Breaking Conventions Can Cause Accidents

Some time ago I read a newspaper article about a tragedy that occurred in a nursing home. Four elderly residents died after drinking diluted dishwasher cleaning fluid rather than the intended blackcurrant cordial drink. This story stuck in my mind not only because it was a tragedy for the residents, their families, and the staff of the nursing home, but also because it is characteristic of so many accidents: a sequence of unintended events pave the road to disaster.

As a routine safety precaution, the staff at the nursing home stored the dishwasher fluid in a locked cupboard with other hazardous chemicals. Immediately after several residents started to vomit, however, a bottle of dishwasher fluid was found in a cupboard under the sink where staff kept the cordials, presumably because this sites the cordials near the cold water tap required to prepare the diluted drinks.

In total, four factors contributed to the accident:

  1. the dishwasher fluid was stored in the wrong cupboard;
  2. the name of the dishwasher fluid, Rinse Aid, was similar enough to be mistaken at a glance for Ribena, the name of the blackcurrant cordial;
  3. the dishwasher fluid was a dark liquid similar to the purple blackcurrant cordial; and
  4. the size of the dishwasher fluid bottle was similar to the large, catering-size bottle of cordial.

Why was the dishwasher fluid placed in the cordial cupboard rather than in the hazardous-chemicals cupboard, as the nursing home’s safety precautions required? A simple answer is human error, a phrase often used to label the cause of an accident. Everyone makes mistakes and sometimes we are at fault. Sometimes it’s a poor design that doesn’t account for human frailties that’s to blame. At other times, however, the ways in which events, systems and environments interact make mistakes more likely. In the nursing-home accident, the different conventions for storing cordials and cleaning products in the nursing home and in family homes interacted with devastating consequences.

In family homes, cleaning products, such as laundry and dishwasher detergent, are often kept under the kitchen sink and cordials are kept in a cupboard. In the nursing home, it was the reverse: cordials were kept under the sink and cleaning products were locked in a cupboard. Under normal circumstances, the nursing home staff would follow their mental script for returning the dishwasher fluid to the hazardous chemicals cupboard. Sometimes, however, when performing repetitive, routine tasks, we often slip into another routine task. One common example is driving to work on a Saturday morning when we meant to head for the supermarket; we deviate from one familiar mental script—drive to the supermarket—to another familiar mental script—drive to work. It’s likely that the nursing-home return-dishwasher-fluid script was interrupted by a work-related incident. When the staff member returned to the dishwasher fluid, he or she incorrectly resumed the family-home script and returned the dishwasher fluid to the cupboard under the sink where cleaning products are often kept in family homes. An accident was then only a matter of time.

Two of my favorite books on accidents and their causes are James R. Chiles’ Inviting Disaster and Charles Perrow’s Normal Accidents. Both books illustrate that accidents brew from a series of events that combine to produce a disaster. In many cases, each event is often inconsequential; many disasters could have been averted if any one link in the chain of events had been prevented. In the nursing home tragedy, for example, if the dishwasher fluid had been replaced in the correct cupboard there wouldn’t have been an accident, nor would people have died if someone had noticed it was the wrong bottle or been alerted by the detergent’s chemical smell.

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