Scope and application. This Subpart applies to work in confined and enclosed spaces and other dangerous
atmospheres in shipyard employment, including vessels, vessel sections, and on land-side operations regardless of geographic location.
Definitions applicable to this Subpart:
"Adjacent spaces" means those spaces bordering a subject space in all directions, including all points of contact, corners, diagonals,
decks, tank tops, and bulkheads.
"Assistant Secretary" means the Assistant Secretary of Labor for Occupational Safety and Health, or designated representative.
"Certified Industrial Hygienist (CIH)" means an industrial hygienist who is certified by the American Board of Industrial
"Coast Guard authorized person" means an individual who meets the requirement of Appendix B to subpart B of this part 1915 for tank
vessels, for passenger vessels, and for cargo and miscellaneous vessels.
"Dangerous atmosphere" means an atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to
self-rescue (i.e., escape unaided from a confined or enclosed space), injury, or acute illness.
"Director" means the Director of the National Institute for Occupational Safety and Health, U.S. Department of Health and Human Services,
or designated representative.
"Enter with Restrictions" denotes a space where entry for work is permitted only if engineering controls, personal protective equipment,
clothing, and time limitations are as specified by the Marine Chemist, Certified Industrial Hygienist, or the shipyard competent person.
"Entry" means the action by which a person passes through an opening into a space. Entry includes ensuing work activities in that space
and is considered to have occurred as soon as any part of the entrant's body breaks the plane of an opening into the space.
"Hot" work means any activity involving riveting, welding, burning, the use of powder-actuated tools or similar fire-producing operations.
Grinding, drilling, abrasive blasting, or similar spark-producing operations are also considered hot work except when such operations are isolated
physically from any atmosphere containing more than 10 percent of the lower explosive limit of a flammable or combustible substance.
"Immediately" dangerous to life or health (IDLH) means an atmosphere that poses an immediate threat to life or that is likely to result in
acute or immediate severe health effects.
"Inert" or "inerted atmosphere" means an atmospheric condition where:
 The oxygen content of the atmosphere in the space is maintained at a level equal to or less than 8.0 percent by volume or at a level
at or below 50 percent of the amount required to support combustion, whichever is less; or
 The space is flooded with water and the vapor concentration of flammable or combustible materials in the free space atmosphere above
the water line is less than 10 percent of the lower explosive limit for the flammable or combustible material.
"Labeled" means identified with a sign, placard, or other form of written communication, including pictograms, that provides information
on the status or condition of the work space to which it is attached.
"Lower explosive limit (LEL)" means the minimum concentration of vapor in air below which propagation of a flame does not occur in the
presence of an ignition source.
"Marine Chemist" means an individual who possesses a current Marine Chemist Certificate issued by the National Fire Protection
"Not Safe for Hot Work" denotes a space where hot work may not be performed because the conditions do not meet the criteria for Safe for
"Nationally Recognized Testing Laboratory (NRTL)" means an organization recognized by OSHA, in accordance with Appendix A of 29 CFR
1910.7, which tests for safety and lists or labels or accepts equipment and materials that meet all the criteria found in 1910.7(b)(1) through
"Not Safe for Workers" denotes a space where an employee may not enter because the conditions do not meet the criteria for Safe for
"Oxygen-deficient atmosphere" means an atmosphere having an oxygen concentration of less than 19.5 percent by volume.
"Oxygen-enriched atmosphere" means an atmosphere that contains 22.0 percent or more oxygen by volume.
"Safe for Hot Work" denotes a space that meets all of the following criteria:
 The oxygen content of the atmosphere does not exceed 22.0 percent by volume;
 The concentration of flammable vapors in the atmosphere is less than 10 percent of the lower explosive limit;
 The residues or materials in the space are not capable of producing a higher concentration than permitted in paragraph (1) or (2) of
the above, under existing atmospheric conditions in the presence of hot work and while maintained as directed by the Marine Chemist or competent
 All adjacent spaces have been cleaned, or inerted, or treated sufficiently to prevent the spread of fire.
"Safe for Workers" denotes a space that meets the following criteria:
 The oxygen content of the atmosphere is at least 19.5 percent and below 22 percent by volume;
 The concentration of flammable vapors is below 10 percent of the lower explosive limit (LEL);
 Any toxic materials in the atmosphere associated with cargo, fuel, tank coatings, or inerting media are within permissible
concentrations at the time of the inspection; and
 Any residues or materials associated with the work authorized by the Marine Chemist, Certified Industrial Hygienist, or competent
person will not produce uncontrolled release of toxic materials under existing atmospheric conditions while maintained as directed.
"Space" means an area on a vessel or vessel section or within a shipyard such as, but not limited to: cargo tanks or holds; pump or engine
rooms; storage lockers; tanks containing flammable or combustible liquids, gases, or solids; rooms within buildings; crawl spaces; tunnels; or
accessways. The atmosphere within a space is the entire area within its bounds.
"Upper explosive limit (UEL)" means the maximum concentration of flammable vapor in air above which propagation of flame does not occur on
contact with a source of ignition.
"Vessel section" means a sub-assembly, module, or other component of a vessel being built, repaired, or broken.
"Visual inspection" means the physical survey of the space, its surroundings and contents to identify hazards such as, but not limited to,
restricted accessibility, residues, unguarded machinery, and piping or electrical systems.
[59 FR 37816, July 25, 1994]