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Measuring NOx in Residential & Commercial Boilers & Heaters

Application Note #HV-13-809

Low-NOx Heaters are Becoming More Popular as they Reduce Costs, Help Reduce Ozone and Comply with New Strict Regulations

The air that we breathe and use for combustion processes is comprised of 79% Nitrogen and 20.9% Oxygen. In furnaces and boilers running at higher temperatures (over 2200° F), oxygen reacts with the nitrogen from the air and the fuel utilized to produce NO and NO2 which together are called NOx. These highly reactive gases initiate reactions that produce excess ozone, nitrate particles, and acid rain which are harmful to the environment. Burners with lower combustion temperatures produce less NOx which results in fewer emissions into the atmoshphere. Additionally, the fuel used in combustion has a direct link to the amount of NOx generated. Coal and Oils (No. 2 and No. 6) have the greatest NOx emission in comparison to Butane, Natural Gas, and Propane. Burner manufacturers in HVAC, and industrial processes utilize newer low-NOx technology, providing thermal efficiency improvements of up to 90%, which is why these new types of boilers are becoming increasingly popular and even required in some areas.


Since 1971 the EPA established legislation requiring areas to ensure average annual NOx levels stay low. The chart to the right outlines the sources of these NOx emissions. The majority come from fuel combustion processes which include commercial and residential boilers. For industrial processes such as power plants, emission requirements are much stricter. It is only time until these emissions regulations get stricter for HVAC processes. An integral part of meeting these new compliance goals are low NOx burners and boilers. These newer “Green” Eco-Friendly boilers are all low- NOx and must be periodically tested and maintained to maximize thermal efficiency and provide lower NOx emissions.

Instrument Solution

In order to improve safety and abide by upcoming regulations, high efficiency boilers and burners will soon become common in the residential markets. The installation, repair, and maintenance of this equipment will require specialized tools capable of measuring NOx. The only economic, all-in-one tool is the E Instruments BTU900, capable of measuring O2, CO2, and NOx to ensure any high efficiency burner or boiler is operating at it’s maximum potential.

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