This case involves a family in Wisconsin that was had their roof replaced with CertainTeed shingles during the summer months. There was a cap vent on the roof which was removed by the roofing company, replaced, and painted during the roof repair. Several months later, the family had a new oil furnace installed. The installation company noticed that the furnace stalled on multiple occasions, and investigated the exhaust vent for blockages. Upon investigating the vent opening on the roof, they found that the cap vent, which was replaced by the roofing company, was flush with the roof – causing most of the fumes to remain trapped inside of the house. The family later tested positive for low-grade carbon monoxide poisoning.
Expert Witness Response E-139043
As a certified InterNACHI home inspector, I am required to know and understand the basics of ventilation. Proper ventilation of gas fired appliances are covered under most jurisdictional Mechanical codes. Furthermore, the manufacturers installation instructions should always be followed when altering a ventilation pipe from a gas or oil fired furnace. Moreover, ventilation pipes are required to extend specific distances above the roof surface. Inadequate ventilation can lead to CO and CO2 buildup if a gas fired appliance is not properly ventilated. Normally CO2 levels outdoors are stated to be 200 ppm to 400 ppm but that level has been rising. Indoor air can be affected by many factors but typically range between 600 ppm and 800 ppm, however in an inadequately vented space 1000 ppm is common. As for CO, 9ppm is the maximum recommended indoor CO level.
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