DGMS Diesel Equipment Safety Circular 2020 – DPM Limits, Ventilation & Exam Notes

📘 DGMS Technical Circular (Approx. No. 1 of 2020) – Diesel Equipment Safety

🔹 1. Why This Circular Was Issued

Increasing use of trackless diesel-powered equipment (Load-Haul-Dump units, dump trucks, drill jumbos, utility vehicles) in underground coal & metalliferous mines.

Problem: Diesel exhaust contains:

Gases: Carbon monoxide (CO), oxides of nitrogen (NO & NO₂), sulphur dioxide (SO₂), hydrocarbons.

Particulate matter (DPM): very fine carbon particles (<1 micron), which can penetrate deep into lungs.

Health hazards: pneumoconiosis, lung cancer, chronic bronchitis.

Safety hazards: sparks from diesel exhaust, poor ventilation → fire or explosion risk in gassy mines.

Thus, DGMS framed standards for permissible exposure, ventilation, equipment approval, and monitoring.

🔹 2. Diesel Particulate Matter (DPM) Standards

8-hour TWA (Time Weighted Average):

Not to exceed 100 µg/m³ of Elemental Carbon (EC).

First Year of Enforcement:

Temporary limit = 120 µg/m³ EC (to allow industry to adapt).

Short-term exposure limits (STEL):

≤ 300 µg/m³ EC allowed for max 30 minutes.

500 µg/m³ EC shall never be exceeded at any time.

📘 Important for exam: These numbers (100, 120, 300, 500 µg/m³) are often directly asked.

🔹 3. Ventilation Requirements for Diesel Equipment

Minimum air velocity:

≥ 45 m/min at the working place.

Restriction in gassy mines:

Diesel equipment not permitted if flammable gas concentration exceeds:

0.1% in metalliferous & Degree-I coal mines.

0.75% in Degree-II & Degree-III coal mines.

Air quantity must be calculated considering engine capacity, emission standards, and workplace size.

📘 Exam Tip: “45 m/min” and “0.1% gas” are direct-favourite numbers in DGMS MCQs.

🔹 4. Equipment Approval & Technical Standards

Only DGMS-approved engines are permitted.

Must be fitted with:

Catalytic converters → reduce CO, hydrocarbons.

Spark arrestors → prevent ignition.

Wet scrubbers or ceramic filters → trap particulates.

Flameproof exhaust systems in gassy seams.

Fuel standards: Low sulphur diesel (<0.05% sulphur) mandatory.

Refuelling rules: Done only at designated places with fire protection.

🔹 5. Monitoring & Sampling of DPM

Personal exposure monitoring:

At least every 3 months (quarterly).

If >50% of limit → monitor monthly.

If >75% → monitor every 15 days.

Sampling method:

NIOSH 5040 protocol – measures Elemental Carbon.

Accredited labs to analyze samples.

Real-time portable EC analyzers can be used for field checks.

Exceedance procedure:

If limits exceeded → immediate corrective steps (ventilation increase, equipment maintenance).

Report to Regional Inspector (DGMS).

If repeated exceedance → suspend diesel use in affected district until compliance restored.

🔹 6. Worker Health & Safety Measures

Health surveillance:

Pre-employment and periodic medical check-ups.

Lung function tests (spirometry), chest X-rays.

PPE (Personal Protective Equipment):

Respiratory masks with P3 filters if near exposure limits.

Emergency safety:

Fire extinguishers and suppression systems in diesel bays.

Flameproof lighting and proper signage.

🔹 7. Exam-Oriented Points

In MMLGS answers, quote the exact limits (100 µg/m³ EC, 45 m/min velocity, 0.1% gas rule).

In Mining Machinery, explain the role of catalytic converters, scrubbers, spark arrestors.

In Oral Exam, DGMS officers often ask practical Qs:

“What will you do if DPM > 100 µg/m³?”

“Can you use diesel equipment in Degree-II gassy seam?” (Answer: Only if gas < 0.75% and ventilation ≥ 45 m/min).

“What protective systems must be fitted on a diesel engine?”

🔹 8. Quick Memory Table

Parameter DGMS Standard 🚦

DPM limit (8-hr TWA) 100 µg/m³ EC

Temporary (first year) 120 µg/m³ EC

STEL (30 min) 300 µg/m³ EC

Never exceed 500 µg/m³ EC

Ventilation velocity ≥ 45 m/min

Flammable gas (metal/Deg-I) 0.1%

Flammable gas (Deg-II/III) 0.75%

Fuel standard Sulphur <0.05%

Engine requirement DGMS-approved, catalytic converter, spark arrestor

🔹 9. Practical Example Q: A diesel LHD is working in a metalliferous mine. Gas at workplace = 0.15%. Can it operate if ventilation velocity = 60 m/min?

Gas exceeds 0.1% (limit for metalliferous) → 🚫 Not permitted, even though velocity is sufficient.

🔹 10. Why This Circular is Important

Integrates Mining Machinery (engine requirements), Ventilation (air velocity), and Safety/Health (exposure monitoring).

Highly probable in DGMS exams → direct numbers (100, 45, 0.1, 0.75).

In viva, quoting this circular shows updated knowledge of modern mechanization hazards.

Full 25-question MCQ set (with 5 options, correct answer ✅, and explanation 📘) based on the DGMS Technical Circular on Diesel Equipment Safety (2020). This will directly help in DGMS First & Second Class Exam Prep (both Coal & Metal).

📝 25 MCQs – DGMS Circular on Diesel Equipment Safety (2020)

Q1. The 8-hour Time Weighted Average (TWA) exposure limit for Diesel Particulate Matter (DPM) is:
A) 50 µg/m³ EC
B) 75 µg/m³ EC
C) 100 µg/m³ EC
D) 120 µg/m³ EC
E) 150 µg/m³ EC

Parameter	DGMS Standard 🚦
DPM limit (8-hr TWA)	100 µg/m³ EC
Temporary (first year)	120 µg/m³ EC
STEL (30 min)	300 µg/m³ EC
Never exceed	500 µg/m³ EC
Ventilation velocity	≥ 45 m/min
Flammable gas (metal/Deg-I)	0.1%
Flammable gas (Deg-II/III)	0.75%
Fuel standard	Sulphur <0.05%
Engine requirement	DGMS-approved, catalytic converter, spark arrestor

✅ Answer: C
📘 Solution: As per the circular, 8-hr TWA limit is 100 µg/m³ of Elemental Carbon (EC).

Q2. During the first year of enforcement, the relaxed DPM limit was:
A) 80 µg/m³
B) 100 µg/m³
C) 110 µg/m³
D) 120 µg/m³
E) 150 µg/m³

✅ Answer: D
📘 Solution: First year → temporary relaxation to 120 µg/m³ EC.

Q3. The maximum short-term exposure limit (STEL) for DPM (≤30 minutes) is:
A) 200 µg/m³
B) 250 µg/m³
C) 300 µg/m³
D) 400 µg/m³
E) 500 µg/m³

✅ Answer: C
📘 Solution: Short-term limit = 300 µg/m³ EC for ≤30 minutes.

Q4. The DPM level that must never be exceeded at any time is:
A) 250 µg/m³
B) 300 µg/m³
C) 400 µg/m³
D) 500 µg/m³
E) 600 µg/m³

✅ Answer: D
📘 Solution: 500 µg/m³ EC is the absolute maximum never to be exceeded.

Q5. The minimum ventilation velocity required for safe diesel equipment operation is:
A) 30 m/min
B) 40 m/min
C) 45 m/min
D) 50 m/min
E) 60 m/min

✅ Answer: C
📘 Solution: Circular mandates ≥45 m/min air velocity.

Q6. In metalliferous mines, diesel equipment shall NOT be used if flammable gas concentration exceeds:
A) 0.05%
B) 0.1%
C) 0.25%
D) 0.5%
E) 1.0%

✅ Answer: B
📘 Solution: Diesel not allowed if gas > 0.1% in metalliferous and Degree-I coal mines.

Q7. In Degree-II & III coal mines, diesel equipment is prohibited if flammable gas exceeds:
A) 0.25%
B) 0.5%
C) 0.75%
D) 1.0%
E) 1.25%

✅ Answer: C
📘 Solution: In higher gassy seams, diesel ban if methane > 0.75%.

Q8. Which DGMS-approved device must be fitted to diesel engines to prevent sparks?
A) Air filter
B) Spark arrestor
C) Turbocharger
D) Water scrubber
E) Flame sensor

✅ Answer: B
📘 Solution: Spark arrestors are mandatory to avoid ignition sources.

Q9. Which of the following is used to reduce CO and hydrocarbons in diesel exhaust?
A) Water scrubber
B) Catalytic converter
C) Air filter
D) Diesel oxidation unit
E) Heat exchanger

✅ Answer: B
📘 Solution: Catalytic converters reduce CO and unburnt hydrocarbons.

Q10. Which fuel standard is mandated for underground diesel equipment?
A) High sulphur fuel
B) Normal commercial diesel
C) Low sulphur diesel (<0.05% sulphur)
D) Kerosene mix diesel
E) Bio-diesel only

✅ Answer: C
📘 Solution: Only low sulphur diesel (<0.05%) is permitted.

Q11. What is the minimum frequency of DPM monitoring under normal conditions?
A) Weekly
B) Monthly
C) Quarterly (3 months)
D) 6 months
E) Yearly

✅ Answer: C
📘 Solution: Monitoring required at least once every 3 months.

Q12. If DPM exceeds 50% of the limit, monitoring must be done every:
A) 7 days
B) 15 days
C) Monthly
D) 3 months
E) 6 months

✅ Answer: C
📘 Solution: >50% → monthly monitoring.

Q13. If DPM exceeds 75% of the limit, monitoring must be done every:
A) 7 days
B) 15 days
C) 30 days
D) 60 days
E) 90 days

✅ Answer: B
📘 Solution: >75% → monitoring every 15 days.

Q14. Which sampling method is prescribed for DPM monitoring?
A) Gravimetric method
B) NIOSH 5040 (EC analysis)
C) Infrared absorption
D) Gas chromatography
E) Laser photometry

✅ Answer: B
📘 Solution: Standard method = NIOSH 5040, measures Elemental Carbon.

Q15. If DPM levels exceed permissible limits, the mine must:
A) Ignore if production is urgent
B) Report to Regional Inspector and take corrective steps
C) Stop operations permanently
D) Only increase fan speed
E) Train workers on PPE only

✅ Answer: B
📘 Solution: Exceedance requires corrective action + report to RI.

Q16. If DPM levels exceed over two successive shifts despite actions, the mine must:
A) Reduce manpower
B) Increase blasting
C) Suspend diesel operation in the district
D) Replace engines with electrical equipment immediately
E) Ventilate naturally

✅ Answer: C
📘 Solution: Diesel operation must be suspended until compliance achieved.

Q17. Which pollutant is the main indicator used for measuring diesel exhaust hazard?
A) Carbon monoxide (CO)
B) Oxides of nitrogen (NOx)
C) Elemental Carbon (EC)
D) Carbon dioxide (CO₂)
E) Hydrocarbons

✅ Answer: C
📘 Solution: DGMS uses EC as proxy for DPM monitoring.

Q18. Which system in diesel engines traps particulates effectively?
A) Turbocharger
B) Ceramic filter / scrubber
C) Air inlet filter
D) Intercooler
E) Fuel injector

✅ Answer: B
📘 Solution: Diesel Particulate Filters (DPF) or scrubbers capture particulates.

Q19. What is the maximum sulphur content allowed in diesel fuel for underground mining?
A) 0.1%
B) 0.075%
C) 0.05%
D) 0.5%
E) 1.0%

✅ Answer: C
📘 Solution: Fuel must be low sulphur (<0.05%).

Q20. Which health test is most important for workers exposed to diesel emissions?
A) ECG
B) Blood test
C) Spirometry (lung function test)
D) Eye test
E) Hearing test

✅ Answer: C
📘 Solution: Diesel exposure → lung impact → spirometry is critical.

Q21. Which PPE is recommended if DPM levels approach the permissible limit?
A) Ear plugs
B) Safety boots
C) Respiratory mask with P3 filter
D) Welding goggles
E) Safety helmet only

✅ Answer: C
📘 Solution: P3 filter masks protect from fine particulates.

Q22. Which statement is TRUE regarding diesel equipment in gassy seams?
A) Allowed at any methane level if velocity > 45 m/min
B) Not allowed if methane > 0.75% (Deg-II/III)
C) Not allowed if methane > 1% (any seam)
D) Always prohibited in metalliferous mines
E) Allowed without restriction in Degree-I mines ✅ Answer: B
📘 Solution: Diesel banned if methane >0.75% in Deg-II/III seams.

Q23. Why is Elemental Carbon used as indicator for DPM?
A) Easier to measure
B) Stable, represents particulate concentration
C) Approved by NIOSH
D) Cost-effective
E) All of the above

✅ Answer: E
📘 Solution: EC is chosen as a reliable marker of DPM.

Q24. Refuelling of diesel equipment underground must be done:
A) Anywhere in mine roadways
B) Only at designated refuelling bays with fire protection
C) Near working face
D) In explosive magazines
E) In workshops only

✅ Answer: B
📘 Solution: Refuelling only in designated bays with fire suppression.

Q25. The main objective of the DGMS Diesel Equipment Circular (2020) is to:
A) Increase production from diesel machines
B) Improve fuel efficiency
C) Protect miners from DPM and gas hazards
D) Reduce electricity use
E) Allow unlimited diesel use

✅ Answer: C
📘 Solution: Core aim = Health & Safety by regulating DPM & ventilation.

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DGMS Diesel Equipment Safety Circular 2020 – DPM Limits, Ventilation & Exam Notes

✅ Answer: C 📘 Solution: As per the circular, 8-hr TWA limit is 100 µg/m³ of Elemental Carbon (EC). Q2. During the first year of enforcement, the relaxed DPM limit was: A) 80 µg/m³ B) 100 µg/m³ C) 110 µg/m³ D) 120 µg/m³ E) 150 µg/m³

✅ Answer: D 📘 Solution: First year → temporary relaxation to 120 µg/m³ EC. Q3. The maximum short-term exposure limit (STEL) for DPM (≤30 minutes) is: A) 200 µg/m³ B) 250 µg/m³ C) 300 µg/m³ D) 400 µg/m³ E) 500 µg/m³

✅ Answer: C 📘 Solution: Short-term limit = 300 µg/m³ EC for ≤30 minutes. Q4. The DPM level that must never be exceeded at any time is: A) 250 µg/m³ B) 300 µg/m³ C) 400 µg/m³ D) 500 µg/m³ E) 600 µg/m³

✅ Answer: D 📘 Solution: 500 µg/m³ EC is the absolute maximum never to be exceeded. Q5. The minimum ventilation velocity required for safe diesel equipment operation is: A) 30 m/min B) 40 m/min C) 45 m/min D) 50 m/min E) 60 m/min

✅ Answer: C 📘 Solution: Circular mandates ≥45 m/min air velocity. Q6. In metalliferous mines, diesel equipment shall NOT be used if flammable gas concentration exceeds: A) 0.05% B) 0.1% C) 0.25% D) 0.5% E) 1.0%

✅ Answer: B 📘 Solution: Diesel not allowed if gas > 0.1% in metalliferous and Degree-I coal mines. Q7. In Degree-II & III coal mines, diesel equipment is prohibited if flammable gas exceeds: A) 0.25% B) 0.5% C) 0.75% D) 1.0% E) 1.25%

✅ Answer: C 📘 Solution: In higher gassy seams, diesel ban if methane > 0.75%. Q8. Which DGMS-approved device must be fitted to diesel engines to prevent sparks? A) Air filter B) Spark arrestor C) Turbocharger D) Water scrubber E) Flame sensor

✅ Answer: B 📘 Solution: Spark arrestors are mandatory to avoid ignition sources. Q9. Which of the following is used to reduce CO and hydrocarbons in diesel exhaust? A) Water scrubber B) Catalytic converter C) Air filter D) Diesel oxidation unit E) Heat exchanger

✅ Answer: B 📘 Solution: Catalytic converters reduce CO and unburnt hydrocarbons. Q10. Which fuel standard is mandated for underground diesel equipment? A) High sulphur fuel B) Normal commercial diesel C) Low sulphur diesel (<0.05% sulphur) D) Kerosene mix diesel E) Bio-diesel only

✅ Answer: C 📘 Solution: Only low sulphur diesel (<0.05%) is permitted. Q11. What is the minimum frequency of DPM monitoring under normal conditions? A) Weekly B) Monthly C) Quarterly (3 months) D) 6 months E) Yearly

✅ Answer: C 📘 Solution: Monitoring required at least once every 3 months. Q12. If DPM exceeds 50% of the limit, monitoring must be done every: A) 7 days B) 15 days C) Monthly D) 3 months E) 6 months

✅ Answer: C 📘 Solution: >50% → monthly monitoring. Q13. If DPM exceeds 75% of the limit, monitoring must be done every: A) 7 days B) 15 days C) 30 days D) 60 days E) 90 days

✅ Answer: B 📘 Solution: >75% → monitoring every 15 days. Q14. Which sampling method is prescribed for DPM monitoring? A) Gravimetric method B) NIOSH 5040 (EC analysis) C) Infrared absorption D) Gas chromatography E) Laser photometry

✅ Answer: C 📘 Solution: Diesel operation must be suspended until compliance achieved. Q17. Which pollutant is the main indicator used for measuring diesel exhaust hazard? A) Carbon monoxide (CO) B) Oxides of nitrogen (NOx) C) Elemental Carbon (EC) D) Carbon dioxide (CO₂) E) Hydrocarbons

✅ Answer: C 📘 Solution: DGMS uses EC as proxy for DPM monitoring. Q18. Which system in diesel engines traps particulates effectively? A) Turbocharger B) Ceramic filter / scrubber C) Air inlet filter D) Intercooler E) Fuel injector

✅ Answer: B 📘 Solution: Diesel Particulate Filters (DPF) or scrubbers capture particulates. Q19. What is the maximum sulphur content allowed in diesel fuel for underground mining? A) 0.1% B) 0.075% C) 0.05% D) 0.5% E) 1.0%

✅ Answer: C 📘 Solution: Fuel must be low sulphur (<0.05%). Q20. Which health test is most important for workers exposed to diesel emissions? A) ECG B) Blood test C) Spirometry (lung function test) D) Eye test E) Hearing test

✅ Answer: C 📘 Solution: Diesel exposure → lung impact → spirometry is critical. Q21. Which PPE is recommended if DPM levels approach the permissible limit? A) Ear plugs B) Safety boots C) Respiratory mask with P3 filter D) Welding goggles E) Safety helmet only

✅ Answer: E 📘 Solution: EC is chosen as a reliable marker of DPM. Q24. Refuelling of diesel equipment underground must be done: A) Anywhere in mine roadways B) Only at designated refuelling bays with fire protection C) Near working face D) In explosive magazines E) In workshops only

✅ Answer: C 📘 Solution: Core aim = Health & Safety by regulating DPM & ventilation.

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✅ Answer: C
📘 Solution: As per the circular, 8-hr TWA limit is 100 µg/m³ of Elemental Carbon (EC).

Q2. During the first year of enforcement, the relaxed DPM limit was:
A) 80 µg/m³
B) 100 µg/m³
C) 110 µg/m³
D) 120 µg/m³
E) 150 µg/m³

✅ Answer: D
📘 Solution: First year → temporary relaxation to 120 µg/m³ EC.

Q3. The maximum short-term exposure limit (STEL) for DPM (≤30 minutes) is:
A) 200 µg/m³
B) 250 µg/m³
C) 300 µg/m³
D) 400 µg/m³
E) 500 µg/m³

✅ Answer: C
📘 Solution: Short-term limit = 300 µg/m³ EC for ≤30 minutes.

Q4. The DPM level that must never be exceeded at any time is:
A) 250 µg/m³
B) 300 µg/m³
C) 400 µg/m³
D) 500 µg/m³
E) 600 µg/m³

✅ Answer: D
📘 Solution: 500 µg/m³ EC is the absolute maximum never to be exceeded.

Q5. The minimum ventilation velocity required for safe diesel equipment operation is:
A) 30 m/min
B) 40 m/min
C) 45 m/min
D) 50 m/min
E) 60 m/min

✅ Answer: C
📘 Solution: Circular mandates ≥45 m/min air velocity.

Q6. In metalliferous mines, diesel equipment shall NOT be used if flammable gas concentration exceeds:
A) 0.05%
B) 0.1%
C) 0.25%
D) 0.5%
E) 1.0%

✅ Answer: B
📘 Solution: Diesel not allowed if gas > 0.1% in metalliferous and Degree-I coal mines.

Q7. In Degree-II & III coal mines, diesel equipment is prohibited if flammable gas exceeds:
A) 0.25%
B) 0.5%
C) 0.75%
D) 1.0%
E) 1.25%

✅ Answer: C
📘 Solution: In higher gassy seams, diesel ban if methane > 0.75%.

Q8. Which DGMS-approved device must be fitted to diesel engines to prevent sparks?
A) Air filter
B) Spark arrestor
C) Turbocharger
D) Water scrubber
E) Flame sensor

✅ Answer: B
📘 Solution: Spark arrestors are mandatory to avoid ignition sources.

Q9. Which of the following is used to reduce CO and hydrocarbons in diesel exhaust?
A) Water scrubber
B) Catalytic converter
C) Air filter
D) Diesel oxidation unit
E) Heat exchanger

✅ Answer: B
📘 Solution: Catalytic converters reduce CO and unburnt hydrocarbons.

Q10. Which fuel standard is mandated for underground diesel equipment?
A) High sulphur fuel
B) Normal commercial diesel
C) Low sulphur diesel (<0.05% sulphur)
D) Kerosene mix diesel
E) Bio-diesel only

✅ Answer: C
📘 Solution: Only low sulphur diesel (<0.05%) is permitted.

Q11. What is the minimum frequency of DPM monitoring under normal conditions?
A) Weekly
B) Monthly
C) Quarterly (3 months)
D) 6 months
E) Yearly

✅ Answer: C
📘 Solution: Monitoring required at least once every 3 months.

Q12. If DPM exceeds 50% of the limit, monitoring must be done every:
A) 7 days
B) 15 days
C) Monthly
D) 3 months
E) 6 months

✅ Answer: C
📘 Solution: >50% → monthly monitoring.

Q13. If DPM exceeds 75% of the limit, monitoring must be done every:
A) 7 days
B) 15 days
C) 30 days
D) 60 days
E) 90 days

✅ Answer: B
📘 Solution: >75% → monitoring every 15 days.

Q14. Which sampling method is prescribed for DPM monitoring?
A) Gravimetric method
B) NIOSH 5040 (EC analysis)
C) Infrared absorption
D) Gas chromatography
E) Laser photometry

✅ Answer: C
📘 Solution: Diesel operation must be suspended until compliance achieved.

Q17. Which pollutant is the main indicator used for measuring diesel exhaust hazard?
A) Carbon monoxide (CO)
B) Oxides of nitrogen (NOx)
C) Elemental Carbon (EC)
D) Carbon dioxide (CO₂)
E) Hydrocarbons

✅ Answer: C
📘 Solution: DGMS uses EC as proxy for DPM monitoring.

Q18. Which system in diesel engines traps particulates effectively?
A) Turbocharger
B) Ceramic filter / scrubber
C) Air inlet filter
D) Intercooler
E) Fuel injector

✅ Answer: B
📘 Solution: Diesel Particulate Filters (DPF) or scrubbers capture particulates.

Q19. What is the maximum sulphur content allowed in diesel fuel for underground mining?
A) 0.1%
B) 0.075%
C) 0.05%
D) 0.5%
E) 1.0%

✅ Answer: C
📘 Solution: Fuel must be low sulphur (<0.05%).

Q20. Which health test is most important for workers exposed to diesel emissions?
A) ECG
B) Blood test
C) Spirometry (lung function test)
D) Eye test
E) Hearing test

✅ Answer: C
📘 Solution: Diesel exposure → lung impact → spirometry is critical.

Q21. Which PPE is recommended if DPM levels approach the permissible limit?
A) Ear plugs
B) Safety boots
C) Respiratory mask with P3 filter
D) Welding goggles
E) Safety helmet only

✅ Answer: E
📘 Solution: EC is chosen as a reliable marker of DPM.

Q24. Refuelling of diesel equipment underground must be done:
A) Anywhere in mine roadways
B) Only at designated refuelling bays with fire protection
C) Near working face
D) In explosive magazines
E) In workshops only

✅ Answer: C
📘 Solution: Core aim = Health & Safety by regulating DPM & ventilation.