Why maintenance work planning for a confined space entry needs stringent focus or attention ?

  

Let us understand first what is a confined space? Spaces or locations just enough to enter, difficult to enter or exit  and/or not designed for  continuous human occupancy are generally,to my understanding, called confined space.  For example,confined spaces in a process /chemical industry include but are not limited to  tanks, reactors,pressure vessels,columns, volume bottle ,ducts, pipelines, sumps, sewers,  inside culverts and vaults. Confined-space incidents/accidents are  significant cause of workplace death  and injury.  Associated hazards in confined space vary widely; the most common are: oxygen deficiency  presence of flammable materials/ constituents toxic gases or vapors Unless all the above hazards are completely eliminated by taking appropriate  mitigation measures work execution permit shall not be issued.