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FAQ's on NOx Filters for CO Sensors


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Healthy Homes are often equipped with Carbon Monoxide (CO) sensors to detect indoor air quality issues related to fuel-burning appliances. Below is information on why you may want to consider also having a NOx - short for oxides of nitrogen, usually nitric oxide (NO), nitrogen dioxide (NO2) and other compounds - filter in tandem with your CO sensor.

Carbon Monoxide Detector

  1. Where does NOx come from?
    NOx compounds can be produced in the high heat of a combustion appliance and become a part of the flue gas stream, along with other combustion products like CO, CO2, water and excess air.

  2. Why do I want to use a NOx filter when I am measuring CO in flue gas?
    A NOx filter will remove many acid gases like NO and NO2 that may interfere with accurate readings on the CO sensor.

  3. Why do I need accurate CO measurements?
    CO measurements are among the most important values used in diagnosing the safety and efficiency of operation for a combustion appliance. There are recommended levels each appliance should meet in its flue gas emissions, as well as standards and regulations to comply with in many jurisdictions. Interference with this measurement can affect both safety and combustion efficiency.

  4. How does NOx interference affect the reading of the CO sensor?
    If NOx is present in the flue gas sample, it will cause the sensor to read CO higher than it should, forcing additional appliance adjustments which may result in reduced efficiency.
Using a NOx filter assures that these potential flue gases will not affect your CO reading, providing the best combination of safety and fuel efficiency.


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FAQ's on NOx Filters for CO Sensors:  Created on February 10th, 2013.  Last Modified on May 5th, 2013


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Don Smith and Associates Inc. dba EnTech Supply represents manufacturers and distributors of safety, environmental, gas detection, and energy saving products.



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