In the Spring of 2006, two mechanics at a large factory were performing routine maintenance on a 5,000 gallon mixing tank used in the early stages of production. John was on a ladder inside the tank, and Frank was assisting him from outside the tank. Earlier that day, the tank had been washed out with a toxic chemical cleaner, and the fumes from the residue had begun wafting up from the bottom of the tank.
Since the fumes were starting to bother him up on the ladder, John asked Frank to turn on the mixing tank's exhaust fan. Frank, who was not familiar with the tank's controls, pushed the button he thought turned on the fan. What the button actually did was turn on the mixing blades, which were located halfway up the tank. The blades struck John's ladder, knocking him to the bottom of the tank, where he suffered a concussion and lost consciousness.
Frank, struck by the horror of what he'd done, immediately shut off the mixer blades and climbed into the tank to help John. Unfortunately, he misjudged how long he could hold his breath with adrenaline surging through his body. He was forced to take a breath inside the tank, where oxygen content was low and the heavy, toxic fumes were most concentrated. Before he could pull John out of the tank he was overcome by the fumes, and also lost consciousness.
A nearby co-worker saw what happened and then he also climbed into the tank to help Frank and John. Before he got very far, the chemical fumes burned his eyes and lungs and he climbed back out, and called the fire department to send over their confined space rescue team. The team arrived within minutes, and set up a tripod and harness above the tank, fitted a trained rescue worker with a self-contained breathing apparatus, and pulled out the two unconscious workers with a winch.
Both John and Frank died at the hospital. The other co-worker was hospitalized for several weeks from damage caused by inhaling the fumes. His lungs suffered permanent damage and he will never fully recover.
The preceding is a fictionalized account of a real accident which occurred early in 2006. The names were changed and the company's name has been omitted, but such accidents are not uncommon in the industrial workplace. OSHA mandates that employers must have procedures in place for locking out the power to equipment before working on it, testing the air quality in confined spaces before entering them, and having a rescue plan in place. None of this was done before John and Frank began working on the tank. If it was, none of this would have happened, two men would still be alive, and the third would be in perfect health today.
This type of incident is called a chain reaction confined space accident. When an employee is injured on the job, his co-workers will naturally want to try to help him. In cases like this, however, the danger is invisible and non-obvious, and rushing in to save a friend will only result in another fatality. OSHA has records of up to six people dying in a single chain reaction accident like this. In fact, over half of all confined space fatalities are the would-be rescuers.
Confined Space Safety
A confined space is defined by OSHA as any environment not designed for continuous human occupation. Factors such as limited entrance and exit paths, poor ventilation, and close quarters all play a role in defining a confined space. Common examples include mixing tanks, large ovens, and sewage systems. Unfortunately workers do have to enter confined spaces to perform maintenance from time to time, so safety procedures must be implemented at the workplace.
First, all confined spaces must be clearly marked as such. Employees have a right to know what areas of the workplace require special precautions. A permit procedure should be used to keep track of who has been in the confined space, and no one should ever enter the confined space without a permit, even to help someone in trouble. No one should ever enter a confined space without a watch person who stays outside the space. Yearly training is necessary to keep employees up to date on the current practices and policies.
Second, air quality monitors must be available and used at regular intervals to make sure the atmosphere inside the tank is safe. Oxygen, CO2, carbon monoxide, and other gasses must be within acceptable limits before entering the confined space, and if they fall outside those limits the space must be evacuated immediately. Fans can be used to pump fresh air into the space and pump bad air out, but poor placement could result in one fan simply blowing out the good air the other fan is pumping in, for a total net effect of zero.
Third, special equipment needs to be used in a confined space due to limited access to the exit. Very often it is necessary to attach a harness and winch to the employee entering the confined space so a second employee can drag him out in case of trouble, without having to enter the confined space himself. Other equipment, such as protective gloves, a hard hat, or eye protection, should be used as appropriate. Everything needs to be checked before entering the confined space to make sure it is in good working condition. If there is dangerous equipment in the confined space, such as natural gas burners, mixing blades, or valves used to fill a tank with material, these should all be locked out, following the OSHA lock-out procedure, before entering.
Finally, if something does happen despite all these precautions and an employee becomes trapped, only trained rescue personnel with the appropriate equipment should ever enter the confined space to perform a rescue. Usually this is the local fire department, but sometimes a large factory will have its own trained on-site rescue team. The rescue team needs to be kept informed of all the types of confined spaces they may need to some day enter, so they can have procedures and appropriate equipment ready to attempt a rescue. Performing a confined space rescue is extremely dangerous, so even though it can be difficult to wait for the rescue team to arrive while a friend is in trouble, any untrained workers without special equipment run a serious risk of simply becoming another casualty in a chain reaction.
Complications
turboeye also mentions that policies must be in place for complications arising from the issue of who is and who is not allowed to enter a confined space, and under what circumstances. Possible emergencies, such as a fire, inside a confined space mean that the crews who deal with those emergencies need to be trained how to safely perform their duties in a confined space environment.