Thursday, November 11, 2010

CO Scare

I think that warnings about common hazards can become so commonplace that we don’t pay enough attention to them. We need something to wake us up. This week I received a wake up call when one of my students showed up to class explaining that his entire family had been suffering from carbon monoxide poisoning. He had missed over a week of classes and had come by once to explain that everyone at his house was sick. His family physician suspected something was up after treating everyone in the family for symptoms that mimicked flu. The doctor confirmed that they were indeed all suffering from CO poisoning. A little investigation revealed that the vent for the furnace in the attic had never been connected. There was a vent pipe, but it ran to within a foot of the horizontal furnace and stopped. The furnace was changed when he purchased the house. He showed pictures of the furnace. It was a model that can be difficult to connect vent to because the vent comes through the front access panel. I imagine the installers did not have the right parts, left it for “later” and forgot about it. The HVAC/R contractor did not get a permit, so there was no county inspector to find the problem. The home inspector did not catch it, from the attic access the vent looks like it is connected. The student thought that he had combination smoke and CO alarms. Turns out, they were just smoke alarms. So an obvious safety hazard that is easily corrected went unnoticed until the weather turned cold. The good news is that nobody died, the house now has CO alarms, and the source of the problem was found and corrected. It is scary to think what the end result could have been if the problem had not been recognized or if the weather had stayed cold for a longer period of time.

More people are sickened or killed by carbon monoxide poisoning than any other type of poison. The Center for Disease Control and Prevention (CDC) reports that each year more than 500 people in the United States accidentally die from carbon monoxide.  An estimated 10,000 people in the U.S. are treated for CO poisoning in hospital emergency rooms annually.  It is believed that many more people suffering CO poisoning are misdiagnosed, or never seek medical care. This is because the symptoms of CO poisoning are very similar to influenza symptoms. One big difference is that influenza causes a fever and CO poisoning does not.
Carbon monoxide is an odorless, colorless gas that is highly poisonous. It is formed by the incomplete combustion of carbon based fuels, like natural gas, oil, coal, or wood.  Incomplete combustion can be caused by lack of oxygen, improper mixing of the fuel and oxygen, or too low a combustion temperature. A correctly adjusted gas or fuel oil flame should produce very low levels of CO. Ideally a correctly adjusted gas or oil flame should produce no CO, but realistically, most produce at least trace amounts. Solid fuels almost always produce large amounts of CO; that is why charcoal comes with a warning that it is not to be used inside.
HVAC/R technicians are in a position to help. We can make sure all combustion appliances in the home are burning correctly, insure there is enough combustion air for proper combustion and venting, and finally by making sure the vent system is adequate and working correctly.  For gas and oil furnaces also remember to inspect the heat exchanger for leaks. The heat exchanger separates the combustion products from the air circulating in the home. Although a defective or cracked heat exchanger can contribute to CO poisoning, more obvious problems are frequently to blame. Stopped vents, loose or leaky vents, and lack of combustion air are common causes of CO. While every technician should learn to look for conditions that can lead to problems, testing is required to verify that a system is operating at safe levels of CO and that there is no CO in the house. Every technician should have an accurate CO tester. Household alarms are not a substitute. While every house with gas or oil appliances certainly should have CO alarms, they are not a replacement for an accurate tool for diagnosis.  I highly recommend a seminar done by Bob Dwyer for COSA (Carbon Monoxide Safety Organization) Make sure and take advantage of the opportunity if you have a chance to attend one of his CO Safety Seminars.

There are many units in Fundamentals of HVAC/R to help explain how to achieve safe, efficient combustion for gas and oil furnaces, including

Unit 37 Gas Fired Heating Systems
Unit 38 Warm Air Furnaces
Unit 40 Gas Furnace Installation, Startup, Checkout, and Operation
Unit 41 Troubleshooting Gas Furnaces
Unit 42 Oil Fired Heating Systems
Unit 43 Oil Furnace and Boiler Service
Unit 44 Residential Oil Heating Installation
Unit 45 Troubleshooting Oil Heating Systems
There are many good web sites for more research on carbon monoxide poisoning. A few are listed below.

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