Code of practice for safety precautions to be taken when entering a sewerage system

IS 11972: Scope & Key Specifications Summary

Scope:
IS 11972:1987 provides safety precautions for personnel entering sewerage systems, focusing on occupational hazards such as physical injury, chemical exposure, infections, toxic gases, and oxygen deficiency.

Key Points from Clause 2.1.1 and Appendix A

• Medical Examination:
  Employees must be medically re-examined at reasonable intervals considering age and duties.

• Selection of Sewermen:
  Guidance is provided for selecting personnel for sewer operations, emphasizing safety and health.

• Occupational Hazards:
  Includes risks from physical injury, chemical/radioactive wastes, pathogens, explosive/noxious vapors, and oxygen deficiency.

• Safety Equipment & Training:
  Use of appropriate safety gear and thorough training on equipment and hazards is mandatory.

International System of Units (SI) Used in IS 11972

Summary Diagram: Safety Precautions Workflow

flowchart TD
    A[Personnel Selection] --> B[Medical Examination]
    B --> C[Training on Safety & Equipment]
    C --> D[Use of Safety Gear]
    D --> E[Entry into Sewerage System]
    E --> F[Continuous Monitoring & Re-examination]

Practical Notes

• This code is a Code of Practice, not a design standard.
• It complements other IS codes by emphasizing health and safety.
• Follow local regulations and use this as a minimum safety guideline.

For detailed procedures and equipment specifications, refer to the full IS 11972 document.

IS 11972: Selection of Sewermen – Key Points

1. General Guidance (Clause 2.2 & Appendix A)

• Sewermen selection depends on type of duties:
  • Duties not requiring entry into confined spaces (Appendix A-1)
  • Duties requiring entry into confined spaces (Table A-2, Clause 2.1.1)
• Medical examination required at intervals based on age and duties (A-2.1.1).

2. Medical & Safety Requirements

• Periodic medical check-ups ensure fitness for hazardous sewer work.
• Safe system of work must be followed as per Clause 1.1.

3. Units & Symbols (SI Units)

4. Selection Criteria Summary

• Skill & Experience: Based on duty type.
• Health Status: Medical re-examination intervals.
• Training: For confined space entry and safety procedures.

flowchart TD
    A[Start: Identify Duty Type] --> B{Does duty require entry into confined space?}
    B -- No --> C[Select sewermen per Appendix A-1]
    B -- Yes --> D[Follow Table A-2 requirements]
    D --> E[Medical Examination]
    C --> E
    E --> F[Training & Safety Procedures]
    F --> G[Deploy Sewermen]

For detailed tables and exact medical criteria, refer to Appendix A and Table A-2 in IS 11972.

IS 11972: Precautions Against Gas Hazards in Sewers

Key Safety Precautions (Clause 3.1)

• No smoking/open flames; guard against sparks.
• Warning signs must be erected.
• Use safety gas-proof electric lighting or mirrors.
• Test atmosphere for noxious gases & oxygen deficiency; agitate scum to release trapped gases.
• If safe, enter with safety belt and at least two men at top.
• Repeat gas tests every 3 minutes during work.
• If hazardous gases persist, use hose masks, non-sparking tools, and permissible safety lights.
• Check ladder rungs carefully; have at least two men for rescue.
• Use portable air blowers (weatherproof, flameproof diesel motors) placed ≥2 m away on leeward side for ventilation.

Entry & Work Procedure (Clause 5.1)

Ventilation & Equipment

• Forced ventilation via blower with flexible ducting.
• Blower motor: diesel, flameproof, weatherproof, no spark plugs.
• Blower location: ≥2 m from opening, leeward side.

Summary Table: Gas Testing & Safety Gear

flowchart TD
    A[Start: Sewer Entry] --> B{Gas Test}
    B -- Safe --> C[Enter with safety belt, 2 men at top]
    B -- Hazardous --> D[Ventilate with blower]
    D --> E{Gas Test after ventilation}
    E -- Safe --> C
    E -- Hazardous -->

IS 11972: Safety Equipment for Sewerage System Entry

Key Safety Equipment (Clause 4.1)

• Safety helmet with explosion-proof cap lamp
• Safety belt and ropes
• Protective gloves
• Heavy-duty waterproof clothing (overall or heavy coat)
• Safety boots (knee/thigh length, toe protection, anti-spark studs)
• Gas masks and breathing apparatus
• Eye protectors
• Portable lighting equipment
• Non-sparking tools
• Portable air blowers
• Gas test equipment: safety candle lamps, Davy's lamps, lead acetate papers, electronic gas detectors
• First aid equipment

Safety Procedure Highlights (Clause 5.1)

1. Pre-work: Check equipment, identify hazards.
2. On-site: Mark roads, ventilate sewer openings.
3. Entry: Gas check, tie safety belt, inspect ladders.
4. Inside sewer: Gas check every 3 minutes, communication every 3 minutes.
5. Work completion: Clear tools, replace covers, inform supervisor.

Units & Definitions (SI Units)

Gas Testing & Emergency

• Use safety candle lamps, Davy lamps, lead acetate papers, and electronic detectors.
• Continuous monitoring during entry is mandatory.

flowchart TD
    A[Pre-Work: Equipment Check] --> B[On-Site: Road Marking & Ventilation]
    B --> C[Entry: Gas Check & Safety Belt]
    C --> D[Inside Sewer: Gas & Communication Check]
    D --> E[Completion: Clear & Inform Supervisor]

Summary: IS 11972 mandates comprehensive protective gear, strict entry procedures, and continuous gas monitoring to ensure sewer worker safety. Use explosion-proof and non-sparking equipment, and follow stepwise safety protocols strictly

IS 11972: Procedure for Working in a Sewer – Key Points

Safety Equipment (Clause 4.1)

• Safety helmet with explosion-proof cap lamp
• Safety belt & rope
• Protective gloves & waterproof heavy-duty clothing
• Knee/thigh-length safety boots with toe protection and anti-spark studs
• Gas masks, breathing apparatus, and eye protectors
• Portable lighting and non-sparking tools
• Portable air blowers and gas test equipment (safety lamps, electronic detectors)
• First aid kit

Stepwise Procedure (Clause 5.1)

Gas Emergency

• Always test gas before entry; if gas presence is doubtful, do not enter.
• Use gas detectors or safety lamps continuously.

Safety Monitoring Flowchart

flowchart TD
    A[Prepare Equipment & Check Hazards] --> B[Set Up Site & Ventilate]
    B --> C[Gas Test & Safety Checks]
    C --> |Safe| D[Enter Sewer with Safety Belt & Rope]
    C --> |Unsafe| E[Do Not Enter]
    D --> F[Work with Gas Checks Every 3 mins]
    F --> G[Complete Work & Remove Tools]
    G --> H[Replace Covers & Clear Site]
    H --> I[Inform Supervisor & Wash Hands]

Note: Always follow the minimum ventilation and gas testing requirements to prevent accidents in confined sewer spaces.

IS 11972: Gas Emergency Key Points

Safety Steps (Clause 5.1)

• Before Leaving Depot: Check safety gear; identify hazards.
• On Arrival: Set road markings; ventilate sewer system (working manhole + upstream manhole).
• Entry: Test gas; use safety belts/ropes; keep emergency equipment nearby.
• Inside Sewer: Check gas every 3 minutes; maintain communication between topmen and workers.
• Completion: Ensure tools removed; replace covers; clear site; inform supervisor.

Gas Emergency (Clause 6.1)

• Immediate Action: Put on breathing apparatus (escape sets) and raise alarm.

First Aid for Gas Victim (Clause 6.4)

• Move victim to fresh air immediately.
• Apply artificial respiration with oxygen if available; else mouth-to-mouth.
• Keep victim lying down; await ambulance.

Relevant Units (SI Units Table)

Summary Flowchart for Gas Emergency:

flowchart TD
    A[Gas Emergency Detected] --> B[Put on Breathing Apparatus]
    B --> C[Raise Alarm]
    C --> D[Evacuate Area]
    D --> E[Provide First Aid]
    E --> F[Call Ambulance]

Note: Always follow continuous gas monitoring and communication protocols as per IS 11972 for confined space entry.

IS 11972: Guidance for Selection of Sewermen

Key Points from Clause 2.2 & Appendix A

• Selection depends on duties: Sewermen are selected based on whether duties require entry into confined spaces or not.
• Medical examination: For duties involving confined space entry, periodic medical re-examination is mandatory considering age and job nature (Clause 2.1.1).
• Safe system of work: The standard emphasizes safe working practices for sewerage operations.

Summary Table: Sewermen Selection Criteria (Simplified)

Important Units & Definitions (SI Units)

Recommendations

• Use Appendix A for detailed duty-wise guidance.
• Ensure medical fitness for confined space duties.
• Provide adequate training based on duty type.
• Follow safe work practices as per IS 11972.

flowchart TD
    A[Selection of Sewermen]
    A --> B{Duty Type}
    B --> C[No Confined Space Entry]
    B --> D[Confined Space Entry]
    C --> E[Basic Safety Training]
    D --> F[Medical Exam + Confined Space Training]

This concise framework ensures safe and efficient sewerage operations per IS 11972.