Chapter 7 Combustion Figure 7-5: Carbon monoxide levels of concern Carbon Monoxide (CO) Levels Death Within 1-3 Minutes Nausea Within 20 Minutes, Death Within 1 Hour Nausea and Convulsions, Death Within 2 Hours Frontal Headaches 1 to 2 Hours, Life Threatening After 3 Hours Maximum Concentration for Continuous Exposure in Any 8 Hour Period Maximum Indoor Air Quality Level Desirable Level Chapter 7—Combustion 7-7 When the acid condenses (at about 150 to 200°F), it adheres to the flue pipe and heat exchanger surfaces in a film and reacts with the iron in the pipe and heat exchanger wall. This creates iron sulfates, the light yellow to rust colored crusty scale you find clinging to the heat exchanger. Scale buildup downgrades efficiency by 1% to 4% over the year. It also blocks flue passages, restricting air flow and increasing smoke and soot. Sulfur levels in heating oil are gradually being reduced, so this will be less of a problem in the future. Carbon monoxide Carbon monoxide, or CO, is a toxic gas that can occur in homes and buildings where combustion by-products are generated, not properly vented and allowed to accumulate. CO is a colorless, odorless, tasteless poison. Carbon monoxide is readily absorbed in the body and can impair the oxygen-carrying capacity of the blood (hemoglobin). Impairment of the body’s hemoglobin results in less oxygen to the brain, heart, and tissues. Even short-term over exposure to carbon monoxide can be critical or fatal to people with heart and lung diseases, and to the young or the elderly. It may also cause headaches and dizziness and other significant medical problems in healthy people. At low concentrations, CO can go undetected and contribute to nagging illnesses, and can compound pre-existing health problems. Figure 7-5. Carbon Monoxide is a result of incomplete combustion due to unburned fuel. During combustion, carbon in the fuel oxidizes through a series of reactions to form carbon dioxide (CO2). However, 100% conversion of carbon to CO2 is rarely achieved under field conditions and some carbon only oxidizes to the intermediate step, carbon monoxide or CO. Carbon Monoxide is usually produced by insufficient combustion air. However, excess air and mismatched oil to air patterns and ratios can also reduce flame temperature to a point where CO is produced. So, adding too much air to clean up a smoky fire can create CO. When any part of the flame is reduced below 1,128°F, CO will be produced. Flame impingement also results in lower flame temperature and CO production. Ambient CO limits (Recommended) 0 ppm. This level is most desirable, but cannot always be achieved due to cigarettes, candles, and appliances such as gas stoves. 1-9 ppm. Normal levels within the home. 10-35 ppm. Advise occupants, check for symptoms (slight headache, tiredness, dizziness, and nausea or flu like symptoms), check all appliances, including the furnace, water heater and boiler, check for other sources including internal combustion engine operation in attached garages. 36-99 ppm. Recommend fresh air, check for symptoms, ventilate the space, recommend medical attention.
NORA Oilheat Technicians Manual
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