LP or Natural Gas Fired Appliance Combustion Products in Flue Gas Exhaust
NATURAL GAS COMBUSTION PRODUCTS - CONTENTS: What are the combustion products produced when burning natural gas or LP gas in a heating appliance? What are the normal combustion products and what dangerous combustion products may be produced when a gas fired appliance is not working normally? How much carbon dioxide, carbon monoxide, sulphur dioxide, or nitrous oxide are produced when burning natural gas? Methane gas hazards and hot water tanks - can a hot water heater tank produce methane gas? Methane gas production by methanogens & methanogenesis in water heaters?
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This article lists the components in the flue gas or exhaust gas produced by the combustion of natural gas (and similarly propane gas or liquefied natural gas (LNG) such as when gas is burned in a home heating appliance like a water heater or a heating boiler.
Before it is distributed to consumers, ethane, propane, butane are removed from natural gas. Small quantities of other molecules may be produced during natural gas combustion than those in the “pure” case we listed above.
In the table shown here we list the relative quantities of combustion products produced when burning natural gas. the numbers are pounds produced per million Btus of NG burned:
Table of Combustion & Flue Gas Products in Natural Gas
1 million BTUs is provided in 970 cubic feet of natural gas. (27.4 cubic meters).
MWh = million watt hours.
Normal natural gas combustion: In a practical sense in a home or office building if we are considering a small natural gas appliance such as a water heater, and provided that the equipment and its flue vent connector and chimney area all working correctly and that there is adequate combustion air, once the equipment has warmed up and draft is established, the system is producing CO2 and H2O (in the form of water vapor) and not much else that will be detected by the building occupants.
Imperfect (and unsafe) natural gas combustion, short on Oxygen from too little combustion air or from a chimney problem, will produce CO as well as nitrogen oxides (NOx), organic particulate material, and polynuclear aromatic hydrocarbons (PAH). Incomplete combustion of natural gas may also release un-burned methane CH4 itself.
The reason for the initial versus stabilized- burn CO level spec is that until the appliance heats up combustion is incomplete and higher levels of CO are produced.
The percentage makeup in flue gas from a gas fired water heater will probably not be given as a general overall standard in many references and by most onsite HVAC technicians or inspectors except in theoretical combustion instances because of the wide variability in equipment, vents, and chimneys.
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exposure limits for kerosene & diesel
(Jan 12, 2012) einar gislason said:
what is the allowable breathable levels of both kerosene and diesel when used in a space heater
Einar the exposure limits you seek are described at HEATING OIL EXPOSURE HAZARDS, LIMITS where we include health effects, exposure limits, and MSDS data for heating oil - which is essentially the same as diesel fuel. Because both Benzene and Kerosene are likley to be present together, typically an MSDS gives exposure limits for both as we excerpt from Irving Oil's Kerosene MSDS sheet (citation below):
The ACGIH-TLV exposure limit for Benzene is specified as:
TWA: 0.5 ppm
STEL: 2.5 ppm
The OSHA-PEL for Benzene is specified as
TWA: 10 ppm
STEL: 5 ppm
Ceiling: 25 ppm
The ACGIG-TLV exposure limit for Kerosene is specified as:
TWA: 200 mg/m3
Skin: 100 mg/m3
An OSHA PEL for kerosene is not established.
Many oil companies and others provide an MSDS for Kerosene. An example from Irving Oil is given in the preceding link. - Retrieved 8/19/14 original source https://irvingoil.com/files/03500_Kerosene_-_English.pdf
Excessive intentional inhalation [of kerosene or benzene ] may cause respiratory tract irritation and central nervous
system effects (headache, dizziness).
Question: can an electric water heater produce methane gas?
Hello, I was reading your website about possible odors associated with systems in the home. Is it possible for an electric water heater to produce a methane gas? I have recently verified readings from a hot water line that had methane readings in the flammable ranges. Any input or information would be appreciated.
Reply: an electric water heater does not naturally produce methane gas but there can be other methane gas sources in a building water supply and other odor sources in a water heater or in water supply
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with the water heater or with gas piping in the building, but none of these ought to involve methane induced into the water heater tank interior from the appliance or its fuel piping. And simply heating water does not innately produce methane gas.
An electric, or oil fired water heater does not produce methane gas (CH4). A gas fired water heater indeed uses a fuel gas that includes methane plus an odorant. However a gas-fired water heater might leak LP or natural gas into the air but as there is no under-water gas piping at a conventional water heater I'm doubtful that the fuel gas would be likely to leak directly into the water supply or hot water tank from the heater itself or its gas piping.
Watch out: in some public and private well water supplies methane gas from mining, natural gas drilling and removal from the earth, or other sources may result in high levels of methane gas entering well water.
Watch out: If you do have methane gas in your water supply it could be dangerous, presenting a possible explosion hazard. But if methane is in your water supply, it ought to be present in both hot and cold water, though due to the temperature differences it might be more obvious in one than the other.
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U.S. Energy Information Administration - eia.doe.gov/
U.S. Environmental Protection Agency - epa.gov/solar/energy-and-you/affect/natural-gas.html
At Natural Gas.Org www.naturalgas.org/environment/naturalgas.asp#emission you’ll find a table of combustion products
At geocities.com/rainforest/6847/report1.html is an interesting and detailed though not “neutral” report on the components and contaminants in the combustion of natural gas. You’ll see a long long list of emissions products, but look again – most of the contaminant levels listed are in the picograms.
apvgn.pt/documentacao/iangv_rep_part1.pdf lists the components in natural gas exhaust from vehicles
The Need Project, Manassas, VA: need.org/needpdf/infobook_activities/SecInfo/NGasS.pdf
Kroschwitz, Jacqueline I., and Mary Howe-Grant (eds.). "Gas, Natural." In Encyclopedia of Chemical Technology. 4th ed., vol. 12. New York: John Wiley and Sons, Inc., 1993.
Tussing, Arlon R., & Bob Tippee. The Natural Gas Industry: Evolution, Structure, and Economics. 2nd ed. Tulsa, OK: PennWell Publishing, 1995.
Thanks to careful reader (prefers to be Anonymous) for correcting our data table from erroneous Pounds per Million BTUs Burned to correct Pounds per Billion BTUs Burned, and including a second corroborating resource given just below
NaturalGas.org - a website developed and is maintained by the Natural Gas Supply Association. This site has been created to serve as an informational resource on the many aspects of natural gas. http://www.naturalgas.org/environment/naturalgas.asp#emission
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