DGMS Circular on Dust Suppression & Environmental Measures

🔹DGMS Circular on Dust Suppression & Environmental Measures – Coal Mine Safety Notes
Detailed exam-ready notes on DGMS guidelines for dust suppression in coal mines. Covers sources of dust, health hazards, dust control measures, and DGMS environmental guidelines with FAQs for DGMS exams.

🔹 Introduction Airborne dust in coal mines is one of the most critical hazards leading to long-term occupational diseases such as pneumoconiosis, silicosis, and chronic bronchitis. To minimize health risks and accidents, DGMS has issued specific circulars and technical guidelines on dust suppression and environmental measures. These rules are binding under the Coal Mines Regulations (CMR 2017) and the Mines Act, 1952. This blog provides exam-focused notes on the circular, with pointer-wise explanations to help candidates prepare for DGMS Manager, Overman, Mining Sirdar, and Surveyor examinations.

🔹 Detailed Notes (Exam-Oriented) 1. Sources of Dust in Coal Mines

Drilling operations (coal & stone)
Blasting of coal/overburden
Loading & unloading operations
Transportation (belt conveyors, roadways, haulage)
Cutting, crushing, screening & handling
Movement of workers and equipment in dry workings

2. Health Hazards of Dust

Pneumoconiosis – caused by inhaling coal dust
Silicosis – caused by inhaling free silica dust (from stone/overburden)
Chronic Bronchitis & Asthma – long-term effects
Eye irritation & reduced visibility in workings
Increased risk of explosibility (coal dust explosions when mixed with air)

3. DGMS Dust Suppression Measures

Watering arrangements in roadways, haul roads, coal faces
Stone dusting in underground coal mines (to reduce explosibility)
Wet drilling mandatory in coal & stone drilling
Dust extractors/collectors on drills and cutting machines
Chemical treatment for long-term suppression (salts, hygroscopic chemicals)
Enclosed cabins for operators of drills/loaders
Personal protective equipment (PPE): Dust respirators, masks

4. Environmental Measures

Mechanical Ventilation: Proper air circulation to dilute & remove dust
Water Sprays: Fixed & mobile sprays at transfer points
Chemical Suppressants: Magnesium chloride, calcium chloride, surfactants
Green Belt Development: Plantation to trap airborne dust in surface mines
Dust Extraction Systems: Bag filters, cyclones, scrubbers at crushing/screening plants
Conveyor belt covers & transfer point hoods

5. Monitoring & Standards

Dust levels measured using Personal Dust Samplers
Permissible Limit (as per DGMS & ILO):
- Respirable Coal Dust: 3 mg/m³ (8-hour TWA)
- Free Silica Dust: <10% of dust concentration
Regular monitoring at workplaces (face, return airway, transfer points)
Medical examination of workers under Mines Rules, 1955 (pre-employment + periodical)

6. Responsibilities Mine Management must ensure:

Implementation of DGMS circulars
Installation & maintenance of dust suppression systems
Training of workers in dust hazards & protective equipment
Regular reporting of dust sampling results to DGMS

Workers must:

Use protective equipment properly
Follow safe work practices
Report failures in dust suppression arrangements

🔹 Conclusion Dust suppression is a mandatory safety requirement under DGMS circulars and plays a vital role in safeguarding the health of miners and preventing accidents like dust explosions. For exam purposes, candidates must focus on:

Sources of dust
Health effects
DGMS-prescribed measures
Permissible limits & monitoring methods
Exam-Oriented MCQs on

DGMS Circular on Dust Suppression & Environmental Measures – Control of Airborne Dust in Coal Mines

1. The main disease caused by coal dust exposure is:

A) Tuberculosis
B) Pneumoconiosis
C) Bronchitis
D) Silicosis
E) Asthma

✅ Answer: B) Pneumoconiosis
💡 Explanation: Inhalation of coal dust leads to accumulation in the lungs causing pneumoconiosis.

2. The disease specifically caused by free silica dust is:

A) Pneumoconiosis
B) Asthma
C) Silicosis
D) Fibrosis
E) Emphysema

✅ Answer: C) Silicosis
💡 Explanation: Free crystalline silica particles damage lung tissue, leading to silicosis.

3. Permissible limit of respirable coal dust in India (8-hr TWA) is:

A) 5 mg/m³
B) 3 mg/m³
C) 10 mg/m³
D) 1 mg/m³
E) 8 mg/m³

✅ Answer: B) 3 mg/m³
💡 Explanation: DGMS has fixed 3 mg/m³ as the permissible time-weighted average for coal dust.

4. Which dust is more harmful due to fibrogenic property?

A) Coal dust
B) Free silica dust
C) Iron dust
D) Gypsum dust
E) Limestone dust

✅ Answer: B) Free silica dust
💡 Explanation: Silica dust has a higher fibrogenic property, leading to silicosis.

5. Wet drilling in coal mines is made mandatory to:

A) Reduce noise
B) Reduce dust generation
C) Increase drilling speed
D) Save electricity
E) Reduce tool wear

✅ Answer: B) Reduce dust generation
💡 Explanation: Water injection during drilling prevents dust from becoming airborne.

6. Which method is used in underground coal mines to prevent dust explosions?

A) Wet drilling
B) Ventilation
C) Stone dusting
D) Water spraying
E) PPE use

✅ Answer: C) Stone dusting
💡 Explanation: Stone dust dilutes coal dust and prevents explosibility.

7. Commonly used chemical for dust suppression in mines:

A) Sodium chloride
B) Magnesium chloride
C) Potassium nitrate
D) Sodium carbonate
E) Calcium sulfate

✅ Answer: B) Magnesium chloride
💡 Explanation: Hygroscopic salts like MgCl₂ retain moisture, keeping dust settled.

8. Personal protective equipment for dust exposure is:

A) Helmets
B) Safety boots
C) Dust respirators
D) Ear plugs
E) Goggles

✅ Answer: C) Dust respirators
💡 Explanation: Dust masks/respirators filter airborne dust particles.

9. Stone dusting is effective because it:

A) Increases coal cutting speed
B) Absorbs heat of explosion
C) Dilutes coal dust
D) Improves visibility
E) Neutralizes methane

✅ Answer: C) Dilutes coal dust
💡 Explanation: Stone dust reduces the explosibility of coal dust by inerting it.

10. Which is NOT a source of dust in mines?

A) Blasting
B) Coal cutting
C) Wet drilling
D) Haul roads
E) Conveyors

✅ Answer: C) Wet drilling
💡 Explanation: Wet drilling prevents dust instead of generating it.

11. Main instrument for dust sampling in coal mines:

A) Barometer
B) Hygrometer
C) Personal Dust Sampler
D) Gas Chromatograph
E) Anemometer

✅ Answer: C) Personal Dust Sampler
💡 Explanation: PDS measures respirable dust concentration in the mine atmosphere.

12. Which regulation requires medical examination of miners exposed to dust?

A) CMR 2017
B) Mines Rules 1955
C) MMR 1961
D) Factory Act 1948
E) DGMS Tech Circular

✅ Answer: B) Mines Rules 1955
💡 Explanation: Mines Rules, 1955 mandates pre-employment and periodic medical exams.

13. Long-term exposure to coal dust leads to:

A) Pneumoconiosis
B) Asbestosis
C) Byssinosis
D) Silicosis
E) Black lung disease

✅ Answer: A) Pneumoconiosis (Black lung disease)
💡 Explanation: Coal workers’ pneumoconiosis is also called black lung disease.

14. Maximum permissible percentage of free silica in coal mine dust is:

A) 10%
B) 20%
C) 5%
D) 15%
E) 25%

✅ Answer: A) 10%
💡 Explanation: If silica >10%, stricter dust control measures are mandatory.

15. Which of the following is an engineering control for dust suppression?

A) Dust masks
B) Wet drilling
C) Medical checkup
D) Worker rotation
E) Training

✅ Answer: B) Wet drilling
💡 Explanation: Engineering control directly reduces dust at source.

16. Dust explosions in coal mines can be prevented by:

A) Using PPE
B) Increasing ventilation only
C) Diluting coal dust with inert stone dust
D) Sprinkling fuel oil
E) None

✅ Answer: C) Diluting coal dust with inert stone dust
💡 Explanation: Stone dusting prevents coal dust from igniting/exploding.

17. Which environmental measure is used for surface coal mines?

A) Stone dusting
B) Green belt development
C) Flameproof equipment
D) Methane drainage
E) Rock bolting

✅ Answer: B) Green belt development
💡 Explanation: Plantation around mines traps airborne dust.

18. Dust level monitoring should be done:

A) Daily
B) Weekly
C) Monthly
D) Quarterly
E) Yearly

✅ Answer: C) Monthly (minimum as per DGMS guidelines)
💡 Explanation: Dust monitoring frequency is decided by DGMS based on risk assessment.

19. Which organ is primarily affected by mine dust?

A) Heart
B) Kidneys
C) Lungs
D) Liver
E) Brain

✅ Answer: C) Lungs
💡 Explanation: Dust inhalation affects lungs leading to fibrosis.

20. Stone dust used in mines must have:

A) High moisture content
B) Non-combustible property
C) Magnetic property
D) Carbon content >20%
E) None of the above

✅ Answer: B) Non-combustible property
💡 Explanation: Inert stone dust reduces coal dust explosibility.

21. Most effective dust control is:

A) PPE
B) Administrative control
C) Engineering control
D) Medical examination
E) Worker awareness

✅ Answer: C) Engineering control
💡 Explanation: Controlling dust at source is most effective.

22. Chronic dust exposure leads to:

A) Acute poisoning
B) Long latency occupational disease
C) Food poisoning
D) Skin rashes
E) None

✅ Answer: B) Long latency occupational disease
💡 Explanation: Diseases like silicosis and pneumoconiosis develop slowly over years.

23. Which is a DGMS-recommended practice for haul roads?

A) Compaction only
B) Frequent water spraying
C) Only chemical treatment
D) Oil sprinkling
E) None

✅ Answer: B) Frequent water spraying
💡 Explanation: Watering is the simplest and most common haul road dust suppression method.

24. A dust explosion requires:

A) Methane + coal dust
B) Heat + dust + oxygen
C) Dust + nitrogen
D) Water + coal dust
E) Only oxygen

✅ Answer: B) Heat + dust + oxygen
💡 Explanation: Dust explosions need a combustible dust-air mixture + ignition source.

25. DGMS requires reporting of dust monitoring results:

A) To mine workers only
B) To state government
C) To DGMS authorities
D) To trade unions
E) None

✅ Answer: C) To DGMS authorities
💡 Explanation: Management must submit monitoring results to DGMS regularly.

Online Mining Exam
India's 1st Online Mining Academy Prepare for DGMS 1st Class & 2nd Class Mining Manager Exams (Coal & Metal, Restricted & Unrestricted)