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Confined Space Hazards

All confined spaces at Virginia Tech are assumed to be permit-required unless evaluated prior to entry and determined to be non-permit required spaces. The presence of any of the hazards listed below deems the confined space a permit-required confined space and actions must be taken to eliminate or isolate the hazard before entering in order to declassify it. If a hazard cannot be eliminated or isolated, the space is considered "permit-required" and Environmental Health & Safety should be contacted for review and recommendations.

Hazardous Atmosphere

Hazardous atmospheres are the leading cause of deaths in confined spaces. This condition is difficult to detect without proper air monitoring equipment. The lack of natural ventilation, the presence of stored materials (such as chemicals), or the work process to be performed in a confined space can result in one or more of the following hazardous atmospheres. Asphyxiation can occur when a substance, such as carbon dioxide, interferes with the oxygenation of tissue. Suffocation can occur when the air supply to the body is blocked from entering the body. Unfortunately, the results can be the same - death. If the condition exists or has the potential to exist, it must be eliminated or isolated prior to entry.

  • Flammable gas, vapor, or mist in excess of 10 percent of its lower flammable limit (LFL/LEL). Sources of flammable gases may come from leaking acetylene hoses, methane gas, chemicals or other products used in the space. If the LEL shows a percentage less than 10 percent, but greater than 1 percent or 2 percent, it would be prudent to investigate possible sources prior to entry and take necessary precautions since conditions can change suddenly.
  • Airborne combustible dust at a concentration that meets or exceeds its lower flammable limit (LFL) can result in an explosion. This concentration may be approximated as a condition in which the combustible dust obscures vision at a distance of 5 feet or less.
  • Atmospheric oxygen concentration:
  • The atmospheric concentration of any substance for which a dose or a permissible exposure limit (PEL) is published by OSHA. Note: An atmospheric concentration of any substance that is not capable of causing death, incapacitation, impairment of the ability to self-rescue, injury, or acute illness due to its health effects is not covered by this definition. Common toxic substances found in confined spaces include:
  • Any other atmospheric condition that is immediately dangerous to life or health (IDLH). For air contaminants for which OSHA has not determined a dose or permissible exposure limit (PEL), other sources of information, such a Safety Data Sheets that comply with the Hazard Communication Standard, published information, and internal documents can provide guidance in establishing acceptable atmospheric conditions.
  • The dust form of some combustible materials may be explosive in the presence of, and proper mixture of, air and an ignition source. The type of "dust" that can result in an explosion is that from any material in its bulk form that will burn, such as coal, cotton, grain, sugar, etc. It does not include dust from soil, which will not burn in its bulk form.
    • Although there is no set parameter for excessive dust in a confined space, there is a rule of thumb that can be followed. When the concentration of dust in the confined space is such that vision is obscured at a distance of 5 feet, it is considered to be potentially explosive and should be controlled through ventilation, wet methods, etc.

Engulfment

Engulfment means the surrounding and effective capture of a person by a liquid or finely divided (flowable) solid substance that can be aspirated to cause death by filling or plugging the respiratory system, or that can exert enough force on the body to cause death by strangulation, constriction, crushing, or suffocation. Examples include grains, sand, soil, rock salt, etc. If the condition exists or has the potential to exist, it must be eliminated or isolated prior to entry.

Entrapment

The space could have an internal configuration that could trap or asphyxiate an entrant, e.g. inwardly converging walls or a floor that slopes downward and tapers to a smaller cross-section, which is common with feed bins (as shown). The atmosphere at this bottom cross-section may be hazardous, or there may be mechanical hazards (e.g. augers) that could seriously injury or incapacitate the entrant. If the condition exists or has the potential to exist, it must be eliminated or isolated prior to entry.

Other Recognized Serious Safety or Health Hazards

Other serious hazards that may pose an immediate danger to life or health must also be considered prior to entry. The determination of whether the resulting exposurepr to a hazard in a confined space would impair the person's ability to perform self-rescue is the aspect that must be considered and addressed prior to entry. Examples may include:

Hazards must be evaluated by the entry supervisor and necessary controls implemented to eliminate or isolate the existing or potential hazard(s) in order to reclassify the space from a permit-required confined space to non-permit-required confined space.