Learning from confined space incidents

Confined space incidents tend to repeat themselves. The same hazards, the same assumptions and the same fatal rescue attempts appear in investigation reports decade after decade, in every country and industry. Studying them is one of the best ways to understand why the controls in this course matter. This lesson looks at three well-documented public incidents, one in Canada and two in the United States, and two composite cases built from common patterns, then draws out the lessons they share and shows a simple way to analyse an incident.

The public cases below are summarized from investigation reports and news coverage for awareness, without assigning blame beyond what the investigators found. The composite cases are clearly labelled: they are not descriptions of real events but are typical of many real reports.

Case 1: a mushroom farm pump shed, British Columbia, 2008

On September 5, 2008, at a mushroom composting facility in Langley, British Columbia, two workers and a supervisor were trying to clear a blocked pipe inside a small pump shed connected to the farm's wastewater system. When they separated the pipe, it released toxic gas, most likely hydrogen sulfide and carbon dioxide produced by decomposing organic material. The worker closest to the pipe collapsed. Two coworkers who heard the commotion ran into the shed to help, and they too were overcome. Three workers died, and two others suffered severe, permanent brain damage.

WorkSafeBC's investigation found that the deaths and injuries were preventable. The facility's design, construction and operation allowed gases to build up and pipes to block. The employer had no program for managing the hazards of enclosed spaces and no meaningful safety procedures; the only precaution was an informal reminder to be careful. Workers had no gas detection, ventilation, isolation, attendant or rescue plan. The regulator had also received earlier complaints about air quality at the farm. The company and its owners were later fined under workplace safety law, and a coroner's inquest made recommendations about training, inspections and the protection of farm workers.

Key lessons: a small shed or pump house can be a confined space; disturbing pipes or sludge can release a sudden burst of gas; and untrained coworkers who rush in become victims.

Case 2: nitrogen at a refinery reactor, Delaware, 2005

On the night of November 5, 2005, contract workers at a refinery in Delaware City, Delaware, were reinstalling a large pipe elbow on top of a hydrocracker reactor during a maintenance shutdown. The reactor was being purged with nitrogen, so its atmosphere contained almost no oxygen. A roll of duct tape fell through the 24-inch (61 cm) opening onto a tray about five feet (1.5 m) inside the reactor. Entering to retrieve it would have required a specially equipped crew under the site's permit rules, which would have delayed the job. According to the U.S. Chemical Safety Board (CSB), one worker tried to hook the tape from the opening, most likely sitting on the ledge; the CSB could not determine whether he entered deliberately or slipped in, but he ended up on the tray. A second worker climbed in with a ladder to help him. Both were asphyxiated. An oxygen measurement in the reactor afterwards showed less than 1 per cent oxygen.

The CSB found that workers were not adequately warned that oxygen-deficient atmospheres could exist at and around the openings of purged equipment, that the opening was marked with a sign and tape but not barricaded, and that training on nitrogen hazards and on not attempting emotional rescues was inadequate. It recommended better training on inert gas purging and on the hazards around openings.

Key lessons: inert gases give no warning; the area at and just inside an opening can be deadly; a dropped tool or object is never a reason to break the plane of an opening without a permit; and the instinct to rescue kills.

Case 3: fire in a hydroelectric penstock, Colorado, 2007

On October 2, 2007, workers were recoating the inside of a long, steel-lined tunnel called a penstock at a hydroelectric plant near Georgetown, Colorado. The penstock runs thousands of feet, deep underground, and the workers were using epoxy coatings and highly flammable solvents inside it. A fire started inside the tunnel. Five workers who were farther up the sloping tunnel, beyond the fire, could not escape: the CSB described how the only way out was past the fire, and they died. Three others were injured.

The CSB found that the utility and its contractor had not adequately prepared for the hazardous work in the confined space. Flammable vapours were not adequately controlled or monitored, and there were no technically qualified rescuers on standby. The CSB issued 20 recommendations, including continuous monitoring of flammable atmospheres, treating large spaces such as penstocks as permit spaces, planning alternative escape routes or refuge chambers where there is only one exit, providing standby rescue teams where hazards threaten life, and improving contractor oversight.

Key lessons: a confined space can be very large; the work can create the hazard; a single exit means a fire, flood or collapse can trap everyone beyond it; and rescue teams must be at the space when the hazards are life-threatening.

Composite case A: a grain bin

This composite case is typical of many agricultural reports. A farm worker notices that grain has stopped flowing from a bin. Thinking it has bridged, he climbs in through the roof hatch with a shovel while the unloading auger is still running, intending to break up the crust. The crust gives way and he is pulled into the flowing grain. Within seconds he is buried to his chest and cannot move. A family member hears him shout and climbs in to help, but she sinks too. The auger is eventually shut off from outside, and fire and rescue services use a rescue tube to free the second person, but the first worker has suffocated.

What would have prevented it: locking out the unloading equipment before entry; breaking the bridge from outside; a harness and lifeline tied off and tended by an attendant; a rescue plan; and, above all, not entering.

Composite case B: a sewer connection

This composite case is typical of municipal reports. A contractor crew is connecting a new line to an existing sewer manhole. The manhole is deeper than a person is tall. A worker climbs down to check the connection without testing the air, because the job will only take a few minutes and the crew has done many similar connections. At the bottom, disturbed sediment releases hydrogen sulfide and the worker collapses. A second worker goes down the ladder and also collapses. A third worker, remembering his training, stays at the top, calls emergency services and keeps others away. Firefighters with breathing apparatus recover both men; one survives with injuries.

What would have prevented it: testing from outside at all levels, ventilation, continuous monitoring, a harness and retrieval system on a tripod, an attendant, and a rescue plan.

The common threads

Across these cases and many others, investigators keep finding the same contributing factors:

• the space was not recognized as a confined space, or its hazards were underestimated, especially small sheds, pits and the areas at openings;
• the atmosphere was not tested, or was tested only once, or not at the right level;
• the work, such as disturbing sludge, separating a pipe, coating or using solvents, created or released the hazard;
• energy and material inflows were not isolated;
• there was no attendant, or the attendant had other duties or went in;
• there was no rescue plan, no retrieval equipment set up and no rescuers available in time;
• untrained coworkers entered to help and became victims;
• production pressure, a quick job or a familiar task led people to skip steps;
• contractors and host employers did not share information about the hazards.

These threads map directly onto the controls in lessons 3 to 10. No incident in this lesson required an unknown hazard or bad luck. Each happened when known controls were missing.

Analysing an incident: barrier analysis

A simple way to learn from an incident, or to review a planned entry, is barrier analysis. List the barriers that should stand between the hazard and the worker, then ask, for each one, whether it was present, whether it worked and why not. In confined space work the main barriers are: recognizing the space; avoiding entry; isolation; cleaning and ventilation; testing and monitoring; the permit; the attendant and communication; retrieval equipment; and planned rescue.

Barrier analysis is useful not only after incidents but before entries. Teams can use it to check a draft permit: if any barrier is missing, the entry is not ready.

Near misses and reporting

For every confined space fatality there are many near misses: a detector alarm that sent workers out in time, a missed valve discovered during verification, a rescue drill that showed the tripod would not fit. Reporting and investigating these events, without blame, lets the program improve before someone is hurt. A culture in which people report problems with permits, equipment and procedures, and in which those reports lead to visible changes, is one of the strongest protections a workplace can have.