

• Core Characteristics: Closed-cup flash point ≤ 60°C. Flash points are categorized into three levels: low (≤ -18°C, such as ether), medium (-18°C-23°C, such as ethanol), and high (23°C-60°C, such as xylene).

• Key Control Points: Store low/medium flash point liquids in explosion-proof refrigerators (≤ 4°C). Heating with open flames is prohibited; water baths are preferred. Use carbon dioxide/foam extinguishers; do not use water.

FLAMMABLE SOLID：GB 30000.8-2013 to 13-2013

• Core Characteristics: Flammable solids (red phosphorus, sulfur powder) ignite easily when heated; pyrophoric substances (yellow phosphorus) spontaneously ignite when exposed to air; pyrophoric substances (sodium, potassium) react with water to produce hydrogen and release heat.

• Key Control Points: Keep flammable solids away from oxidizers; immerse yellow phosphorus in water; store sodium in kerosene; and cover leaks with dry sand.

TOXIC SUBSTANCES：GB 30000.18-2013

• Core Characteristics: Classified by LD50/LC50 as highly toxic (potassium cyanide, LD50 < 5 mg/kg), highly toxic (mercury), or toxic (carbon tetrachloride), potentially harmful to humans through contact or inhalation.

• Key Control Points: Highly toxic substances must be managed with a "two-person, two-lock" system, with access and use registration required; operators must wear respirators and nitrile gloves; and waste liquids must be disposed of harmlessly (e.g., potassium cyanide must be oxidized with sodium hypochlorite).

CORROSIVE SUBSTANCES：GB 30000.19-2013

• Core Characteristics: They are classified as acids (concentrated sulfuric acid, hydrofluoric acid) and alkalis (sodium hydroxide). Contact with biological tissue can cause necrosis, and some are also toxic.

• Key Control Points: Store acids in polypropylene cabinets, alkalis in polyethylene cabinets, and hydrofluoric acid separately. Wear double gloves when handling hydrofluoric acid and have first aid gel available. Rinse burns with clean water for 15 minutes. Neutralize acid burns with sodium bicarbonate and alkali burns with boric acid.

Mixing oxidizers (such as potassium chlorate) with flammable solids (such as sulfur powder) can cause spontaneous combustion due to slight vibrations. Mixing strong acids (such as hydrochloric acid) with strong bases (such as sodium hydroxide) can cause a violent exothermic reaction, leading to rupture of reagent bottles. Demarcating storage areas by category (such as explosion-proof areas, highly toxic areas, and corrosive areas) and clearly marking them can completely avoid these risks.

Different types of hazardous materials require specific protective equipment. Wearing only a standard mask when handling toxic gases (such as ammonia) can lead to ammonia poisoning. Wearing latex gloves when handling corrosive substances (such as hydrofluoric acid) can corrode and cause skin burns. Matching protective equipment to the specific type (e.g., a gas mask for toxic substances, chemical-resistant gloves for corrosive substances) can minimize the risk of injury.

Improper handling can multiply the risk. For example, using water to extinguish a flammable liquid fire (such as ether) can cause the liquid to spread, spreading the fire from a localized area to the entire area. Dousing a leaked substance that becomes flammable upon contact with water (such as metallic sodium) with water can generate hydrogen and cause an explosion. Developing a categorized emergency plan (e.g., using foam extinguishers for flammable liquids and covering flammable substances with sand) can quickly control the situation and minimize losses.

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