---

📘 DGMS (Tech.)(S&T) Circular No. 02 of 2025 Issued: April 2025
Subject: 👉 Minimum Air Quantity at Continuous Miner (CM) & Longwall Panels

---

🔹 1. Why This Circular Was Needed ❓

• ⚠️ Old standard (6 m³/min/person OR 2.5 m³/min/tonne) was not sufficient in mass production panels (MPP).
• 🚧 Issues observed:
• 🌫️ Dust accumulation at LVC
• 🌡️ High heat & humidity → worker stress
• ⛔ Poor air distribution due to long panel resistance
• 💥 Methane layering in degree-II seams
• 🔥 Risk of spontaneous heating
• 🎯 Goal: Update ventilation norms for mechanized panels.

---

🔹 2. Legal Background 📜

• Based on Regulation 153 of CMR, 2017.
• Statutory minimum:
• 👷 6 m³/min per person (largest shift)
• ⛏️ 2.5 m³/min per tonne daily output
• ➕ Circular adds velocity-based norms for CM & PSLW.

---

🔹 3. Specific Provisions 📝 

  ✅ A. Continuous Miner (CM) Panels

• Degree-I seams: 0.5 m/s 🌬️
• Degree-II seams: 0.75 m/s 🌬️
• Formula:

Q=A×VQ = A \times V (A = cross-sectional area, V = velocity)

• 🌡️ DBT–WBT difference ≥ 2 °C

---

✅ B. Power Support Longwall (PSLW) Panels

• Required velocity = 3.0 m/s 💨
• 💡 Reason: Large face length + high heat & gas from shearer, AFC, supports

---

✅ C. Final Rule ⚖️

• Compare:
  1️⃣ Statutory (man/tonne-based)
  2️⃣ Circular (velocity-based)
• ✔️ Adopt whichever is higher

---

🔹 4. Research Basis 🔬

• 📌 CMPDIL Project: “Requirement of Air in Mass Production Technology”
• Findings:
• Statutory air → ❌ inadequate in CM/PSLW
• CM → dust & gas at LVC even with statutory air
• PSLW → required high face velocity (3 m/s)
• 🏭 Workshop at Jhanjra Project (ECL) with DGMS + experts

---

🔹 5. Implications for Mines 🏗️

• ⚡ Upgrade main & booster fans
• 🔄 Recalculate panel-wise air quantity
• 📊 Monitor DBT & WBT at LVC
• 🛡️ Integrate into ventilation & safety plans

---

🔹 6. Exam-Oriented Usage 🎯 📖 Written Exam:

• “As per DGMS Circular 02/2025, CM panels require 0.5–0.75 m/s, PSLW panels 3 m/s, whichever is higher than statutory minimum.”

📊 Numerical Example:

• CM panel, area = 12 m², degree-II seam
• Q = 12 × 0.75 = 9 m³/s = 540 m³/min
• Compare with statutory → take higher.

🎙️ Viva Questions:

• Why DBT–WBT ≥ 2 °C?
• Why PSLW needs 3 m/s velocity?
• How does CMPDIL research support this circular?

---

🔹 7. Quick Reference Table 📋

Panel Type	Degree	Velocity 🌬️	Formula	Extra Condition
CM Panel	I	0.5 m/s	Q = A × V	DBT–WBT ≥ 2 °C
CM Panel	II	0.75 m/s	Q = A × V	DBT–WBT ≥ 2 °C
PSLW Panel	Any	3.0 m/s	Q = A × V	Full face span

---

🔹 8. Key Takeaways 🏆

1. 📘 Circular 02/2025 = milestone in ventilation planning.
2. 🔢 Velocity norms supplement man/tonnage-based norms.
3. 🌫️ Controls dust, 💥 methane, 🌡️ heat, 💧 humidity.
4. 📝 Must be quoted in written answers & viva.

---

📝 MCQs on DGMS (Tech.)(S&T) Circular No. 02 of 2025

---

Q1. According to DGMS Circular No. 02/2025, the minimum statutory air quantity at the Last Ventilation Connection (LVC) is:
A) 4 m³/min per man
B) 6 m³/min per man
C) 8 m³/min per man
D) 10 m³/min per man
E) None of the above 

✅ Answer: B

📘 Solution: CMR 2017 Reg. 153 requires 6 m³/min per man. Circular 02/2025 reinforces this.

---

Q2. What is the alternative statutory requirement for air quantity besides per man basis?
A) 1.5 m³/min per tonne of output
B) 2.0 m³/min per tonne of output
C) 2.5 m³/min per tonne of output
D) 3.0 m³/min per tonne of output
E) None of the above 

✅ Answer: C

📘 Solution: The rule is 6 m³/min per man OR 2.5 m³/min per tonne, whichever is higher.

---

Q3. For a Continuous Miner panel in a Degree-I gassy seam, the minimum velocity required at LVC is:
A) 0.25 m/s
B) 0.5 m/s
C) 0.75 m/s
D) 1.0 m/s
E) 1.5 m/s 

✅ Answer: B

📘 Solution: DGMS Circular prescribes 0.5 m/s for Degree-I seams.

---

Q4. For a Continuous Miner panel in a Degree-II gassy seam, the required velocity at LVC is:
A) 0.5 m/s
B) 0.6 m/s
C) 0.75 m/s
D) 1.0 m/s
E) 1.25 m/s 

✅ Answer: C

📘 Solution: 0.75 m/s is mandated for Degree-II CM panels.

---

Q5. For PSLW (Power Support Longwall) panels, what is the minimum velocity across the full face?
A) 1.0 m/s
B) 1.5 m/s
C) 2.0 m/s
D) 3.0 m/s
E) 4.0 m/s 

✅ Answer: D

📘 Solution: PSLW requires 3.0 m/s due to large span and heavy mechanization.

---

Q6. The temperature requirement in Circular 02/2025 prescribes a minimum difference of ____ between DBT and WBT.
A) 1 °C
B) 2 °C
C) 3 °C
D) 4 °C
E) 5 °C 

✅ Answer: B

📘 Solution: Circular mandates ≥ 2 °C difference between DBT & WBT for comfort & safety.

---

Q7. The formula for calculating required air quantity in CM and PSLW panels is:
A) Q = A × V
B) Q = P × V
C) Q = A ÷ V
D) Q = V² × A
E) None of the above 

✅ Answer: A

📘 Solution: Airflow = Cross-sectional area × Velocity at LVC.

---

Q8. Which organization conducted R&D leading to Circular 02/2025?
A) DGMS HQ
B) CMPDIL
C) SCCL
D) NIRM
E) IIT-ISM 

✅ Answer: B

📘 Solution: CMPDIL studied air requirement in MPT → basis for circular.

---

Q9. The workshop presenting findings of this circular was held at:
A) Jharia Project
B) Jhanjra Project
C) Talcher Mines
D) Singareni Mines
E) Khetri Project 

✅ Answer: B

📘 Solution: CMPDIL’s results were discussed at Jhanjra Project (ECL).

---

Q10. Why was 3 m/s chosen as the velocity for PSLW panels?
A) To reduce dust only
B) To sweep methane and heat across large face
C) To improve productivity
D) For compliance with international standards
E) None of these 

✅ Answer: B

📘 Solution: 3 m/s ensures methane dilution, dust control & heat removal in longwall faces.

---

Q11. If a CM panel has a cross-section of 10 m² in a Degree-II seam, what is the minimum air required at LVC (as per Circular 02/2025)?
A) 500 m³/min
B) 450 m³/min
C) 600 m³/min
D) 750 m³/min
E) None 

✅ Answer: A

📘 Solution:
Q = A × V = 10 × 0.75 = 7.5 m³/s = 450 m³/min.
But must compare with statutory; if 6 m³/min/man is higher, that applies.

---

Q12. Which parameter was specifically added in Circular 02/2025 for thermal comfort?
A) Dry Bulb Temperature (DBT) alone
B) Wet Bulb Temperature (WBT) alone
C) DBT–WBT difference ≥ 2 °C
D) Relative humidity < 60%
E) None 

✅ Answer: C

📘 Solution: DBT–WBT ≥ 2 °C must be maintained.

---

Q13. The problem of spontaneous heating in CM panels is mainly due to:
A) High air velocity
B) Poor ventilation pressure & dust concentration
C) Excess cooling
D) Low methane emission
E) None 

✅ Answer: B

📘 Solution: Low velocity + high resistance → dust pockets → heat build-up → spontaneous heating.

---

Q14. Which of the following is NOT a reason for issuing Circular 02/2025?
A) Increase in MPP production
B) High dust load in CM panels
C) Need for higher face velocity in PSLW
D) Reduction of coal royalty
E) Heat accumulation at LVC 

✅ Answer: D

📘 Solution: The circular was issued for ventilation & safety, not economics.

---

Q15. What is the guiding principle for selecting final air requirement in CM/PSLW panels?
A) Always man-based only
B) Always tonnage-based only
C) Always velocity-based only
D) Whichever is higher between statutory & velocity-based norms
E) None 

✅ Answer: D

📘 Solution: Rule: Whichever is higher (statutory vs. velocity-based).

---

---

Q16. What is the primary purpose of maintaining DBT–WBT difference in mines?
A) To improve lighting
B) To ensure thermal comfort and reduce heat stress
C) To reduce methane emission
D) To control coal dust size
E) To increase humidity 

✅ Answer: B

📘 Solution: A difference of ≥2 °C ensures workers don’t suffer from heat stress and maintains thermal comfort.

---

Q17. Which gas is most critical in Degree-II gassy seams, influencing the 0.75 m/s velocity norm?
A) Carbon dioxide (CO₂)
B) Methane (CH₄)
C) Carbon monoxide (CO)
D) Hydrogen sulphide (H₂S)
E) Nitrogen (N₂) 

✅ Answer: B

📘 Solution: Methane accumulation risk in degree-II seams justifies the higher velocity of 0.75 m/s.

---

Q18. In which type of mining panels does Circular 02/2025 NOT specifically prescribe velocity norms?
A) Continuous Miner panels
B) PSLW panels
C) Conventional Bord & Pillar panels
D) Mass Production panels
E) Longwall panels 

✅ Answer: C

📘 Solution: The circular specifically targets CM & PSLW panels, not conventional bord & pillar.

---

Q19. If a PSLW panel has cross-sectional area = 15 m², what is the minimum airflow required?
A) 600 m³/min
B) 900 m³/min
C) 1800 m³/min
D) 2700 m³/min
E) None 

✅ Answer: C

📘 Solution:
Q = A × V = 15 × 3 = 45 m³/s = 2700 m³/min.

---

Q20. Which of the following is a direct hazard prevented by adopting Circular 02/2025 norms?
A) Rock bursts
B) Spontaneous heating & methane layering
C) Strata collapse
D) Water inrush
E) Roof fall 

✅ Answer: B

📘 Solution: Adequate airflow reduces dust/heat pockets and prevents spontaneous heating and methane layering.

---

Q21. Which parameter is common to both CM and PSLW panel ventilation norms in this circular?
A) Cross-sectional area considered
B) Face support density
C) DBT–WBT difference
D) Degree of gassiness always same
E) Fan efficiency 

✅ Answer: A

📘 Solution: For both CM & PSLW, calculation is based on Q = A × V.

---

Q22. The term LVC in Circular 02/2025 refers to:
A) Last Ventilation Checkpoint
B) Last Ventilation Connection
C) Low Velocity Control
D) Local Ventilation Chamber
E) Longwall Ventilation Channel 

✅ Answer: B

📘 Solution: LVC = Last Ventilation Connection, where minimum air quantity must be ensured.

---

Q23. In ventilation planning, which is TRUE according to Circular 02/2025?
A) Man-based norms always dominate
B) Tonnage-based norms always dominate
C) Velocity-based norms always dominate
D) Higher of statutory vs velocity-based norms applies
E) Lowest value can be accepted 

✅ Answer: D

📘 Solution: Rule = Whichever is higher (statutory vs velocity-based).

---

Q24. What was the venue of the CMPDIL workshop where findings of Circular 02/2025 were discussed?
A) Singareni Collieries
B) Talcher Project
C) Jhanjra Project (ECL)
D) Korba Mines
E) Khetri Mines 

✅ Answer: C

📘 Solution: Findings were presented at Jhanjra Project of ECL.

---

Q25. Which of the following best summarizes Circular 02/2025?
A) Safety guidelines for dumpers
B) Water danger precautions
C) Minimum air quantity norms for CM & PSLW panels
D) Explosives storage rules
E) Rescue equipment standards 

✅ Answer: C

📘 Solution: Circular 02/2025 deals with air quantity/velocity norms for CM & PSLW panels in mass production technology.

---

---

---