General Environmental Requirements for Laboratories

In the design of general laboratories, it is necessary to clearly define the requirements for laboratory environmental conditions. To ensure the quality of analytical testing, the laboratory environment must meet the following conditions:

(1) Meet the requirements of the laboratory’s operational tasks. In particular, chemical analysis rooms and instrument rooms must meet the technical requirements for the use and maintenance of the corresponding instruments and equipment. General requirements for some precision instruments are as follows:

① Power supply voltage: 220 V ± 10%, frequency: 50 Hz ± 0.5 Hz;

② Room temperature: (25 ± 5) °C;

③ Humidity: 40%–70%;

④ No vibration, electromagnetic interference, or direct sunlight;

⑤ Noise levels in instrument rooms should be less than 55 dB; noise levels in work areas should not exceed 70 dB.

(2) The laboratory should provide a good working environment, maintained in a clean and orderly condition, with written rules and regulations to follow.

(3) The laboratory must be equipped with ventilation facilities, necessary safety protective equipment, and fire extinguishers.

An unsuitable laboratory environment can directly affect the accuracy of test results. For example: if the temperature is too low, the variability of balances increases; if humidity is too high, the performance of electronic and optical instruments deteriorates; airborne particles and contaminants have a significant impact on trace analysis; even smoking indoors can affect analytical results.

Management of Laboratory Chemicals

Laboratories require a wide variety of chemicals and reagent solutions. Since most chemicals are toxic and hazardous to some degree, strengthening their management is not only necessary to ensure the quality of analytical data but also to ensure safety.

Laboratories should only store small quantities of chemicals needed for the short term. Chemicals should be stored by category: inorganic compounds can be classified as acids, bases, and salts; among salts, they can be arranged according to the order of metallic elements in the periodic table, such as potassium salts and sodium salts; organic compounds can be classified by functional groups, such as hydrocarbons, alcohols, phenols, aldehydes, ketones, and acids. Additionally, they can be categorized by application, such as standards, indicators, and chromatographic stationary phases.

Classification of Common Hazardous Chemicals

Based on the hazardous properties of chemicals, China classifies hazardous chemicals into 8 categories.

① Explosives: Substances that, when subjected to external influences (such as heat, pressure, or impact), can undergo violent chemical reactions, instantly producing large amounts of gas and heat, resulting in an explosion. They generally contain the following structures: 0—0 (peroxides), 0-Cl (carbonic acid or peroxycarbonic acid compounds), N—X (nitrogen halides), N=O (nitrous or nitro compounds), N=N (nitrosamine or nitrosyl compounds), N=C (nitrate compounds), C^C (acetylene compounds, etc.).

② Compressed and liquefied gases: cylinder-packed gases such as acetylene, hydrogen, oxygen, and nitrous oxide.

③ Flammable liquids: liquids with a closed-cup flash point equal to or lower than 61 T.

④ Flammable solids, self-igniting substances, and substances that become flammable upon contact with moisture, such as alkali metal hydrides, calcium carbide, and white phosphorus.

⑤ Oxidizing agents and organic peroxides.

⑥ Toxic substances: solids with an oral LD₅₀ < 500 mg/kg, liquids with an oral LD₅₀ < 2,000 mg/kg; solids or liquids with an LD₅₀ < 1,000 mg/kg following 24-hour skin contact; and solids or liquids with an inhalation LC₅₀ < 10 mg/L for dust, fumes, and vapors.

⑦ Radioactive materials: Materials with a specific activity greater than 7.4 × 10⁴ Bq/kg.

⑧ Corrosive substances: Solids or liquids capable of causing burns to human tissue and damage to metal objects.

Requirements for Storing Laboratory Reagents

① Flammable and explosive reagents must be stored in steel cabinets (with walls at least 1 mm thick) equipped with ventilation openings at the top. It is strictly prohibited to store flammable liquids in containers larger than 20 L in the laboratory. Flammable and explosive chemicals must not be stored in refrigerators (except for explosion-proof refrigerators).

② Two or more compounds that, when mixed or brought into contact, can cause violent reactions, combustion, explosions, or the release of toxic gases are referred to as incompatible compounds and must not be stored together. Such compounds are typically strong oxidizing agents and reducing agents.

③ Corrosive reagents should be placed in plastic or enamel trays or buckets to prevent accidents caused by broken bottles.

④ Pay attention to the shelf life of chemicals; some reagents gradually deteriorate during storage and may even form hazardous substances. Ethers, tetrahydrofuran, furan-2,6-dione, alkenes, liquid paraffin, and similar substances can form peroxides when exposed to air and light; the longer they are stored, the more dangerous they become. Ether, isopropyl ether, butyl ether, tetrahydrofuran, and furan should not be stored for more than one year without the addition of an inhibitor (such as hydroquinone, pyrocatechol, or ferrous sulfate). Once-opened bottles of diethyl ether can be stored for up to 2 years if 1,2,3-hydroxybenzene (0.1 mg per 100 mL) is added.

⑤ Both chemical storage cabinets and reagent solutions should be kept away from direct sunlight and heat sources such as radiators. Reagents that must be protected from light should be stored in brown bottles or wrapped in black paper or black cloth and kept in a dark cabinet.

⑥ If a label on a reagent bottle is found to have fallen off or is becoming illegible, a new label must be affixed immediately. Reagents without labels or with unreadable labels must be treated as hazardous materials; they must be re-identified and handled with care, and must not be discarded carelessly to avoid serious consequences.

⑦ Highly toxic substances must be locked in a dedicated toxic substance cabinet, and a system must be established whereby their issuance requires an application, approval, and registration with signatures from two authorized personnel.