Safety

Biological Safety And Standard Precautions

Standard Precautions (CDC) require treating all blood, body fluids, secretions, and excretions (except sweat) as potentially infectious, regardless of patient diagnosis. This replaced the older Universal Precautions and is the foundation of clinical-lab safety. Personal protective equipment (PPE): fluid-resistant lab coat, gloves, and face/eye protection when splashes are possible.

Clinical laboratories handling patient specimens operate at Biosafety Level 2 (BSL-2): agents of moderate hazard transmitted by percutaneous injury, ingestion, or mucous-membrane exposure (e.g., hepatitis B virus, HIV, Salmonella). BSL-2 requires restricted access, biohazard signage, sharps containers, and a Class II biological safety cabinet (BSC) for aerosol-generating procedures. BSL-3 (e.g., Mycobacterium tuberculosis, Coccidioides, Brucella) adds directional inward airflow and respiratory protection.

Under the OSHA Bloodborne Pathogens Standard (29 CFR 1910.1030), employers must offer the hepatitis B vaccine free, provide an exposure-control plan, and follow post-exposure protocols. Order of donning PPE: gown, mask, goggles, gloves; doffing reverses this with gloves first.

Chemical, Fire, And Engineering Controls

Hazard communication uses the Safety Data Sheet (SDS) (16 standardized sections) and the NFPA 704 fire diamond:

• Blue (left) = health hazard
• Red (top) = flammability
• Yellow (right) = reactivity/instability
• White (bottom) = special hazards (OX = oxidizer, W̶ = water-reactive)

Each colored quadrant is rated 0 (minimal) to 4 (severe). A red "4" warns of a highly flammable material requiring no open flame.

Match the fire class to the extinguisher—picking the wrong one is a common exam trap:

• Class A — ordinary combustibles (paper, wood) — water or ABC
• Class B — flammable liquids/gases (alcohol, xylene) — CO₂ or dry chemical; never water
• Class C — energized electrical equipment — CO₂ or dry chemical; never water
• Class D — combustible metals (sodium, magnesium) — dry powder
• Class K — cooking oils/fats

Worked example: a beaker of xylene ignites near an analyzer that is still plugged in. This is a combined Class B/C fire; a CO₂ extinguisher is correct, and water is contraindicated because it spreads the solvent and conducts electricity.

Engineering controls separate hazards from the worker:

• A chemical fume hood protects against toxic vapors and fumes (e.g., concentrated acids) by drawing air away; it does not contain biological aerosols and lacks HEPA filtration.
• A Class II biological safety cabinet protects the worker, the specimen, and the environment from infectious aerosols using HEPA-filtered laminar airflow.

For acid dilution, always add acid to water ("do as you oughta, add acid to water") to dissipate the exothermic heat safely. Concentrated acid spills are neutralized with sodium bicarbonate; mercury and formaldehyde require specific spill kits.

Sharps, Waste Segregation, And Spill Response

Needlestick injury is the leading occupational hazard in the lab. Under the Needlestick Safety and Prevention Act, employers must provide engineered sharps-injury protection (self-sheathing needles, blunt-fill) and maintain a sharps injury log. Never recap needles by hand; dispose immediately in a puncture-resistant, leakproof, labeled sharps container filled no more than three-quarters full. After a percutaneous exposure: wash the site, report immediately, and follow post-exposure prophylaxis per the exposure-control plan; source and exposed-worker testing follow.

Waste must be segregated by stream — a frequent exam point:

Mixing chemical waste into red biohazard bags or autoclaving incompatible chemicals is a common wrong action.

Ergonomics, Radiation, And Emergency Equipment

Know the emergency equipment and when to use each: an eyewash station must deliver tepid water for a full 15 minutes after a chemical splash to the eyes; a safety shower is used for large body splashes; a fire blanket smothers clothing fires; spill kits are matched to the agent (acid, base, mercury, formaldehyde).

Other testable rules:

• RACE for fire response — Rescue, Alarm, Confine, Extinguish; PASS for extinguisher use — Pull, Aim, Squeeze, Sweep.
• No mouth pipetting, eating, drinking, or applying cosmetics in the technical area.
• Compressed-gas cylinders are stored upright and chained.
• A chemical hygiene plan and accessible SDS library are required under the OSHA Laboratory Standard (29 CFR 1910.1450); a designated chemical hygiene officer oversees it.

Worked example: a technologist splashes concentrated sulfuric acid into one eye. The correct first action is to move to the eyewash station and flush continuously for at least 15 minutes while a coworker calls for help, then seek medical evaluation — not to neutralize the eye with base or apply a bandage first. Choosing a longer flush over neutralization is the one best answer because neutralizing chemicals in tissue generates heat and worsens injury.