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Confined space entry, ensuring success
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Probably the most important part, although they all have their particular importance, is the absolute safety inside the confined space. Sure, the worker will know how to accomplish the job and the support crews are well trained, but we need to give those workers the utmost confidence when they make the entry. Start by testing the entire space and surround areas that may have an impact on their safety.
So we test the atmospheric conditions in all areas and all levels of the space before the entry. Why at different levels? Gases, depending on their vapor density, will either sink or rise in an area without any air movement. Gases may stratify; accumulate at different levels, so we test at various levels, maybe every 2’ or so.
Tests are done for:
• oxygen content – between 19.5% and 23.5%
• concentrations of flammable gases; these must be lower than 10% of the lower flammability/explosive limit (LFL/LEL)
• combustible dusts cannot meet or exceed its LFL/LEL
• toxicity – any toxic material that has been or could be present are listed and tested to be below the permissible exposure limit (PEL)
If the air is unsafe according to the tests, the hazard needs to be controlled before anyone enters. Also, if there are any changes in atmospheric conditions, evacuate the space. Retesting (spot checks) is done periodically as long as the space is occupied. The qualified or competent person conducting these test signs the permit and initials each spot check. If hazards cannot be controlled then some sort of supplied air system should be used.
Another concern to be aware of is heat stress. Evaluate for that potential with a Wet Bulb Globe Thermometer (WBGT). An instrument used to determine a composite temperature (humidity, temperature, wind speed, solar radiation) and the effects on the worker.
Even though all of the efforts are placed into a successful entry, you always need to be prepared for an emergency. All emergency equipment is inspected and tested in case it is needed. The safest way to leave the space is a self-rescue, the entrant evacuates with no assistance. There is the non-entry rescue using a lifting mechanism and a harness to allow egress. If you need an emergency response team, those arrangements are made in advance and are available to respond.
Knowing what type of confined space you have, able to recognize any kind of hazard, everyone understanding their role for the entry, documenting the testing results and preparing for emergencies will ensure a safe confined space entry.
There is a certain feeling that workers have after a successful job task, that job well done feeling.
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