• Is not primarily designed or intended for continuous human occupancy
• Has limited or restricted entrance or exit, or a configuration that can complicate first aid, rescue, evacuation, or other emergency response activities
• Can represent a risk for the for the health and safety of anyone who enters, due to one or more of the following factors:
  • its design, construction, location or atmosphere
  • the materials or substances in it
  • work activities being carried out in it, or the
  • mechanical, process and safety hazards present

• Poor air quality.
• insufficient amount of oxygen for the worker to breathe.
• toxic gases that could make the worker ill or cause the worker to lose consciousness.
• asphyxiants – simple asphyxiants are gases which can displace oxygen in the air (normally about 21 percent).  Low oxygen levels (19.5 percent or less) can cause symptoms such as rapid breathing, rapid heart rate, clumsiness, emotional upset, and fatigue. As less oxygen becomes available, nausea and vomiting, collapse, convulsions, coma and death can occur. Unconsciousness or death could result within minutes following exposure to a simple asphyxiant. Asphyxiants include argon, nitrogen, or carbon monoxide.
• Chemical exposures due to skin contact or ingestion (as well as inhalation of toxic gases).
• Fire hazard – An explosive or flammable atmosphere due to flammable liquids and gases and combustible dusts which, if ignited, would lead to fire or explosion.
• Process-related hazards – such as residual chemicals, or release of contents of a supply line.
• Physical hazards – noise, heat/cold, radiation, vibration, electrical, and inadequate lighting.
• Safety hazards – such as moving parts of equipment, structural hazards, engulfment, entanglement, slips, or falls.
• Vehicular and pedestrian traffic.
• Shifting or collapse of bulk material (engulfment).
• Barrier failure that results in a flood or release of free-flowing solid or liquid.
• Visibility – such as smoke particles in air.
• Biological hazards – viruses, bacteria from fecal matter and sludge, fungi, or moulds.

Many factors need to be evaluated when looking for hazards in a confined space. There is smaller margin for error. An error in identifying or evaluating potential hazards can have more serious consequences. In some cases, the conditions in a confined space are always extremely hazardous. In other cases, conditions are life threatening under an unusual combination of circumstances. This variability and unpredictability are why the process of hazard and risk identification and assessment is extremely important and must be taken very seriously each and every time one is done.

• The entrance/exit of the confined space might not allow the worker to get out easily should there be a flood or collapse of free-flowing solid.
• Self-rescue by the worker is more difficult.
• Rescue of the victim is more difficult. The interior configuration of the confined space often does not allow easy movement of people or equipment within it.
• Natural ventilation alone will often not be sufficient to maintain breathable quality air. The interior configuration of the confined space does not allow easy movement of air within it.
• Conditions can change very quickly.
• The space outside the confined space can impact on the conditions inside the confined space and vice versa.
• Work activities may introduce hazards that were not present initially.
• Lack of communication between the workers in the space, the attendant and the emergency response team