CABT Healthcare and Electrical Safety 2 — Questions and Answers
Question 1: Which class of electrical equipment relies solely on basic insulation for protection and has no grounding conductor?
- Class I
- Class II
- Class III
- Class 0 (Correct answer)
Correct answer: Class 0
Class 0 equipment relies only on basic insulation with no additional safety measure such as grounding or protective extra-low voltage.
Question 2: The maximum allowable chassis leakage current for a patient-connected device in a general care area per NFPA 99 is:
- 10 µA
- 100 µA (Correct answer)
- 500 µA
- 1 mA
Correct answer: 100 µA
NFPA 99 allows a maximum chassis leakage current of 100 µA for patient-connected devices in general care (Category 2) areas.
Question 3: In a patient care environment, 'equipotential grounding' primarily protects against:
- Voltage surges from lightning
- Microshock from potential differences between grounded surfaces (Correct answer)
- Radio-frequency interference
- Electrostatic discharge from staff clothing
Correct answer: Microshock from potential differences between grounded surfaces
Equipotential grounding ensures all conductive surfaces in a patient care area are at the same potential, preventing microshock from small current flow through the patient.
Question 4: A biomedical technician discovers that the ground pin of a 3-prong medical device plug is broken. The safest immediate action is to:
- Replace the fuse and return to service
- Tag out the device and remove it from service (Correct answer)
- Use a 2-to-3 prong adapter until parts arrive
- Continue use if the device passes a visual inspection
Correct answer: Tag out the device and remove it from service
A broken ground pin eliminates the primary fault-current path, creating a shock hazard; the device must be removed from service immediately.
Question 5: Which test instrument is used to measure the insulation resistance of medical electrical equipment to detect degraded insulation?
- Clamp meter
- Oscilloscope
- Megohmmeter (megger) (Correct answer)
- Digital multimeter set to AC volts
Correct answer: Megohmmeter (megger)
A megohmmeter applies a high DC test voltage (typically 500 V) and measures the resulting resistance to assess insulation integrity.
Question 6: When performing an electrical safety inspection, a 'point of care' device is found to have a leakage current of 450 µA chassis-to-ground. This finding indicates:
- Normal; within all accepted limits
- Elevated; exceeds the 100 µA general care limit but acceptable in critical care
- A safety hazard requiring removal from service (Correct answer)
- Acceptable only if the device is double-insulated
Correct answer: A safety hazard requiring removal from service
450 µA exceeds both general care (100 µA) and critical care (10 µA) NFPA 99 chassis leakage limits, making the device unsafe for use.
Question 7: The purpose of an isolation transformer in a line isolation monitor (LIM) system is to:
- Step down voltage to 12 V for patient circuits
- Isolate the power circuit from earth ground to reduce shock hazard (Correct answer)
- Filter harmonics from medical imaging equipment
- Provide backup power during an outage
Correct answer: Isolate the power circuit from earth ground to reduce shock hazard
An isolation transformer breaks the direct connection to earth ground, so a single fault does not complete a shock circuit through a grounded patient.
CABT Healthcare and Electrical Safety 2
Which class of electrical equipment relies solely on basic insulation for protection and has no grounding conductor?