Installing a plexiglass barrier at the reception desk is an example of which category of hazard control?

Correct answer: C. An engineering control

• A. WORK-PRACTICE controls modify the way a task is PERFORMED — one-handed recapping, not passing sharps hand-to-hand, using instruments rather than fingers for retraction.
• B. ADMINISTRATIVE controls change POLICY and how work is organised — screening patients on arrival, staggering appointments, sending symptomatic staff home, immunisation and training programmes.
• C. CORRECT. ENGINEERING CONTROLS are PHYSICAL modifications to the workplace that ISOLATE or REMOVE the hazard at its source, independent of how any individual behaves. A plexiglass shield does exactly that. Other dental examples: sharps containers, needle-recapping devices, self-sheathing needles, rubber dam, high-volume evacuation, and negative-pressure or high-efficiency ventilation.
• D. PPE is the barrier worn on the BODY — mask, respirator, eye protection, gown, gloves. It sits at the BOTTOM of the hierarchy because it protects only the individual wearing it and only if worn correctly every time.

Note: The NIOSH hierarchy of controls, most to least effective: ELIMINATION → SUBSTITUTION → ENGINEERING → ADMINISTRATIVE → PPE. Exam items commonly ask you to classify a specific measure; the test is whether the control acts on the HAZARD (engineering) or on the PERSON (PPE).