Hazards Related to Confined Space

 Confined Space Definitions

• Limited opening for entry and exit.
• Unfavorable natural ventilation.
• Not designed for continuous worker occupancy.
• Excavation deeper than 1.5 meter.

 
Examples of confined spaces


Hazards Associated with Confined Space 

A - Hazardous Atmospheres
1- Oxygen: too little or too much

     Man can live
     3 weeks without food
     3 days without water
     Only 3 min without oxygen

Oxygen Deficient Atmospheres Less than 19.5% by volume
Given a fixed amount of oxygen as you would have in a confined space, respiration of oxygen causes carbon dioxide to increase. When oxygen decreases to less than 19.5%. the atmosphere is said to be oxygen deficient, putting occupants of the confined space at risk of losing consciousness and death.

Here are some common causes of oxygen deficiency in a confined space:
1- Oxygen is used up when metals rust.
2- Oxygen is used up during combustion
— for example, by propane space heaters, during cutting or welding, and by internal combustion engines.
3- Oxygen can be replaced by other gases
— for example, welding gases or gases forced into the space to prevent corrosion.
4- Micro-organisms use up oxygen
— for example, in sewer lines and fermentation vessels. 

 Oxygen Enriched Atmospheres Greater than 23.5% by volume

• Poorly designed or malfunctioning O2 storage or dispensing equipment
• Leaks from oxy-acetylene welding or cutting equipment Couplings, fittings hoses
• Ventilating with pure oxygen.
- Never use pure oxygen to ventilate.
- Never store or place compressed tanks in a confined space.  

 

2- Toxic atmospheres
Toxic atmospheres may be present within a confined space as the result of one or more of the following:
- The Product Stored in the Confined Space: 
 When a product is stored in a confined space, the product can be absorbed by the walls and give off toxic vapors when removed or when cleaning the residual material. The product can also produce toxic vapors that will remain in the atmosphere due to poor ventilation. 

- The Work Being Conducted in the Confined Space: 

Toxic atmospheres can be generated as the result of work being conducted inside the confined space. Examples of such work include: Welding or brazing with metals capable of producing toxic vapors, painting, scraping, sanding, etc. Many of the solvents used for cleaning and/or degreasing produce highly toxic vapors.

- Areas Adjacent to the Confined Space 

Toxic fumes produced by processes near the confined space may enter and accumulate in the confined space. For example, if the confined space is lower than the adjacent area and the toxic fume is heavier than air, the toxic fume may "settle" into the confined space.

   3-Explosive atmospheres Three elements are necessary for a fire or explosion to occur:
1.Oxygen
2.Flammable material (fuel)
3. Ignition source.

B - Physical Atmospheres
1.Slip, trip and fall hazards
2.Falling objects
3.Moving parts of equipment and machinery
4.Electrical shock
5.Loose and unstable materials
6.Substances entering through piping
7.Poor visibility
8.Temperature extremes
9.Noise
10.Risk of drowning
 
Control and Preventive Measures The following measures should be taken where appropriate to prevent deaths and injuries from
confined space work.
1. Risk Assessment 

Prior to commencement of work, a risk assessment must be carried out to identify the hazards associated with the work, assess the risk of accident that may occur, implement SWP and take appropriate measures to eliminate the hazards, or to reduce the risk.

2. Isolation 

- Isolation is the process where a confined space is removed from service and completely protected against any release of energy and/or material.
- Isolation is achieved by bringing any energy source to "zero".
- Equipment may also have several sources of energy.
Isolation can be achieve by:

• Lock and Tag Out all sources of energy.

• De-energizing electrical sources, preferably at disconnect switches remote from the equipment.

• Blanking and Bleeding creating an absolute closure of a pipe, line or duct by fastening a solid plate that completely covers the opening.

• Securing mechanical moving parts within the confined space with latches, chains, chocks, blocks, or other devices. 

3. Gas Check 

A competent person must test and certify the atmosphere of confined spaces for oxygen, flammable and toxic gases or vapours prior to entry. Confined spaces can only be certified safe for entry if:

4. Calibration of Gas Meters 

Gas monitoring devices must be regularly maintained and their accuracy verified with functional (bump) tests and full calibrations. A functional test is a brief exposure of the gas monitor to a known gas for the purpose of verifying sensor and alarm operation. If the instrument fails to operate properly following any functional test, a full instrument calibration should be performed.
A full calibration involves the use of (certified standard) calibration gases, and requires verification that the gas concentrations listed on the cylinder label match the concentration setting for calibration in the instrument. Calibrations must be carried out by trained personnel, and records kept.

5. Entry Permit 

Before entering a confined space, a permit must be issued by a competent person certifying that all hazards have been assessed and precautionary measures have been taken to ensure the safety of entrants.

6. Ventilation

When a confined space is occupied, suitable and adequate ventilation should be provided at all times to provide fresh air and/or to dilute and remove any contaminants to a safe level. It is recommended that a combination of forced or supplied and exhaust ventilation be used to ensure adequate ventilation of the space.
Forced or supplied ventilation introduces fresh air into the space typically through the use of a fan or blower while exhaust ventilation removes contaminants from the space by drawing air out using an extractor.

7. Standby Person 
A watchman should be stationed outside the confined space to keep a look out and render help in the event of an emergency.

 8. Safety Appliances

When entering a confined space, a safety harness and lifeline should always be worn. This will facilitate retrieval during an emergency. Suitable respirators should be worn where toxic gases or vapours are known to be present. Air supplied respirators must be used if the space is likely to be deficient in oxygen or contain unknown or high concentrations of air contaminants.

9. Rescue Plan and Equipment 

A written rescue operation plan should be established and on-site equipment such as retrieval devices and breathing and reviving apparatus should be readily available for emergency use.

10. Training 

 Training should be provided to all persons involved in confined space work, including worker (entrant), standby person, supervisor and gas tester. The training should cover the following areas: 

- General hazards associated with confined space.
- Safety and health precautions with respect to entry into confined space.
- Entry permit system and safe work procedures.
- Emergency response.

11.Personal Protective Equipment The appropriate PPE shall be worn based on the hazard(s) and include:

1. Eye and face protection
2. Head protection
3. Foot and leg protection
4. Body protection
5. Hearing protection
6. Respiratory protection
7. Hand and arm protection
8. Harness, safety belts, and lifelines

 12. Other Safety Measures

Diesel-driven and petrol-driven engines such as pumps and compressors should never be placed inside a confined space.
Host employers should ensure that contractors are competent for work involving a confined space. They also need to brief their contractors on any precautions or procedures to be implemented.
Procedures for emergency response must be established and communicated to all personnel on-site.