14.2 Biological Safety Cabinets, Sharps & Exposure Control

14.2 Biological Safety Cabinets, Sharps & Exposure Control

Quick Answer: A BSC contains biohazards with HEPA-filtered air—it is not a chemical fume hood. Use safety sharps, never recap by hand, and change sharps boxes at about ¾ full. After a needlestick: wash, report, get evaluated. Follow the exposure control plan and the control hierarchy: engineering → work practice → administrative → PPE.

Domain IV expects the MLA to work safely around aerosol-generating tasks, needles, broken glass, and post-exposure procedures. These topics appear as “what do you do next?” scenarios more often than as pure definitions.

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Biological Safety Cabinets (BSC): Purpose and Limits

What a BSC is for

A biological safety cabinet is an engineered enclosure that uses directional airflow and HEPA filtration to reduce exposure to infectious aerosols and droplets. Depending on class and type, a BSC may protect:

• Personnel (the worker)
• Product (the culture or specimen from room contamination)
• Environment (lab air and exhaust)

Common clinical laboratory uses include:

• Microbiology setup and work with open cultures (often in designated micro areas)
• Tasks with significant aerosol potential from infectious materials
• Certain specimen manipulations required by facility BSL practices

The MLA may load materials, wipe surfaces, or assist under supervision according to training—only perform in-cabinet work you are authorized and competent to do.

BSC is not a chemical fume hood

Exam trap: pouring volatile solvents “in the BSC because it has a fan” is wrong. Solvent vapors can damage HEPA filters, create fire hazards, and are not the design purpose of a standard BSC. Use a chemical fume hood or other approved chemical control for hazardous chemicals.

Good BSC work practices (concepts)

• Confirm the cabinet is certified and within certification date (facility responsibility; do not use a tagged-out cabinet).
• Allow blowers to run as required before and after work (often several minutes—follow SOP).
• Keep the sash at the proper operating height; do not block grilles with paper or supplies.
• Work at least several inches inside the front grill; move arms slowly to avoid disrupting airflow.
• Disinfect the work surface before and after use with approved disinfectant and contact time.
• Do not store excess equipment inside that blocks airflow.
• Know emergency steps if the alarm sounds or power fails (secure work, notify supervisor per SOP).

Class I, II (A2 common in clinical labs), and III cabinets differ in design; the MLA needs the safety idea more than engineering diagrams: open-front Class II cabinets protect worker and product with HEPA-filtered inflow/downflow when used correctly.

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Sharps Safety

Prefer engineering controls

OSHA and modern lab practice emphasize engineering controls that isolate the hazard:

• Safety-engineered needles and winged sets with retractable or shielding features
• Plastic capillary tubes instead of glass when possible
• Self-blunting or needleless systems when clinically appropriate
• Rigid, puncture-resistant sharps containers at the point of use

Work practice controls support engineering controls:

• Dispose of sharps immediately after use—do not leave needles on trays “for later”
• Keep containers upright and within arm’s reach during phlebotomy and processing
• Never break, bend, or shear contaminated needles
• Never remove a used needle from a syringe by hand for reuse
• Activate safety devices as designed, using the one-handed technique the device requires

Recapping: preferred rule

Do not recap needles. Recapping is a classic cause of needlestick injury. If a rare procedure absolutely requires recapping and no alternative exists, only a mechanical device or a one-handed scoop method may be allowed by policy—and many facilities ban recapping entirely. For the MLA exam, the safest default answer is: do not recap; use the safety feature and dispose immediately.

Sharps containers and the ¾ full rule

Sharps containers must be:

• Closable, puncture-resistant, leak-resistant on the sides and bottom
• Labeled or color-coded (biohazard)
• Located as close as feasible to the point of use
• Maintained upright

Replace containers when they reach the fill line—commonly about three-quarters (¾) full. Forcing a syringe into an overfilled box causes rebound sticks. Do not empty a disposable sharps container into another container. Close and remove per policy when full; sealed containers go into the regulated medical waste stream.

Other “sharps” for disposal purposes can include contaminated broken glass, capillary tubes, slides with sharp edges, and scalpel blades—follow facility definitions. Clean unbroken glass may have a separate broken glass box path (Section 14.3).

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Needlestick and Exposure: Immediate Steps

Treat every percutaneous or mucous-membrane exposure as urgent.

Immediate first aid (do this first)

Then:

1. Report immediately to the supervisor, charge tech, or occupational health per the exposure control plan—do not wait until end of shift.
2. Identify the source patient if known so risk assessment and testing can proceed under policy and consent rules.
3. Obtain confidential medical evaluation promptly (baseline testing, HIV/HBV/HCV risk assessment, prophylaxis when indicated).
4. Document the incident on required forms honestly and completely.
5. Participate in follow-up testing and counseling as directed.

Do not:

• Ignore a “tiny” stick because the patient “looks healthy”
• Test the source patient yourself without authorization
• Delay reporting to avoid paperwork
• Apply bleach into a wound as first aid

Post-exposure prophylaxis (PEP), when indicated for HIV risk, is time-sensitive—another reason immediate reporting matters. Occupational health decides medical management; the MLA’s job is first aid, reporting, and cooperation.

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Exposure Control Plan

Under OSHA BBP rules, the employer maintains a written exposure control plan (ECP) that is reviewed and updated periodically (at least annually and when tasks change). Conceptually, the ECP includes:

• Determination of employee exposure (which job titles and tasks have reasonably anticipated contact with blood/OPIM)
• Methods of compliance (engineering controls, work practices, PPE)
• Hepatitis B vaccination program details
• Post-exposure evaluation and follow-up procedures
• Communication of hazards (labels, training)
• Recordkeeping
• Procedures for evaluating safer medical devices (employee input is often required)

You should know where the plan lives (policy manual, intranet, safety office) and the names/roles to call after an exposure. Annual BBP training reviews the ECP highlights.

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Hierarchy of Controls

Safety programs rank controls from most effective to least effective. PPE is essential but is the last line of defense because it depends on perfect human use every time.

Exam wording often asks which control type a safety-engineered needle represents (engineering) versus “wash hands after glove removal” (work practice) versus “annual training” (administrative) versus “wear gloves” (PPE).

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Integrated Scenarios

Scenario A — Wrong hood: A coworker starts evaporating a solvent stock in the microbiology BSC “because the fan is strong.” Stop the practice, move chemical work to a fume hood if approved, and notify the supervisor. BSC ≠ fume hood.

Scenario B — Overfilled sharps: The outpatient draw station sharps box is past the fill line and needles stick out of the opening. Do not push more sharps in. Seal/replace per policy immediately and report the unsafe condition if supplies were not restocked.

Scenario C — Needlestick: During discard, a protruding needle punctures your glove and skin. Wash with soap and water, notify the supervisor now, proceed to occupational health, and help identify the source specimen/patient per policy.

Scenario D — Aerosol task: Opening a pressurized tube or flaring a hot loop (micro) may create aerosols. Use the designated BSC or safety device, wear required face protection, and never bypass centrifuge lid interlocks.

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