Confined Space Characteristics

Confined Space Characteristics are discussed and analyzed.

In a previous post we discussed a basic overview of confined spaces and the perils they play in industry, especially construction and manufacturing. We examined the tendency for employers to underestimate the danger of these enclosed spaces, and the fact that asphyxiation and mechanical trauma are the two major causes of deaths. In this post we will take a look at confined space characteristics as a foundation to recognition and identification.

First, it is important to identify exactly what regulatory agencies define as confined space characteristics. In general, NIOSH, the National Institute for Occupational Safety and Health (part of the Center for Disease Control), defines a confined space as any space that has at least one of the following characteristics:

1. Limited openings for entry and/or exit

2. Unfavorable natural ventilation

3. Not designed for continuous worker occupancy

This definition compares favorably to that as defined by OSHA in 29 CFR 1910.146

Confined Space Characteristics: Limited Openings for Entry and/or Exit

When we speak of confined space characteristics, the first pertains to the fact that these are spaces whose openings are limited by size or location. In many case, openings are quite small in size, perhaps only 18 inches in diameter, and are difficult to move through easily. Because of these small openings, workers usually find it tedious to traverse these spaces on their own, but even more so with additional equipment such as personal protective equipment, respirators, or rescue equipment.

Not all confined spaces are necessarily characterized with small openings, however. In many cases these spaces may be quite large, such as pits, degreasers and excavation sites that may seem to not fit the traditional vision of a confined space. Nevertheless, these spaces many times are accompanied by ladders, hoists or other devices that can impede escape in emergency situations.

 Confined Space Characteristics: Unfavorable Natural Ventilation

Most confined spaces are designed in such a way as to impede the natural flow of air into and out of the space. As a result, these restricted areas can cause an abnormal atmosphere that is markedly different than the atmosphere outside. It is not unusual for deadly gases to accumulate, especially in the case where these spaces are adjacent to chemicals or even decomposing organic substances. The mix inside the space may reduce the oxygen tension to levels that are inhabitable, or in some cases, may cause a situation where there is too much oxygen and it mixes with particulates to form a hazardous situation for fire or explosion should a source of ignition be present.

Confined Space Characteristics: Not Designed for Continuous Worker Occupancy

Most all confined spaces, while ubiquitous, are typically not designed for workers to enter and work on a routine basis. These spaces are designed for their own specific purposes such as to store a product, enclose materials, surround intricate machinery, provide as inflow or outflow of fluids or otherwise transport substances. Their restricted nature is intentional and only requires a worker to enter during times of inspection, maintenance, repair or cleanup. Many times this access is difficult and dangerous due to chemical or physical hazards within the confined space.

It isn’t unusual for a confined space to have combinations of these three characteristics. As such, the increased level of risk needs to be readily recognized so that workers are keenly aware of the hazardous nature of their existence. It is important to remember also, that confined spaces can pose significant dangers to those that may be involved in rescue operations also. This should be identified during normal, scheduled plant or site surveys.

We have presented the characteristics of typical confined spaces in this post so that we might lay a foundation for actions that can be taken to mitigate the hazardous conditions that exist. In our next post we will explore in greater detail what workers and employers can do to be aware of the hazards involved in entering and working in these areas.