A confined space is typically large enough and constructed that a person can enter and perform assigned work; with limited or restricted means for entry or exit and is not designed for continuous or normal occupancy. In many cases, tanks, vessels, manholes, silos, storage bins, hoppers, vaults, and pits, are all spaces with limited entry space and would be considered a confined space.
Those working in confined spaces can face life-threatening hazards from toxic substances to electrocutions. Due to the hazardous working conditions, OHSA has and continues to publish guidance in keeping workers safe. Standards for Confined Space in Construction or other Compliance Materials published by OHSA are located here.
In order to understand confined space entry, below we’ve highlighted a number of confined spaces and the requirements that define them.
- Permit-Required - A confined space that requires a permit if it has one of the following characteristics below. The safety department of the company is required to have this permit system that ensures the area is safe when entered, and informs all parties of maintenance times including all operators are aware of who is inside and that equipment is shut off.
- Contains or has a potential to contain a hazardous atmosphere.
- Contains a material that has the potential for engulfing the entrant.
- Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes.
- Contains any other recognized serious safety or health hazard/s.
- Non-Permit Required - a confined space that does not contain or, with respect to atmospheric hazards, have the potential to contain any hazard capable of causing death or serious physical harm. If a place is free of a hazard, then an entry permit isn’t required.
- No-Entry Confined Space - A space where workers are not allowed to enter.
- Hazardous Atmospheres - An atmosphere which poses a danger to both the location/equipment and persons entering. Hazardous Atmospheres can be defined as:
- Flammable – known as enriched oxygen atmospheres, vaporization of flammable liquids, chemical reactions, and concentration of combustible dust or absorption of chemicals from inner surfaces of the confined space.
- Toxic - Entire spectrum of gases, vapors, and air-borne dusts. Some examples of toxic atmospheres are manufacturing processes such as charcoal, product storage such as removal of a substance from a tank or maintenance work such as welding in a confined space.
- Irritant/Corrosive - Normally these types of atmospheric hazards are divided into primary and secondary groups.
- Primary irritants exert no systemic toxic effects because the products formed by them on tissues of the respiratory tract are non-irritant and other irritant effects are so violent as to obscure any systemic toxic action. Examples are chlorine, ozone, hydrochloric acid, etc.).
- Secondary irritants may produce systemic toxic effects in addition to surface irritation. In most cases, the worker is not aware of any increase in the exposure to these hazardous toxic substances.
- Asphyxiating – Deficiency in of the proper amount of Oxygen. Reduction of oxygen in a confined space may be the result of either consumption or displacement.
- Ventilation - Ventilation requirements are typically pushing about 20 air charges per hour. In lamens terms, every 3 minutes air recharge of air is required.