A malfunctioning boiler caused a buildup of carbon monoxide that sent six people from a North Vancouver apartment building to hospital over the summer, according to a report from Technical Safety B.C. Released last month, the report details the circumstances that led to the frightening incident at the 25-unit building on Aug. 10 of this year. The document does not specify where in North Vancouver the building is located, but describes it as three storeys tall and built in 1967. According to the report, the building is heated by a pair of natural-gas-burning boilers in a mechanical room in the basement. These boilers were set to automatically turn off when outdoor temperatures were above 65 degrees Fahrenheit (18.9 C). While one of the two was accurately sensing the outdoor temperatures and shut down, the other was not, the report notes. Instead, it was cycling on and off as needed to keep the water inside it warm. “At the time of the incident, the outdoor temperature was above the summer shutdown setpoint, so Boiler 1 and the pump were off while Boiler 2 continued to operate without system circulation,” the report reads. “Boiler 2 fired only until the stagnant water inside the boiler reached the operating temperature, then shut off again. This caused short cycling and increased the number of ignition attempts.” When the outdoor temperature dropped below the set point overnight, the first boiler would turn on and the system’s pump would send cold water into Boiler 2, leading it to run for a longer time period. “On the night before the incident, delayed ignition during one of the boiler’s frequent ignition attempts likely produced enough force to dislodge the vent from the appliance vent connection,” the report continues. “The vent wedged against the new external low-water cutoff and remained there, leaving the boiler vent outlet open to the mechanical room. No safety system identified that the vent connector had disconnected from the boiler. When the boiler ignited on subsequent attempts, it continued to operate while expelling flue gases into the mechanical room.” Later that night, when the outdoor temperature dropped, the second boiler again ran for an extended period of time. “During this run time, the disconnected vent allowed flue gases to spill into the mechanical room. Combustion by the boiler and recirculation of flue gases reduced the oxygen available for combustion. The reduced oxygen supply caused incomplete combustion, which significantly increased CO production.” This carbon monoxide made its way into the upper floors of the building through holes and gaps in the basement ceiling, according to the report. There were no carbon monoxide alarms in the building, the report notes, so no one realized what was happening until morning, when several people began displaying symptoms of carbon monoxide poisoning. “One occupant, whose family members experienced severe symptoms beginning around 6 a.m., researched the symptoms online and identified CO exposure as a possible cause,” the report reads. “The occupant called 911 around 11 a.m. and informed the building manager’s family, who were in the neighbouring suite.” Paramedics were dispatched and six people were taken to hospital. The report indicates their symptoms included “light-headedness, lethargy, loss of consciousness, headaches, nausea and vomiting.” It also classifies the incident as “major.” The building was evacuated and emergency responders shut down the boilers with help from a technician from “the responding gas utility,” according to the report. “At the time of evacuation, CO levels measured in some areas exceeded the instrument’s maximum display reading of 1,500 (parts per million).”
