Hi can you point me in the direction of the other case studies please
OSHA regulation (29 CFR 1910.134(i)(8)) and the American National Standards Institute (ANSI) standard Z88.2, "Practices for Respiratory Protection," specify that respirator air-line couplings must be
incompatiblewith outlets for other gas systems to prevent inadvertent servicing of air-line respirators with non-respirable gases or oxygen.
If an inert gas (e.g., helium, argon, nitrogen) is inadvertently supplied to an air-line respirator rather than breathable air, the results can be fatal. Inert gases such as helium, argon, and nitrogen are widely used in industrial settings as fire suppression blankets for flammable work in confined spaces, to operate pneumatic equipment, and to prevent oxidation in industrial processes.
Air-line respirators are typically used in painting, cleaning, some manufacturing operations, and abrasive blasting. An air-line respirator, whether configured with a hood, helmet, coverall, or facepiece, must have a hose with terminal detachable couplings. When a respirator's air line is connected to a source of inert gas rather than to breathable air, the respirator wearer who trusts his/her sense of breathlessness to determine whether he/she is connected to breathing air has little warning before losing consciousness. This is because the buildup of carbon dioxide, not a lack of oxygen, ordinarily causes the sensation of breathlessness that may alert the individual wearing the respirator. Consequently, the victim is fooled because there is no clear indication that anything is amiss. Blackout occurs quickly, without warning.
Victims wearing respirators connected to inert gas lines are in a zero percent oxygen atmosphere, and unconsciousness can occur in about 12 seconds
2 and death in a matter of minutes. The situation continues to be critical because victims are still wearing respirators and continue to breathe inert gas after they collapse.
Case Histories
Some case histories that appeared in the referenced articles are presented below:
Case #1
An employee was using an air hammer to chip residue out of a furnace at an aluminum foundry. He was wearing an air-line respirator. Two compressed gas lines with universal access couplings were attached to a nearby post. The one on the right was labeled "natural gas." The gas line on the left had a paper tag attached with the word "air" handwritten on it; however, this line actually contained pure nitrogen. A splitter diverted one part of the gas stream to the air hammer and the other part of the stream to the air-line respirator. The employee was asphyxiated and killed when exposed to pure nitrogen.
Case #2
A contractor crew was assigned to abrasively blast inside a reactor vessel at a petrochemical refinery. Although verbal company policy called for contractors to supply all breathing air, this crew, with supervisor's knowledge, had on several occasions used plant air to supply breathing air. A crew member mistakenly hooked up his air-line respirator to an unlabeled nitrogen line (only the shut-off valve was labeled) used by the refinery for purging confined spaces. Plant nitrogen and air lines were identical, and both had couplings compatible with the coupler on the respirator.
Case #3
An employee hooked the fresh air line of his supplied-air respirator into a plant's compressed air lines and began abrasive blasting. The plant operators, unaware that their plant air was being used as breathing air, shut down the fresh aircompressor for routine, scheduled maintenance and pumped nitrogen into the system to maintain pressure and control the valves in the refinery. The employee was overcome by the nitrogen in the air lines and died of nitrogen asphyxia.
Case #4
An abrasive blaster at an air separation plant could not obtain breathing air from an installed line. He adapted unapproved hoses with quick-disconnect couplers so he could connect an abrasive-blasting respirator to a gas line supplying the blasting pot. This piping was not color coded nor labeled in accordance with company policy. The employee died because he did not know he was connecting to a nitrogen line instead of to compressed air. Nitrogen was a separation by-product at this plant and was piped to operate pneumatic equipment.
Case #5
A contract employee was abrasive blasting and painting gratings and railings. The air-line from the abrasive blasting respirator was hooked into the plant air supply. The plant air supply was not Grade D breathing air and was to be used only for valve gauges and pneumatic tools. The air compressor was shut down for maintenance, so nitrogen was backfed into the plant air lines. No one from the company informed the contract employee that the lines now contained nitrogen. When the abrasive blaster donned the abrasive-blasting respirator, he inhaled the nitrogen and was asphyxiated.
