Identification of Confined Spaces
The Production should identify all confined space areas present on production facilities and locations. When possible, confined space locations shall be marked or labeled with the following or similar language to prevent unauthorized entry:
UNAUTHORIZED ENTRY PROHIBITED
The Confined Space Survey Form shall be used to document the confined space identification survey. Copies of all confined space surveys should be forwarded to the Production Safety Consultant. The following confined space classifications should be used:
- Permit Required
- Non-Permit Required
- Hazardous Atmosphere Only Space (Reclassified non-permit space)
Once a space has been classified as confined, all hazards which may be present within that confined space must be identified. The four types of hazards typically present in confined spaces are as follows: Oxygen-Deficient Atmosphere, Flammable Atmosphere, Toxic Atmosphere and Mechanical / Physical Hazards. These four hazards are discussed in detail below.
The normal atmosphere is composed of approximately 21% oxygen and 79% nitrogen. An atmosphere containing less than 19.5% oxygen is considered to be oxygen-deficient. The oxygen level inside a confined space may be decreased as the result of either consumption or displacement of oxygen. There are a number of processes, which consume oxygen in a confined space. Oxygen is consumed during combustion of flammable materials, as in welding, cutting, or brazing. In addition, oxygen can be consumed during chemical reactions such as in the formation of rust on the exposed surfaces of a confined space. Oxygen levels can also be reduced as the result of oxygen displacement by other gases.
Flammable atmospheres are generally the result of the presence of flammable gases, vapors or dust mixed in certain concentrations with air, or an oxygen-enriched atmosphere. An oxygen-enriched atmosphere will cause flammable materials such as clothing and hair to burn violently when ignited. Combustible gases or vapors can accumulate within a confined space when there is inadequate ventilation. Gases that are heavier than air will accumulate in the lower levels of a confined space. It is therefore very important that atmospheric tests be conducted near the bottom of all confined spaces. At times the work being conducted in a confined space can generate a flammable atmosphere. Work such as spray-painting, coating, or the use of flammable solvents for cleaning can result in the formation of an explosive atmosphere. Welding or cutting with oxygen / acetylene equipment can also be the cause of an explosion in a confined space and shall not be allowed without an authorized hot work permit. Oxygen and acetylene hoses may have small leaks, which could generate an explosive atmosphere and, therefore, should be removed from the space when not in use. The atmosphere shall be tested continuously while any hot work is being conducted within a confined space.
Toxic Atmospheres may also be present within a confined space. Products which are stored in a confined space can be absorbed by the walls and give off toxic vapors when removed or when the residual material is cleaned. These products can also produce toxic vapors which typically will remain in the atmosphere of the confined space due to poor ventilation. Toxic atmospheres can also 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 can also produce highly toxic vapors. It is also possible for toxic atmospheres that are produced by processes near the confined space to enter and accumulate in a confined for example, if the confined space is lower than the adjacent area and the toxic gas or vapor is heavier than air, the toxic gas or vapor may "settle" into the confined space.
Mechanical / Physical Hazards
Problems such as rotating or moving mechanical parts or energy sources can create hazards within a confined space. All rotating or moving equipment such as pumps, process lines, electrical sources, etc., within a confined space must be identified. These types of hazards must be locked or tagged-out. Physical factors such as heat, cold, noise, vibration, and fatigue can contribute to accidents. These factors must be evaluated for all confined spaces. Excavations can present the possibility of an engulfment hazard. Employees shall be protected from cave-ins by sloping, benching, or shoring systems as appropriate depending on the depth and configuration of the excavation.