Environmental Engineering Reference
In-Depth Information
upper compartment can engulf a person inside that compartment, and
survival is doubtful. Industry safety records document the many inci-
dents where farmers and helpers have died due to engulfment in silos.
In the wastewater treatment plant or collection system, engulfment
is also a very real possibility; for example, a clarifier that is emptied for
maintenance but is not properly locked out could trap the workers inside
if the wastestream, under pressure, were to inadvertently enter the clar-
ifier basin and rise in level at more than 10 feet per minute. Additionally,
collection crews are at risk when working inside an interceptor line
that is not properly locked or tagged out and blinded or blanked with
flanges. The sudden release of the wastestream into the area they are
working in could engulf them. Engulfment can also occur in pumping or
lift station wet wells. Additionally, in excavation work, engulfment can
trap and crush or suffocate workers deep inside a trench that suddenly
collapses.
Physical hazards can also make a confined space entry hazardous.
Physical hazards include machines such as rotating blades or agitators.
Moving parts in confined spaces must be locked or tagged out before
entry is made. Heat stress is another physical hazard often precipitated
by confined space entry. This should not be surprising when one consid-
ers the nature of the atmosphere that is contained in a confined space.
It is not unusual for confined space atmospheres to have temperatures
well above ambient. In addition to the normal heat sink qualities of some
confined spaces, the heat stress problem is greatly exacerbated when
someone enters the confined space wearing all of the proper personal
protective equipment, such as self-contained breathing apparatus.
Noise is another physical hazard that most people ignore or do not
think about when confined space entry is made. Noise actually reverber-
ates in confined spaces and can cause permanent hearing loss. Hearing
protection may be required to protect those entering a confined space.
Another physical hazard in confined spaces is falls. Falls in confined
spaces can be fatal. Falls are common because confined spaces are usu-
ally entered via ladders. Ladders are inherently dangerous, and their
danger is magnified exponentially when used in confined spaces.
When improper confined space entry procedures are used in a
space with an undetected contaminant present, a common thread runs
through all of these incidents—that is, fatalities are almost always the
result. Confined spaces can be very unforgiving. Unfortunately, experi-
ence has shown that confined space mishaps often result in the deaths
of more than one individual due to what the author refers to as the
john
Wayne syndrome
. For example, it is not unusual for someone who finds
a victim unconscious in a wet well to attempt heroic rescue efforts to
free the victim, with total disregard for his or her own safety. Thus, the
John Wayne syndrome has caused the confined space tragedy to become
a multiple-victim incident.
Confined space entry relies on additional safety programs to ensure
safe entry. As pointed out earlier, a confined space should not be entered
unless proper lockout/tagout procedures have been effected to prevent
