Determining the Hazards in Confined Spaces

Blog Post created by nancypearce Employee on Aug 30, 2012

Because confined spaces are not designed for human occupancy they have hazards that are not typically found in locations that ARE designed for occupancy.  So what about the person who has to enter those spaces to perform work?   Confined spaces are usually not well ventilated and may have unguarded equipment that would not be expected to be found in occupied areas.   They may have inwardly converging walls or convoluted piping that could lead to entrapment.  Once you have identified your confined spaces, the first step prior to entry is to determine the potential hazards that may exist in those spaces.  Hazard Identification is one of the most critical components of a confined space safety program.  If a hazard is not identified, then it cannot be eliminated or controlled!  That omission could lead to a fatality.     

Confined space hazards can generally be placed in two categories-atmospheric and physical hazards. Atmospheric hazards fall into four general categories-toxic, oxygen deficient, oxygen enriched and flammable environments.  Atmospheric hazards are invisible. The air in confined spaces looks and often smells just like the outside air, so workers entering the space may not recognize that the atmosphere is dangerous. A well chosen, calibrated gas monitor used to properly monitor the air is the way to insure the atmosphere is safe and that there is sufficient oxygen for breathing. The atmosphere in a confined space may also lead to explosions or fires.  Gas monitors check for flammable atmospheres and for oxygen enriched atmospheres that can increase the risk for and intensity of a fire. 

 In addition to gas monitoring, it is critical that a visual inspection is conducted to look for potential residues and other hazards in the confined space that may not be detected on the gas monitor.  It is important to review the list of chemicals that may have been stored or used in the space previously.  Furthermore, there must be a determination of potential atmospheric hazards that will be brought INTO the space or may be created by the work being done in the space.  Atmospheric testing may show a safe environment prior to entry, but fumes and combustion by-products will be of concern if welding is to be performed in the space. Cleanup of debris in the bottom of the tank could stir up toxins and hazards that may not show up on the gas monitor when the debris is untouched prior to entry. The evaluation of hazards must include what exists before entry as well as what hazards may occur while the worker is inside the space.   

Safety hazards in confined spaces include entrapment and engulfment as well as physical hazards caused by mechanical or electrical equipment.  The configuration of a tank with inwardly converging walls could lead to entrapment of a worker.  Solid materials such as grains or sand can lead to engulfment.  Liquids inside a space could lead to drowning.  It is critical that the hazard assessment determine if there are process related lines that enter the space.  These will need to be isolated from the space prior to entry.   A determination must be made to see if there are rotating parts, exposed electrical, hydraulics or other energy sources that will need to be eliminated or controlled prior to entry.   A Lockout/Tagout program typically goes hand in hand with a confined space entry program. See OSHA 1910.147 

There are numerous other health and safety hazards that are also common for confined spaces including noise and heat, cold extremes, slips and falls that should also be included in assessment.

One could argue that hazard assessment is the NUMBER ONE priority for preventing confined space entry fatalities.  A hazard that is not identified cannot be eliminated or controlled. 


NFPA is developing a best practices document for confined space entry.  Hazard assessment will be an important part of this document. How do you insure that all hazards are identified in your confined spaces?  Do you use a checklist/permit?   How competent is the person who is evaluating your confined spaces?   Do you include a list of hazards that will be brought into the space as a result of work being performed?What about adjacent spaces (see previous blog)?

If you have suggestions for what should be included in the hazard assessment or in the new document in general, please let us know!