By Kim Smiley

A smoking bathroom fan resulted in the disruption of more than a thousand flights in the Chicago area on May 13, 2014 in a dramatic demonstration of real time cause-and-effect.  This incident illuminates how a relatively small issue can quickly grow into an expensive and time-consuming problem.  In an ideal world, a smoking bathroom fan wouldn’t result in national headlines.

So what happened?  How did a smoking bathroom fan that wasn’t even at the airport delay so many flights?  A Cause Map, a visual method for performing a root cause analysis, is a useful tool for understanding the causes that contributed to an issue.   When building a Cause Map, causes are laid out based on cause-and-effect relationships to clearly show what lead to the problem.

In this example, flights were delayed because there was limited support from air traffic control available and air traffic control support is necessary for safe operation.  Air traffic control support was reduced because the Elgin FAA facility that monitors airports in the Chicago area was evacuated for several hours because the building was filled with smoke.  The building had to be evacuated  for personnel safety and  it took some time to reestablish safe conditions.  Emergency personnel had a difficult time pinpointing the source of the smoke because it spread through the space.  The smoke was throughout the building  because the source of the smoke, a bathroom fan, was part of the HVAC system.

The media reports didn’t provide details about why exactly the bathroom fan was smoking in this particular case, but bathroom fans are a relatively common cause of building fires.  Lint or dust can build up in the fan motor over time, eventually leading to the motor overheating.  The situation can quickly become dangerous, particularly when a motor is left powered after it has seized which is a common failure mode for this equipment.

A few fairly easy things can be done to reduce the risk of bathroom fan fires.  Fan should be cleaned at least annually, but should be cleaned more frequently if they appear dirty or dusty.  A motor that is making unusual sounds or noise should be immediately turned off and inspected by an electrician prior to being returned to service.  Any fan that isn’t making the typical whizz sound should also be powered off and repaired or replaced prior to use because a motor that isn’t rotating has a greater likelihood of overheating.   Older models that aren’t thermally protected are most at risk for a fire and replacing them with a newer model with thermal protection can significantly reduce the risk of fire.

To view a high level Cause Map, click on “Download PDF” above.