Confined spaces are one of the most deadly places in the workplaces. They contains many potential hazards and have restricted exit.
Related to confined spaces, OSHA requires that:
a. All confined spaces in the workplaces shall be identified.
b. Confined work spaces shall be treated as hazardous until proven.
c. Their hazards should be identified.
d. Appropriate respond should be given to these hazards before entry.
Their hazards can be divided into:
- hazardous atmosphere,
- physical hazard,
- chemical contact hazard,
- biological hazard.
Common Confined Space Hazards
1. Oxygen rich (greater than 23.5%). This condition will introduce fire or explosion, especially when flammable vapor exists. So never use pure oxygen for ventilating a confined area. Use normal air supply only.
2. Oxygen deficient (less than 19.5%). Oxygen deficient or lack of oxygen can cause unconsciousness to death. Oxygen concentration can be declined due to nitrogen intrusion, welding, grinding, oxidation, sandblasting or coating.
3. Oxygen and the existence of flammable vapors or gases can create flammable atmosphere. Chemical reaction and concentration of combustible dust may also create flammable atmosphere.
4. Toxic atmosphere. It is introduced when a toxic chemical or gas is stored in a tank or holder, when carbon monoxide or hydrogen sulphide is produced through decomposition or work being done in the closed space.
5. Corrosive atmosphere. Hydrochloric acid and ammonia are examples of chemicals that can build up a corrosive atmosphere.
6. Physical configuration hazards. The use of ladder and scaffolding, wet surface, uneven bottom, bends in tunnels, narrow area or poor lighting can cause physical hazards to the workers inside confined spaces.
7. Mechanical hazards. Mixing vessel, which is equipped with blades, can introduce mechanical hazard when workers come into the confined work space (mixing vessel). Including in this is falling object.
8. Surface hazard, for instance slips and falls.
9. Noise hazards. Grinding work inside a confined work space can result high level noise.
10. Vibration hazards.
11. Engulfment hazards. Engulfment hazard may happen when worker is entrapped by content of the confined space.
12. Temperature. Cold temperature and heat create temperature hazard.
Always bear in mind that hazards identification shall be finished before entering a confined space. Then, provide appropriate controls to these potential hazards afterward.
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Steps to safely enter a Confined Space
Acquire a Permit
Most spaces require a permit by the organization carrying out the work before workers can enter. Ensure your employer or unit has obtained the necessary permit. It should be prominently displayed at the space during an entry.
Control Hazardous Energy
Make pertinent use of locks and tags to prevent accidental startup of equipment. Cut off steam, water, gas or power lines that enter the space. Lock out / tag out is a good system for that. Use only safe, grounded, explosion proof equipment and fans if there is a possibility of a combustible atmosphere developing.
Test the Air
Use the necessary equipment for checking oxygen levels, combustibility and toxicity levels in confined spaces. Test before the space is opened by probing with the test apparatus near the entry.
Once the space is opened, sweep the probe from top to bottom to test the entire space. Heavy combustible gases like propane and butane sink, while light gases like methane will rise to the top. Test the oxygen levels and for toxicity as well. Notify your superior if tests find hazards that you cannot protect against adequately. Continue testing the air quality during work to further guard against buildup of dangerous gases or oxygen deficiency.
Purging and Ventilating
Purge and remove all unwanted water, atmospheres, sediments, or other substances before entry, as these may all become safety hazards.
Finally, use ventilating equipment whenever possible to maintain the oxygen level between 19.5 and 23.5%. Toxic gases and vapors, if present should also be kept to within acceptable levels. If ventilation or purging does not eliminate all atmospheric hazards, appropriate respiratory protection is mandatory before commencing work. Eye and hearing protection may also be necessary.