General Hazard: Confined Spaces

Fire, asphyxiation, toxic exposures upon entry into confined spaces during ship building and repair.

Hazard Description
  • Fumes from residual materials in tanks can create both health and fire hazards. The hazard may be encountered in spaces that have been fumigated or that have contained bulk liquids, gases or solids that are irritants or are toxic or corrosive. Spaces that have contained combustible liquids or gases in bulk are potential fire hazards. Spaces that are immediately adjacent to locations that have contained hazardous materials may contain hazardous gases as well.
  • Pyrolysis products released during hot work (e.g., welding, arc gouging, and flame cutting) - examples are lead, metal fumes, nitrogen dioxide, etc.
  • Solvents, oils, pigments, anti-fouling and anti-rust additives released during painting operations - create both health and fire hazards.
  • Oxygen-deficient atmospheres - asphyxiation hazards occur when gases displace oxygen, which can result from fermentation of cargos, dry ice refrigeration, and cargos that absorb oxygen (e.g., molasses, rusted scrap iron, and various vegetable drying oils in bulk). Compartments that have been recently painted and that are not ventilated, and compartments that have been sealed for an extended period of time may be oxygen deficient, even though tests do not indicate the presence of flammable or toxic contaminants.
  • Asbestos fibers - cause respiratory damage and chronic disease.
  • Cargos that are allergenic or cause skin or respiratory irritations.
  • For additional information, see OSHA's Confined Spaces Safety and Health Topics Page.
  • During outfitting, workers from different trades work together in confined spaces, thereby exposing each other to contaminants.
  • Before entering drydocks, Coast Guard regulations 46 CFR 35.1-1(c)(1) for tank vessels, 14 CFR 71.60(c)(1) for passenger vessels, and 46 CFR 91.50-1(c)(1) for cargo and miscellaneous vessels require that confined spaces (tanks, compartments, lines) that contained flammable liquids be cleaned of vapor while still at sea, and be certified by a marine chemist in accordance with NFPA standard 306. However, confined spaces should be tested again by an industrial hygienist or marine chemist prior to entry. For procedural details about cleaning tanks and lines, see Savage.1
  • Periodic checking of confined spaces and tanks on vessels that have carried gasoline and volatile crude oils is required, because rust can continue to dissipate vapor after tanks have been cleaned, and the pumping of ballast may introduce vapor from remote areas of tanks and pipe lines.2,3
    In tanks that have contained gasoline, exposure to lead during welding and cutting operations may result from residual gasoline on rusty surfaces.2
  • Asbestos is still used in certain applications, but improved installation methods generally control exposures. However, removal of insulation poses a considerable hazard. Asbestos removal in confined spaces can create extreme concentrations of fibers.
  • Welding in confined spaces can yield high concentrations of toxic airborne contaminants. For example, welding where surfaces are coated with lead- and chromium-based finishes and galvanized zinc coatings can yield substantial exposures to hazardous materials. Ventilation in confined spaces must be supplied mechanically. Where ventilation provides insufficient protection, supplied-air respirators must be used. For example, in some spaces, the welder must crawl into areas where a gas torch can generate fatal levels of nitrogen dioxide in a few minutes. 2
  • "Skin irritation from cargos is...common."2
  • Also see general hazards for "Respiratory irritation and poisoning from exposure to toxic fumes and particles during welding and cutting operations," and "Exposures to toxic fumes and particles during painting."
  • Certification and testing - potentially dangerous spaces must be tested, inspected, and determined as safe for entry by a marine chemist, industrial hygienist, or other qualified person (see 29 CFR 1915.12). A record of tests must be maintained in accordance with 29 CFR 1915.7(c)(2). Section 29 CFR 1915.14 specifies need for certification by a marine chemist prior to hot work. Section 29 CFR 1915.15 specifies procedures for maintaining gas-free conditions in confined spaces. Section 29 CFR 1915.13 specifies procedures and conditions for performing cold work and cleaning without the space being certified as gas-free.
  • Signs - section 29 CFR 1915.16 requires that conspicuous signs be used to indicate the results of certification inspections.
  • Protocols for entry into confined spaces - precautions that must be taken before entering are specified in 29 CFR 1915.12.
  • Asbestos work - the space must be isolated. Respiratory protection, perhaps requiring flow air-line or powered air- purifying respirators, must be used during insulation removal operations. Portable exhaust systems equipped with high-efficiency particulate filters are used to control exposures on large jobs, as well as vacuum cleaners for asbestos.
  • Welding and cutting operations - additional respiratory protection is often needed when operating in confined spaces. Hazardous surface finishes should be removed before welding. Section 29 CFR 1915.14 specifies that certification by a marine chemist is required before workers may engage in hot work.

1 Savage, K. M. "Marine Gas Hazards Control: Cleaning and Gas-Freeing Shipboard Tanks." National Institute for Occupational Safety and Health (NIOSH) Contract Report 099-74-0002 (NTIS PB-82-225-095). Proceedings of the International Shipyard Health Conference, (December 13-15, 1973).

2 Patty's Industrial Hygiene and Toxicology, Vol II., 1978.

3 Burgess, W. A. "Recognition of Health Hazards in Industry: A Review of Materials and Processes." Wiley- Interscience (1981).