Once hazards are identified, it is critical to institute appropriate control measures to eliminate or, if not possible, reduce and control confined space hazards. This module discusses the "Hierarchy of Controls" strategies to control confined space hazards. The moment of entry is critical in confined or enclosed space operations. Injuries from fires, explosions, falls, and unsafe atmospheres may be avoided with careful preparation and adequate testing. Remember, acceptable entry conditions must be attained before entry and those safe conditions must be maintained throughout the duration of an entry. This module also explains some of the procedures and precautions that should be in place to safeguard entrants while they are working in the confined space.
The highest priority in controlling hazards in confined spaces should be given to the attempt to totally eliminate the hazard so that entry will be completely safe. That's not possible in many situations, but the attempt should still be considered. For instance, if there is a hazardous atmosphere in the confined space, forced-air ventilation of the space might be the answer to completely eliminate the hazard.
If elimination is not possible, it may be acceptable to replace toxic substances with less toxic or non-toxic substances to that hazardous atmospheres are not created. One primary control measure effective in preventing toxic hazardous atmospheres from developing in the first place is the use of less toxic products that vaporize less readily. Keep less of the product at the site and keep containers closed inside the confined space at all times.
Engineering controls may be employed to design or redesign a confined space so that it hazardous atmospheres and substances do not develop in the workspace. Examples of engineering controls include: installing automatic ventilation systems, redesigning the entrance so that unlimited access is possible, and redesigning an old confined space with a safer confined space configuration.
Administrative controls are those controls which eliminate or reduce exposure to hazards through changes in the work practice (e.g., rotating workers, reducing the amount of worker exposure, housekeeping). Confined spaces should be cleaned/decontaminated of hazardous materials to the extent feasible before entry. Cleaning/decontamination should be the preferred method of reducing exposure to hazardous materials. Where this is not practicable, PPE should be worn by the entry personnel to provide appropriate protection against the hazards which may be present.
If the hazard cannot be eliminated or reduced to a safe level through engineering and/or work practice controls, PPE should be used. A qualified person should determine PPE needed by all personnel entering the confined space, including rescue teams. PPE which meet the specifications of applicable standards should be selected in accordance with the requirements of the job to be performed.
One primary control measure effective in preventing toxic hazardous atmospheres from developing in the first place is the use of less toxic products that vaporize less readily. Keep less of the product at the site and keep containers closed inside the confined space at all times.
Ventilation is one of the most common control methods used in confined spaces to eliminate hazardous atmospheres.
Ventilation helps to:
When ventilation is used to remove atmospheric contaminants from the confined space, the space should be ventilated until the atmosphere is within the acceptable ranges. Ventilation should be maintained during the occupancy if there is a potential for the atmospheric conditions to move out of the acceptable range.
Once it has been determined that the confined space contains a harmful atmosphere, the next step is to clear it. Ventilation blows out oxygen-deficient or contaminated atmospheres and replaces harmful vapors with clean, fresh air. Make sure to ventilate the space thoroughly so that there are no contaminated pockets left, and then test the atmosphere again.
For permit spaces that are deep or have areas leading away from the entry point, the atmosphere may be layered or may be different in remote areas. For these spaces, testing must be done in the area surrounding the worker, which is considered four (4) feet in the direction of travel and to each side. If a sample probe is used to do the testing, then the worker must move slowly enough so that testing is completed, keeping the equipment "response time" in mind, before he/she moves into the new area.
Welding, cutting, burning, and continuous brazing generate hazardous fumes and dusts that can be more effectively removed by local exhaust ventilation systems at or near the point of generation.
When ventilation is not possible or feasible, alternate protective measures or methods to remove air contaminants and protect occupants should be determined by the qualified person prior to authorizing entry.
Conditions regarding continuous forced air ventilation should be used as follows:
After beginning ventilation:
Once entry and work start:
Respirators protect workers against insufficient oxygen environments, harmful dusts, fogs, smokes, mists, gases, vapors, and sprays. These hazards may cause cancer, lung impairment, diseases, or death.
Respirators protect the user in two basic ways.
Respiratory protection is needed in confined spaces whenever:
Inspecting your confined space entry program, procedures, and practices is an important part of the safety management system evaluation. Use a checklist like this to help identify strengths and weaknesses in the program.