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Hazardous Area and Ex Quiz

Test yourself with 20 multiple choice questions. Check your answers to get a score and an explanation for every question.

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Hazardous Area and Ex Quiz: 20 Questions

Choose one answer for each question, then press Check answers. Explanations appear after checking.

1. Zone 0 means explosive gas is present:

Answer: Continuously or for long periods. Zone 1 occasionally; Zone 2 rarely and briefly. Learn more: Hazardous Area Zone

2. Equipment with EPL Gb is suitable for:

Answer: Zone 1 and Zone 2. Ga Zone 0, Gb Zone 1, Gc Zone 2. Learn more: Equipment Protection Level

3. Hydrogen belongs to gas group:

Answer: IIC. IIC covers hydrogen and acetylene. Learn more: Gas Group

4. Propane belongs to gas group:

Answer: IIA. Most hydrocarbons are IIA. Learn more: Gas Group

5. IIC equipment can be used for:

Answer: IIC, IIB and IIA gases. IIC is the most stringent group. Learn more: Gas Group
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6. T6 equipment has a maximum surface temperature of:

Answer: 85 °C. T6 is the lowest temperature class. Learn more: Temperature Class

7. Intrinsic safety works by:

Answer: Limiting energy. Too little energy to ignite. Learn more: Intrinsic Safety

8. Ex ia protection tolerates:

Answer: Two faults. ia two faults, ib one, ic none. Learn more: Intrinsic Safety

9. For an IS loop, barrier Co must be:

Answer: ≥ Ci + Ccable. Allowed capacitance must cover device and cable. Learn more: Intrinsic Safety

10. Flameproof Ex d enclosures:

Answer: Contain an internal explosion. Flame paths cool escaping gases. Learn more: Flameproof Enclosure
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11. Drilling an extra entry hole in an Ex d enclosure:

Answer: Invalidates the certificate. Only the maker can modify it under certification. Learn more: Flameproof Enclosure

12. Zener barriers require:

Answer: A high integrity IS earth. Fault energy is diverted to earth. Learn more: Intrinsic Safety

13. Zone 21 refers to:

Answer: Combustible dust. Zones 20, 21, 22 are for dust. Learn more: Hazardous Area Zone

14. The Ex marking "Ex db IIC T4 Gb" means suitable for:

Answer: Zone 1, hydrogen, up to 135 °C surface. db flameproof, IIC group, T4 class, Gb Zone 1. Learn more: Equipment Protection Level

15. Area classification for gas is described in:

Answer: IEC 60079-10-1. IEC 60079-10-2 covers dust. Learn more: Hazardous Area Zone
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16. Inspection of Ex equipment follows:

Answer: IEC 60079-17. Initial, periodic and sample inspections. Learn more: Flameproof Enclosure

17. Methane LEL per IEC 60079-20-1 is:

Answer: 4.4 % vol. Older sources used 5 %. Learn more: Lower Explosive Limit

18. A gas detector reading 20 % LEL on methane means about:

Answer: 0.88 % vol methane. 0.2 × 4.4 = 0.88 % vol. Learn more: Lower Explosive Limit

19. Catalytic bead detectors need:

Answer: Oxygen. The gas must burn on the bead. Learn more: Lower Explosive Limit

20. In North America, Zone 1 roughly maps to:

Answer: Division 1. Zones 0 and 1 roughly match Division 1. Learn more: Hazardous Area Zone
0 of 20 answered
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About this Quiz

20 multiple choice questions on hazardous area and ex, the kind asked in instrumentation interviews, technician exams and plant training. Each answer comes with a short explanation, so the quiz works as a revision sheet too.

Show answer key
  1. Continuously or for long periods: Zone 1 occasionally; Zone 2 rarely and briefly. Learn more: Hazardous Area Zone
  2. Zone 1 and Zone 2: Ga Zone 0, Gb Zone 1, Gc Zone 2. Learn more: Equipment Protection Level
  3. IIC: IIC covers hydrogen and acetylene. Learn more: Gas Group
  4. IIA: Most hydrocarbons are IIA. Learn more: Gas Group
  5. IIC, IIB and IIA gases: IIC is the most stringent group. Learn more: Gas Group
  6. 85 °C: T6 is the lowest temperature class. Learn more: Temperature Class
  7. Limiting energy: Too little energy to ignite. Learn more: Intrinsic Safety
  8. Two faults: ia two faults, ib one, ic none. Learn more: Intrinsic Safety
  9. ≥ Ci + Ccable: Allowed capacitance must cover device and cable. Learn more: Intrinsic Safety
  10. Contain an internal explosion: Flame paths cool escaping gases. Learn more: Flameproof Enclosure
  11. Invalidates the certificate: Only the maker can modify it under certification. Learn more: Flameproof Enclosure
  12. A high integrity IS earth: Fault energy is diverted to earth. Learn more: Intrinsic Safety
  13. Combustible dust: Zones 20, 21, 22 are for dust. Learn more: Hazardous Area Zone
  14. Zone 1, hydrogen, up to 135 °C surface: db flameproof, IIC group, T4 class, Gb Zone 1. Learn more: Equipment Protection Level
  15. IEC 60079-10-1: IEC 60079-10-2 covers dust. Learn more: Hazardous Area Zone
  16. IEC 60079-17: Initial, periodic and sample inspections. Learn more: Flameproof Enclosure
  17. 4.4 % vol: Older sources used 5 %. Learn more: Lower Explosive Limit
  18. 0.88 % vol methane: 0.2 × 4.4 = 0.88 % vol. Learn more: Lower Explosive Limit
  19. Oxygen: The gas must burn on the bead. Learn more: Lower Explosive Limit
  20. Division 1: Zones 0 and 1 roughly match Division 1. Learn more: Hazardous Area Zone
Tip: take the quiz before an interview, note the questions you missed and read the linked article for those topics.
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Frequently Asked Questions

Is this quiz free?

Yes. No sign up is needed and you can retake it as often as you like.

Are the answers explained?

Yes. After you check your answers, each question shows the correct answer and a short explanation.

Where can I find more questions?

See the Interview Q&A section of instrumentationblog.in and the linked article below.

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