Environmental, Health and Safety Services

Confined Spaces 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. If a hazard cannot be eliminated or isolated, contact EHS for review and recommendations.

Hazardous Atmosphere

Hazardous atmospheres are the leading cause of deaths in confined spaces. This condition is often 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. 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% 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%, but greater than 1% or 2%, 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 ist 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:
  • 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 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.




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 stangulation, 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.


Feed Binds

Feed Bins

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. The atmosphere at this bottom cross-section may be hazardous, or there may be mechanical hazards (e.g. augers) which 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 exposure 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 inherent fall hazards, use of hazardous chemicals or degreasers, or performing welding and cutting in a confined space. Hazards must be evaluated by the Entry Supervisor and necessary controls implemented to eliminate or isolate the existing or potential hazard(s).

Hazardous Energy Sources

Hazardous energy sources in VT confined spaces typically include high voltage, steam, or mechanical hazards. For more information on hazardous energy and Virginia Tech's Lockout/Tagout Program, click here. The hazardous energy must be isolated or removed from service prior to entering the space. The energy control method used must completely protect employees from the release of energy or materials into the space.


Steam Tunnel

Many campus confined spaces, such as the steam tunnels and large ovens, may have elevated temperatures which can increase the risk of heat stress or heat stoke. Heat stress conditions exist when high temperatures and humidity and limited air movement are present. Other factors include direct sun or heat sources, physical exertion, poor physical condition or medications taken by an individual, or an inadquate tolerance for hot workplaces.