By Holly Maher

On Saturday evening, February 22, 2014, 1 person died and 27 others were hospitalized due to carbon monoxide poisoning.  The individuals were exposed to high levels of carbon monoxide that had built up in the basement of a restaurant.  The restaurant was evacuated and subsequently closed until the location could be deemed safe and the water heater, located in the basement, was inspected and cleared for safe operation.

So what caused the fatality and 27 hospitalizations?  We start by asking “why” questions and documenting the answers to visually lay out all the causes that contributed to the incident.  The cause and effect relationships lay out from left to right.

In this example, the 1 fatality and 27 hospitalizations occurred because of an exposure to high levels of carbon monoxide gas, which is poisonous.  The exposure to high levels of carbon monoxide gas was caused not only by the high levels of carbon monoxide gas being present, but also because the restaurant employees and emergency responders were unaware of the high levels of carbon monoxide gas.

Let’s first ask why there were high levels of carbon monoxide present.  This was due to carbon monoxide gas being released into the basement of the restaurant. The carbon monoxide gas was released into the basement because there was carbon monoxide in the water heater flue gas and because the flue gas pipe, intended to direct the flue gas to the outside atmosphere, was damaged.  The carbon monoxide was present in the flue gas because of incomplete combustion in the water heater.  At this point in the investigation, we don’t have any further information.  This can be indicated as a follow-up point on the cause map using a question mark.  We have also identified the reason for the flue gas pipe damage as a question mark, as we do not currently have the exact failure mechanism (physical damage, corrosion, etc.) for the flue gas pipe.  What we can identify as one of the causes of the flue gas pipe failure is an ineffective inspection process.  How do we know the inspection process was ineffective?  Because we didn’t catch the failure before it happened, which is the whole point of requiring periodic inspections.  This water heater had passed its annual inspection in March of 2013 and was due again in March 2014.

If we now ask the question, why were the employees unaware of the high levels of carbon monoxide present, we can identify that not only is carbon monoxide colorless and odorless, but also there was no carbon monoxide detector present in the restaurant.  There was no carbon monoxide detector installed because it is not legally required by state or local codes.  The regulations only require carbon monoxide detectors to be installed in residences or businesses where people sleep, i.e. hotels.

Once all the causes of the fatality and hospitalizations have been identified, possible solutions to prevent the incident from happening again can be brainstormed.  Although we still have open questions in this investigation, we can already see some possible ways to mitigate this risk going forward.  One possible solution would be to legally require carbon monoxide detectors in restaurants.  This would have alerted both employees and responders of the hazard present.  Another possible solution would be to require more frequent inspections of this type of combustion equipment.

To view the Outline and Cause Map, please click “Download PDF” above.