Introduction to Confined Space
A confined space is an area not designed for continuous occupancy, with limited entry/exit, and potential for hazardous atmosphere or physical risks.
Definition of Confined Space
- Limited or restricted means of entry and exit
- Not meant for regular human occupancy
- Large enough for a person to enter and work
- Can contain actual or potential hazards
Examples in Industry
- Storage tanks
- Silos and hoppers
- Boilers and furnaces
- Reactors and vessels
- Sewers and manholes
- Pipelines and ducts
- Pits, sumps, and trenches
- Cargo holds and underground vaults
Why Confined Spaces Are Dangerous
- Oxygen deficiency or enrichment
- Presence of toxic gases or vapors
- Flammable or explosive atmosphere
- Poor ventilation
- Risk of engulfment or entrapment
- Limited escape routes
- Heat stress
- Difficulty in rescue operations
Types of Confined Spaces
1. Permit-Required Confined Space
Has hazardous atmosphere (toxic, flammable, low/high oxygen)
Risk of engulfment (liquid, grain, powder, sludge)
Internal shape can trap or suffocate a person
Any other serious safety or health risk
Entry allowed only with approved permit and controls
2. Non-Permit Confined Space
No hazardous atmosphere
No engulfment risk
No serious safety or health hazards
Safer to enter but still needs basic precautions
3. Open Confined Space
Opening is large or fully open
Easier natural ventilation
Examples: open pits, open tanks, sumps
4. Enclosed Confined Space
Small or restricted openings
Poor natural ventilation
Higher risk of gas buildup
Examples: reactors, boilers, manholes, silos
Confined Space Risk Assessment
Job Hazard Analysis (JHA)
Step-by-step study of the job before entry
Identifies what can go wrong at each step
Used to plan safe work methods
Identifying Hazards
Checking for toxic, flammable, or low-oxygen atmosphere
Finding chemical residues, pressure, heat, moving parts
Looking for biological, electrical, and physical risks
Risk Rating
Judging how severe the harm can be (low, medium, high)
Checking how likely the hazard can occur
Helps decide level of control needed
Control Measures
Removing the hazard (cleaning, draining, isolating)
Engineering controls (ventilation, gas detectors)
Administrative controls (permit, training, supervision)
PPE (respirator, harness, gloves, SCBA)
Isolation & Energy Control
Lockout/Tagout (LOTO)
Physically locking energy sources to prevent accidental start-up
Tag shows who locked it and why
Used for electrical, mechanical, hydraulic, pneumatic, and steam systems
Blanking & Blinding
Inserting a positive blind (Tail blind - SS, PTFE etc) in pipelines
Completely blocks flow of chemicals, gas, or steam
Most reliable method of isolation
Valve Isolation
Closing and locking valves to stop flow of liquid or gas
Often combined with double block and bleed
Must be verified by pressure release and testing
Electrical Isolation
Switching off, locking, and testing circuits for zero energy
Prevents electric shock and accidental equipment start
Includes MCCs, panels, and local switches
Mechanical Isolation
Physically disconnecting or blocking moving parts
Prevents rotation, movement, or falling parts
Used for agitators, mixers, conveyors, pumps
Ventilation & Purging
Natural vs Forced Ventilation
Natural ventilation: Uses natural air flow through openings; suitable only for low-risk spaces
Forced ventilation: Uses blowers or fans to push fresh air and remove gases; required for toxic, flammable, or low-oxygen areas
Purging Methods
Replacing hazardous gases or vapors with fresh air or inert gas
Used to remove toxic, flammable, or reactive atmospheres
Common methods: air purging, nitrogen purging, steam purging (as per process need)
Always followed by gas testing before entry
Air Changes Calculation
Measures how many times air inside the space is replaced per hour
Ensures enough fresh air to dilute or remove harmful gases
Higher hazard = more air changes required
Verified by gas testing, not only by time
Atmospheric Testing
Why Gas Testing Is Required
To check if air is safe for breathing
To detect toxic, flammable, or oxygen-deficient conditions
To prevent fire, explosion, and poisoning
Types of Gas Detectors
Single gas detector: Measures one specific gas
Multi-gas detector: Measures oxygen, flammable gases, and toxic gases together
Fixed detectors: Installed permanently in vessels or areas
Portable detectors: Handheld for entry checks
Oxygen, LEL, Toxic Gas Limits
Oxygen: Safe range 19.5% – 23.5%
LEL: Must be below 10% for safe entry
Toxic gases: Must be below permissible exposure limits (PEL/TLV)
Pre-Entry Testing
Done before anyone enters the space
Testing at top, middle, and bottom levels
Confirms space is safe to enter
Continuous Monitoring
Ongoing gas testing during work
Detects sudden gas leaks or oxygen changes
Alerts workers before conditions become dangerous
Hazards in Confined Spaces
Confined Space Hazards with Mitigation
Oxygen deficiency: Low oxygen due to nitrogen purging, rusting, or gas displacement
Mitigation: O₂ testing, forced ventilation, continuous monitoring, SCBA if needed
Nitrogen displacement: Oxygen pushed out, suffocation
Mitigation: Isolate N₂ lines, purge with air, oxygen alarms, permit control
Oxygen enrichment: High oxygen increasing fire and explosion risk
Mitigation: Control oxygen sources, no oil/grease, fire-safe tools
Toxic gases and vapors: Poisonous fumes from chemicals, solvents, reactions
Mitigation: Gas testing, ventilation, respirator/SCBA
Flammable gases and vapors: LPG, methane, solvent vapors catching fire easily
Mitigation: LEL monitoring, grounding, ignition control
Explosive atmosphere: Gas–air mixture igniting suddenly
Mitigation: Intrinsically safe tools, continuous gas monitoring
Dust explosion: Fine powder igniting (API, starch, sugar, chemicals)
Mitigation: Dust cleaning, anti-static PPE, explosion-proof tools
Engulfment: Being buried in sludge, powder, liquid, or granules
Mitigation: Empty, isolate, barriers, standby watch
Drowning: Entry into liquid-filled tanks, pits, or sumps
Mitigation: Drain, blind lines, harness, tripod
Asphyxiation: Lack of oxygen due to gas displacement
Mitigation: O₂ monitor, ventilation, SCBA
Suffocation: Blocked airways or tight spaces preventing breathing
Mitigation: Space assessment, rescue setup
Poor ventilation: No fresh air flow, gas buildup
Mitigation: Blowers, exhaust fans
Heat stress: High temperature from reactors, steam, poor airflow
Mitigation: Cooling ventilation, hydration, rest breaks
Cold stress: Very low temperature from cryogenic or cold processes
Mitigation: Thermal PPE, time limits
High humidity: Causes discomfort, heat stress, poor breathing
Mitigation: Ventilation, hydration
Slippery surfaces: Oil, chemicals, condensate causing falls
Mitigation: Spill cleanup, anti-slip mats
Limited entry and exit: Difficult escape during emergencies
Mitigation: Rescue access, tripod, lifeline
Restricted movement: Narrow spaces causing strain and injury
Mitigation: Job planning, ergonomic tools
Poor visibility: Vapors, fumes, darkness
Mitigation: Explosion-proof lights
Low lighting: Trip, fall, wrong operation
Mitigation: Adequate lighting
Electrical hazards: Live cables, faulty tools, wet conditions
Mitigation: LOTO, insulated tools, dry area
Mechanical hazards: Agitators, mixers, pumps inside vessels
Mitigation: Full isolation, mechanical blocking
Rotating or moving parts: Crushing or entanglement risk
Mitigation: Guards, zero-energy check
Unexpected energization: Sudden start of equipment
Mitigation: LOTO, tag system
Chemical exposure: Skin, eye, or inhalation damage — Mitigation: Chemical PPE, MSDS, eyewash
Corrosive substances: Burns from acids, alkalis — Mitigation: Acid/alkali-resistant PPE
Irritant gases: CO, ammonia, chlorine causing breathing issues — Mitigation: Gas detectors, respirators
Biological hazards: Bacteria, fungi in effluent tanks — Mitigation: Disinfection, PPE
Insects, rodents, snakes: Bites and infections — Mitigation: Inspection, pest control
Fungal or bacterial growth: Respiratory infections — Mitigation: Cleaning, ventilation
Noise hazards: High noise from compressors, blowers — Mitigation: Ear protection
Vibration hazards: Fatigue and muscle injury — Mitigation: Anti-vibration tools
Structural collapse: Weak tanks, corroded walls — Mitigation: Integrity inspection
Falling objects: Tools or materials dropping from above — Mitigation: Tool lanyards, barricading
Uneven or unstable flooring: Tripping and falling — Mitigation: Leveling, marking
Sharp edges: Cuts from metal sheets, flanges — Mitigation: Deburring, gloves
Falling from height: Vertical entries, manholes — Mitigation: Harness, lifeline, tripod
Static electricity: Spark causing fire or explosion — Mitigation: Grounding, bonding
Residual chemicals: Leftover toxic or flammable material — Mitigation: Washing, neutralization
Residual pressure: Sudden release of gas or liquid — Mitigation: Venting, depressurization
Steam release: Burns and suffocation — Mitigation: Isolation, cooling
Water ingress: Flooding from lines or rain — Mitigation: Valve isolation, covers
Flooding: Sudden filling of confined area — Mitigation: Drain control, standby pump
Panic and claustrophobia: Mental stress affecting judgment — Mitigation: Pre-job briefing, trained workers
Communication failure: No signal inside tanks or pits — Mitigation: Wired radios, standby man
Delayed rescue: Difficult access for rescue team — Mitigation: Rescue plan, tripod
Inadequate emergency response: No proper plan or equipment — Mitigation: Drills, equipment readiness
Poor housekeeping: Waste causing fire, slips, trips — Mitigation: Pre-cleaning
Accumulated waste: Gas generation, blockage — Mitigation: Full cleaning
Hidden hazards: Not visible dangers inside vessels — Mitigation: Detailed inspection
Atmospheric layering: Heavy gases settling at bottom — Mitigation: Multi-level gas testing
Chemical reactions: Unexpected heat, gas, or pressure — Mitigation: Compatibility check
Decomposition gases: Toxic gases from waste or residues — Mitigation: Gas testing, ventilation
Welding fumes: Toxic metal fumes — Mitigation: Local exhaust, respirator
Solvent vapors: Fire, dizziness, poisoning — Mitigation: Explosion-proof ventilation
Poor ergonomics: Awkward posture causing injury — Mitigation: Task planning
Fatigue: Reduced alertness and mistakes — Mitigation: Rest breaks
Dehydration: Heat, sweating, poor fluid intake — Mitigation: Drinking water
Chemicals/solvent absorption through skin: Toxicity without inhalation — Mitigation: Chemical-resistant PPE
Oxygen scavenger chemicals: Removing oxygen from air — Mitigation: O₂ monitoring, SCBA
Backflow from connected lines: Unexpected flooding — Mitigation: Double isolation, blinds
Metal fume fever: Inhalation of zinc, copper fumes — Mitigation: Local exhaust, respirator
Confined Space Permit System
Purpose of Permit
To ensure all hazards are identified and controlled before entry
To confirm isolation, gas testing, ventilation, and rescue readiness
To authorize safe entry formally
When Permit Is Required
For spaces with toxic, flammable, or low-oxygen atmosphere
When there is risk of engulfment, flooding, or moving parts
For tanks, reactors, vessels, pits, sumps, and manholes
Permit Validity
Valid only for a specific job, location, and time
Automatically void if conditions change
Must be revalidated after breaks or shift change
Display and Closure of Permit
Permit must be displayed at entry point
All workers must follow permit conditions
Closed only after job completion, area cleaned, and hazards removed
Confined Space Roles & Responsibilities
Entry Supervisor
Approves and signs the confined space permit
Ensures all hazards are identified and controlled
Verifies gas testing, isolation, ventilation, and rescue readiness
Stops work if unsafe conditions arise
Authorized Entrant
Person who enters the confined space to perform the job
Follows permit conditions and safety rules
Wears required PPE and gas detector
Exits immediately if alarm sounds or conditions change
Standby Person / Attendant
Stays outside the confined space at all times
Monitors entrants and conditions continuously
Maintains communication with entrants
Initiates emergency response, does not enter for rescue
Rescue Team
Trained to rescue from confined spaces safely
Uses proper rescue equipment (tripod, winch, SCBA)
Performs non-entry or entry rescue as planned
Provides first aid until medical help arrives
Confined Space Entry Procedure
Pre-Entry Checklist
Valid confined space permit approved
All isolations completed (LOTO, blinding, valves)
Gas testing done and safe readings confirmed
Ventilation started and working
Rescue equipment ready
Standby person assigned
Tool and Equipment Checks
Tools are safe, non-sparking if required
Electrical tools are insulated and grounded
Gas detectors calibrated and working
PPE in good condition (respirator, harness, gloves, helmet)
Lighting is explosion-proof if needed
Communication Methods
Verbal communication if audible
Walkie Talkie
Hand signals or rope signals as backup
Continuous contact with standby person
Entry and Exit Procedures
Enter slowly after final gas check
Follow permit conditions strictly
Maintain communication at all times
Exit immediately if alarm sounds or conditions change
Normal exit after job completion and clearance
PPE for Confined Space
Respiratory Protection
Protects against toxic gases, vapors, and low oxygen
Types: cartridge mask, air-line respirator, SCBA
Selected based on gas type and concentration
SCBA vs Airline Respirator
SCBA: Own air supply, used in unknown or oxygen-deficient atmosphere
Airline respirator: Supplied air from outside, used in controlled conditions
SCBA is safer for high-risk and emergency situations
Harness & Lifeline
Used for vertical or difficult entries
Helps in quick rescue without entering the space
Connected to tripod or winch system
Gas Monitors
Portable detectors worn by entrant
Continuously check oxygen, flammable gases, and toxic gases
Alarm warns before conditions become dangerous
Intrinsically Safe Tools
Designed not to produce sparks or heat
Used in flammable or explosive atmospheres
Prevents fire and explosion risks
Emergency & Rescue Plan
Why Self-Rescue Is Dangerous
Person inside may be unconscious or disoriented
Toxic or low-oxygen atmosphere can kill within seconds
Panic leads to wrong decisions
Untrained rescue attempts often cause multiple fatalities
Types of Rescue
Non-entry rescue: Pulling the person out without entering using tripod, winch, lifeline
Entry rescue: Trained team enters with SCBA when non-entry is not possible
Rescue Equipment
Tripod with winch and lifeline
Full body harness
SCBA or airline respirator
Stretcher and first aid kit
Gas detectors
Explosion-proof lighting
Communication devices
Mock Drill Procedure
Simulate emergency scenario
Practice alarm activation and communication
Perform rescue using actual equipment
Provide first aid and evacuation
Review response time and mistakes
Improve the rescue plan based on learning
Confined Space First Aid & Medical Response
Gas Inhalation Response
Remove the person from the confined space to fresh air immediately
Do not enter without proper respiratory protection
Loosen tight clothing and keep the person calm
Give oxygen if trained and available
Shift to medical facility without delay
CPR Basics
Check responsiveness and breathing
Call for medical help immediately
If not breathing, start chest compressions (hard and fast, center of chest)
Give rescue breaths if trained
Continue until help arrives or the person revives
Heat Stress Management
Move the person to a cool, shaded area
Loosen PPE and clothing
Give cool drinking water if conscious
Apply cool packs to neck, armpits, and groin
Monitor breathing and pulse
Send for medical help if symptoms persist
Confined Space Legal & Standard Requirements — Key Clauses & References
1. OSHA (U.S. Standard 29 CFR 1910.146 — Permit-Required Confined Spaces)
1910.146(a): Scope—permits and procedures required for confined space entry in general industry.
1910.146(b): Definitions for confined space, entry permit, attendant, authorized entrant, etc.
1910.146(d)(1)—(3): Employer must prevent unauthorized entry, identify and evaluate hazards, and implement measures to control hazards.
(OSHA standards also include requirements for permits, training, equipment, testing, monitoring, communication, and rescue procedures.)
2. Indian Regulations (Factories Act & Model Rules under Factories Act, 1948)
Factories Act, 1948 — Section 36: No person shall enter a chamber, tank, vat, pit, pipe, flue, or similar confined space where gases, fumes, vapors, or dust pose a risk unless it has adequate egress, hazards are removed, a competent person issues a written certificate, or appropriate breathing apparatus is worn.
Model Rules (Schedule XVI): Before testing or entry, the space shall be rendered safer by cleaning, purging, forced ventilation; tests must be carried out by a competent person; training, PPE, rescue and first-aid arrangements must be provided; and entry is regulated by a permit-to-work system.
3. Occupational Safety, Health & Working Conditions Code, 2020 (India)
The Code consolidates labour safety laws and empowers rules and regulations on occupational safety and health, including confined space work standards and requirements for safe conditions, permits, training, and emergency arrangements (subject to rules to be notified).
4. International Practice & Standards
Standards such as ANSI/ASSP Z117.1 set minimum safety requirements for confined space entry, hazard evaluation, atmospheric testing, and rescue planning (referenced as global best practice).
Employer Responsibilities
Identify and classify confined spaces
Conduct hazard evaluation and atmospheric testing
Provide written permits and safe systems of work
Ensure isolation, ventilation, monitoring, and rescue arrangements
Train workers and maintain records
Worker Responsibilities
Follow permit conditions
Use required PPE and monitoring equipment
Report unsafe conditions immediately
Confined Space Accidents
1) 5 Workers Die Cleaning Sludge Tank — Kandla, Kutch (Oct 2024)
Five workers suffocated while cleaning a sludge/effluent tank at Emami Agrotech (industrial facility) in Kandla, Gujarat. All died after entering the tank and losing consciousness.
🔗 Source: The New Indian Express — https://www.newindianexpress.com/nation/2024/Oct/16/five-workers-die-due-to-asphyxiation-while-cleaning-tank-at-agrotech-firm-in-gujarat-2
2) 3 Workers Die in Ballast Tank — Tuticorin Harbour (Sep 2025)
Three workers died due to suspected asphyxiation while cleaning a ballast tank on a barge at the Old Tuticorin harbour.
🔗 Source: Times of India — https://timesofindia.indiatimes.com/city/madurai/3-choke-to-death-in-ballast-tank-at-tuticorin-harbour/articleshow/123954829.cms
3) 3 Workers Die Cleaning Sugar Mill Tank — Bijnor, Uttar Pradesh (Jul 2025)
Three workers died and one critically injured after inhaling toxic gas while cleaning a tank at Uttam Sugar Mill in Bijnor district, indicating ignored safety protocols.
🔗 Source: Business & Human Rights Resource Centre (Hindustan Times cited) — https://www.business-humanrights.org/en/latest-news/three-workers-die-one-critical-after-inhaling-toxic-gas-while-cleaning-tank-at-bijnor-sugar-mill/
4) 4 Workers Suffocate in Underground Water Tank — Mumbai (Mar 2025)
Four workers died from suffocation while cleaning a confined underground water tank at a construction site in the Nagpada area of Mumbai.
🔗 Source: NDTV — https://ndtv.in/india/mumbai-4-workers-who-went-to-clean-the-tank-in-under-construction-building-died-of-suffocation-7884044