As the team approached the gym and art room, CO readings increased to 250 ppm and then spiked to 443 ppm in the art room, below which the boiler room is located. This spike in CO levels prompted Terracon to advise the principal and ESD to call the local Fire Department (FD) and to immediately evacuate the school as soon as possible. Approximately 350 students and school staff calmly exited the building within a few minutes.The FD accessed the boiler room wearing self-contained breathing apparatus and turned off the boiler. FD personnel reported CO concentrations of 450 ppm, and opened doors and windows to ventilate the area. It took two hours for CO to drop below dangerous levels. Following the FD “all clear,” the district’s building engineers entered the room to service the boiler. What they found was surprising – in a bend of the 12” diameter boiler exhaust flue was a large dead owl. It appeared the bird had somehow entered the exhaust flue, was overcome by CO, and died. The remains partially blocked the exhaust flue, causing CO and other gases to back-flush and accumulate in the boiler room, eventually infiltrating into the school. The next morning the Terracon team returned to the school prior to monitor CO levels. Within 30 minutes of the boiler restart, the team detected 180 ppm of CO in the boiler room, but nowhere else in the building. After the engineers made additional repairs, the boiler operated for several hours as Terracon monitored CO levels throughout the school – none was detected. Just to verify that there were no more CO issues at the school, Terracon returned the following day and found the boiler and exhaust flue performing correctly with no CO detected. To help concerned parents understand the situation more clearly, Terracon scientists participated in several meetings held at the school to explain what happened, and the steps taken to protect the students’ and teachers’ safety. The carbon monoxide infiltration appeared to be a confluence of circumstances. The boiler had likely been malfunctioning prior to the owl being trapped in the exhaust flue, but its presence intensified the problem and facilitated infiltration of carbon monoxide into the school. The result was exposure to dangerous concentrations of CO. The school district requested that Terracon spot-check CO levels at 82 schools with similar boiler types. By cross-training personnel from other Terracon practice groups in the Dallas office, the team completed the survey in four days. Of the 82 schools surveyed, two were found to have malfunctioning boilers. These boilers were repaired, and the district was confident that there were no other CO safety issues. At Terracon’s recommendation, the district is allocating funds to install carbon monoxide alarms in each school’s boiler room as an additional safety precaution. Presented with this serious CO exposure event, Terracon stepped forward as the school district’s trusted advisor and showed the commitment to being responsive, resourceful and reliable – no matter what hour of the day.