Best Nitrogen Dioxide Detector (NO2 Air Quality in 2024)

Nitrogen Dioxide Detector, NO2 Detector -

Best Nitrogen Dioxide Detector (NO2 Air Quality in 2024)

A nitrogen dioxide (NO2) gas detector is a critical safety device that accurately senses and measures the concentration of NO2 in the air, providing readings in the parts per million (ppm) range. These detectors are essential for personal protection in hazardous gas environments where exposure to nitrogen dioxide may occur. Additionally, NO2 detectors are used to monitor and track the levels of nitrogen dioxide produced by various emissions sources, such as diesel engines, coal-fired power stations, wastewater plants, and manufacturing processes. By continuously monitoring the air and providing real-time NO2 concentration measurements, these gas detectors help protect workers and ensure their safety in industries where nitrogen dioxide is present, while also contributing to the monitoring and control of environmental pollution caused by NO2 emissions.



  • Small and low cost NO2 detectors help with worker safety and emission control.
  • NO2 gas detectors available for less than $399.
  • Portable NO2 detectors ensure that employees and personnel are not exceeding recommended exposure limits.
  • Bump testing and calibration can be forgotten by users.
  • Sensors typically last from 24 to 36 months.
  • NO2 gets confused with NO and NOx.

What is the Best Nitrogen Dioxide Gas Detector?

There are many nitrogen dioxide gas detectors on the market. The reputable brands include the following:

    What Is a Nitrogen Dioxide Gas Detector?

    A nitrogen dioxide gas detector is an instrument used to detect the concentration of nitrogen dioxide in the air. These devices (specifically the Forensics Detectors FD-90A-NO2) have a long battery life, large screen that displays the NO2 concentration, and a belt clip to connect to clothing. In order to protect users, NO2 gas detectors also have LED, vibration, and buzzer alarms.

    Nitrogen dioxide gas detectors are also known as NO2 monitors, nitrogen dioxide sniffers, nitrogen dioxide analyzers, or NO2 gas testers. These names all refer to the same device, a nitrogen dioxide gas detector.

    Who are the Largest Polluters of NO2 Gas?

    The largest polluters of nitrogen dioxide gas (NO2) are typically industrial facilities, power plants, and transportation sources such as cars, trucks, and buses. Agricultural activities, such as the use of fertilizers, can also be significant sources of NO2 emissions. In urban areas, where there is a high concentration of vehicles and industrial facilities, traffic congestion can also contribute to high levels of NO2 pollution. Additionally, wildfires and burning of biomass can release large amounts of NO2 into the atmosphere.

    Does my Gas Oven Emit Nitrogen Dioxide?

    It is possible for a gas oven to emit nitrogen dioxide, although this is typically not a significant source of NO2 gas. Much attention to this topic has been placed due to the recent NYT article.

    Harvard researchers have shown it to be less than 65 µg/m3 which given a conversion of 1 ppb = 1.88 µg/m3, comes to 35 ppb, which is 0.035ppm. 

    For comparison, OSHA has a permissible exposure limit (PEL) for nitrogen dioxide (NO2) of 5 ppm (parts per million) over an 8-hour workday. NIOSH has a recommended exposure limit (REL) for NO2 of 5 ppm over an 8-hour workday. 

    Since nitrogen dioxide is a byproduct of the combustion of natural gas, and can be produced when gas appliances such as ovens are not properly ventilated. So if you are concerned about NO2 accumulation in our home made sure you are turning on your vent fan and opening the kitchen window.

    nitrogen dioxide gas detector

    What Does a Nitrogen Dioxide Meter Detect?

    A nitrogen dioxide detector senses nitrogen dioxide gas and displays the levels in parts per million (ppm).

    It is common to confuse a NO2 meter for a NO meter or even a NOx meter. Please note each gas is significantly different and unique although it may sound similar.

    What Is Nitrogen Dioxide Gas?

    Nitrogen dioxide has the chemical symbol NO2. It is known as a dirty gas with a brownish color. It is an unpleasant gas with an irritating taste and smell. Although NO2 is a pollutant found in emissions, it is also used in industry to make nitric oxide. NO2 gas is very dangerous to human health, hence the need to monitor and check air concentrations.

    Is Nitrogen Dioxide Gas Toxic?

    Yes it is.

    Nitrogen dioxide (NO2) is an air pollutant that is commonly associated with respiratory diseases. According to the American Lung Association, NO2 gas lung effects include: 
    • Inflammation of the airways
    • Cough and wheezing
    • Poor lung function
    • Asthma attacks

    Can I Smell Nitrogen Dioxide Gas?

    Yes, humans can smell nitrogen dioxide gas.

    It is a dirty, polluting gas with a brownish color. It is an unpleasant gas with an irritating taste and smell.

    There are various studies that have investigated the minimum NO2 odor threshold for humans. NO2 can be detected at concentrations as low as few ppm. For example, 0.5  ppm (see here) and 1.5 ppm (see here) have been shown to be the minimum odor threshold for humans.

    However, it is a bad idea to rely on your sense of smell to determine the "concentration" of an aromatic gas like NO2.

    With time, the nose becomes desensitized to the odor - this phenomena is called olfactory fatigue.

    What Are the Different Types of Nitrogen Dioxide Gas Detectors?




    Nitrogen Dioxide Detector for Personal Protection

    The majority of nitrogen dioxide gas detectors are portable units. These are small, battery-powered detectors with a nitrogen dioxide sensor that can be clipped onto your clothes for personal protection. 

    nitrogen dioxide gas detector
    Nitrogen Dioxide Gas Analyzer for Exhaust Gas Monitoring

    NO2 analyzers provide continuous monitoring of exhaust gases for vehicles and combustion engines. Sometimes also used for appliances. These analyzers are typically sold as NOx analyzers, which means NO is also detected and the summation of NO2 and NO is presented as NOx in ppm concentration.

    Nitrogen Dioxide Gas Monitor for Stationary Fixed Wall 

    Wall-mounted units provide continuous protection and warning of nitrogen dioxide gas leaks. These devices are perfect for indoor uses such as power stations, industries, or factories. If the levels of NO2 exceed the preset threshold (i.e., 5ppm OSHA PEL), the unit will provide an LED and buzzer warning.

    fixed wall mount H2S monitor

    How Does a NO2 Gas Sensor Work?

    A nitrogen dioxide gas detector is composed of electronics and an NO2 sensor. The gas sensor converts the detected nitrogen dioxide level to an electronic signal for microprocessor analysis. After receiving the sensor signal, the unit displays the NO2 concentration. If the measurement exceeds the pre-set NO2 alarm value, the alarms are triggered.


    Sensor Technology



    Nitrogen Dioxide (NO2)

    NO2 Electrochemical Gas Sensors

    The gas reacts with a working electrode, triggering an electrochemical redox reaction. The generated current is proportional to the detected gas level.

    • Small, fast response, & cheap
    • Easy to integrate with electronics
    • Immediate ON
    • Limited life from 24 to 36 months
    • Influenced by temperature and humidity
    Nitrogen Dioxide (NO2)

    NO2 Semiconducting Metal Oxide Gas Sensors

    Ozone molecules interact with a film of metal oxide material, where surface redox reactions take place. A power-law relationship transpires between the ozone concentration and conductivity of the sensor.

    • Long lifetime, lasting over five years
    • Very sensitive
    • Low cost and simple construction
    • Robust
    • Cross- sensitivity to oxidizing gases, such as Cl2 and O3
    • 10-minute warm-up time
    • Influenced by temperature and humidity

    What Do Nitrogen Dioxide Gas Sensors Look Like?

    Below is an image of an electrochemical nitrogen dioxide gas sensor.

    nitrogen dioxide gas sensor

    Below is an image of semiconducting nitrogen dioxide gas sensor from Spec Sensors and their development kit items.

    spec sensors nitrogen dioxide


    What Are Safe Nitrogen Dioxide Gas Levels?

    Various government agencies have recommended gas exposure limits, examples can be seen below:


    Recommendation / Requirement

    National Institute for Occupational Safety and Health (NIOSH)

    NIOSH Recommended Exposure Limit (REL):

    1 ppm, 10-minute ceiling

    Occupational Safety and Health (OSHA)

    5 ppm average over 15 minutes (Permissble Exposure Limit)

    American Conference of Governmental Industrial Hygienists (ACGIH)

    3 ppm average over 8 hours & 5 ppm as a short term exposure limit

    What Is a Nitrogen Dioxide Gas Detector Used For?

    Nitrogen dioxide gas is used in a variety of manufacturing and industrial processes, hence the requirement for accurate detection and human exposure limits. NO2 gas applications include:

    • NO2 gas to make nitric acid: NO2 is used to make HNO3, often called nitric acid. This chemical is used to produce various nitrogen compounds to create chemical fertilizers, explosives, and other useful substances.
    • NO2 gas as a sterilization agent: NO2 is a sterilization gas used for medical and dental instruments. Used in a chamber-based system, advantages includes room temperature operation, low concentration, fast microbicidal activity, and low residue
    • NO2 gas as a bleaching agent: NO2 is used as a bleaching agent, similar to chlorine and bromates. These chemicals are strong oxidizers. 

    Is Nitrogen Dioxide Gas Flammable?

    Not it is not.

    Is a Nitrogen Dioxide (NO2) Gas Detector the Same as a Nitric Oxide (NO) Detector? 

    No it is not.

    Most of us know nitric oxide gas (NO) as "laughing gas." Nitric oxide gas is very different from NO2. NO gas is used for pain relief by dentists and medical personnel to sedate patients undergoing medical procedures.

    There are specific NO sensors used for NO detection.

    What Is the Difference Between a Nitrogen Dioxide (NO2) Gas Detector and an NOx Gas Detector?

    The term NOx refers to nitrogen oxides, which include NO2 and NO. Although NO is very different from NO2, it does react with oxygen or ozone in the air to form NO2, hence the term NOx. The main pollutant is NO2. However, NO in the environment may transform into NO2.

    Other oxides of nitrogen include NO3 (nitrogen trioxide), N2O (nitrous oxide), N2O4, and N2O5, but are not as readily found as NO and NO2.

    NOx Gas Detectors and NOx analyzers are specifically made products to detects emissions from combustion.

    Do NOx Gas Sensors Exist?

    There is no such thing as a NOx sensor. NOx is a "lazy" term to describe both NO2 and NO. Therefore, when one uses NOx it means at least NO2 and NO. Therefore, there is no NOx gas sensor that can detect both with the same single gas sensing element. Typically, a NOx detector employs both a NO2 and NO gas sensor.

    How Do I Select a Nitrogen Dioxide Detector?

    To select the best personal protection nitrogen dioxide gas detector, follow this simple guide:

        • What is my budget and operating cost budget?
        • Do I need advanced functions such as data-logging or Bluetooth?
        • Do I need specific accreditations with the monitor such as a NIST traceability calibration?
        • Do I require a belt clip for attaching the device to my clothes?
        • Do I need after-sales support, USA headquarters, or fast calibration services?

      What About Atmospheric Nitrogen Dioxide Monitoring?

      Most of the nitrogen dioxide gas meters on the market are based on electrochemical detection sensors. These are used for personal protection and alarm in the ppm range for OSHA and NIOSH limits.

      For atmospheric and environmental NO2 measurements, sensitivity in the parts per billion (ppb) range is required. These systems are much more expensive and can exceed $10,000. These analyzers employ chemiluminescence detection methods. 

      Below is a picture of the Ecotech NO2 Analyzer that measures NO, NO2, and NOX in ambient air with a lower detection limit of 0.4 ppb and a range from 0 to 20 ppm.

      nitrogen dioxide gas analyzer

      How Long Does a Nitrogen Dioxide Detector Last For?

      Nitrogen dioxide gas detectors incorporate small electrochemical sensors that usually last between 24 and 36 months.

      There are NO2 gas sensor that employ semiconducting metal oxide technology and last over 5 years. Unfortunately, they are not as specific as electrochemical sensors. Some sensor and detectors are here:

      How Do I Test My Nitrogen Dioxide Detector?

      The best way to test your nitrogen dioxide gas detector is to expose it to a known gas source. Generally referred to as bump testing, this is a good practice to perform daily. Frequent testing is especially important in personal protection NO2 applications where safety is paramount.

      What Is a Nitrogen Dioxide Bump Test?

      • Bump testing NO2 gas is a procedure where the user exposes the detector to a small amount of “blast” target gas to ensure the device operates and alarms as programmed.
      • The function of this NO2 gas test is to verify proper operation and build user confidence, particularly in hazardous applications.
      • It is recommended to NO2 bump test when first purchased, with subsequent testing every week. If using in LIFE-THREATENING and / or DANGEROUS applications, bump test daily.
      • Nitrogen dioxide bump test gas can be found here.

      What Is Nitrogen Dioxide Detector Gas Calibration?

      Nitrogen dioxide gas detector calibration is the technical task of adjusting the monitor to a more accurate gas reading. Over time, the sensors on the device will degrade or produce drifting readings. We suggest calibrating your NO2 detector every 6 to 12 months, the typical time period for gas detectors.

      Gas calibration is a technical task that requires certain key pieces of equipment. These include a calibration gas bottle, gas regulator, tubing, and calibration cap fitting. You need to communicate with the manufacturer to determine the recommended calibration gas concentrations and mixtures. For the Forensics Detectors NO2 gas monitors, we recommend the calibration gas here.
      Be attentive and calibrate daily if:
      • The user employs the device as an analytical tool where accuracy is paramount.
      • The device is used in an extreme environment (temp and humidity extremes create sensor drift).
      • The user is performing an imminently dangerous application. Bump testing fails. In this case, you must calibrate to make sure the sensors and monitor operate properly.
      • The NO2 gas detector alarms in the fresh air. This could mean that the sensor has drifted past an alarm set-point.
      • Calibration and bump testing are mandatory because injury or death can occur if the device fails. Take it very seriously.
      Also, it is prudent to have a calibration schedule that the owner or employees strictly follow. See gas calibration here.

      How Do I Take Care of My Nitrogen Dioxide Gas Detector?

      • Store your NO2 gas detector at a normal room temperature.

      • Store it away from electromagnetic or magnetic sources, such as phones.

      • Store it in a clean environment with no dust or particles.

      • Store away from any exhaust gas, concentrated vapors, and harsh chemicals.

      • Clean the casing of your detector with a damp cloth.

      • Store it in a stable place where there are no vibrations or continuous shaking.

      How Do I Properly Use a Nitrogen Dioxide Gas Detector?

      When operating an NO2 gas detector, there are some important tips to consider. After reading your product manual, be sure to keep these tips in mind:

      • Turn ON the NO2 gas monitor in the fresh air. 

      • Ensure the NO2 gas monitor is within its calibration period.

      • Ensure the NO2 gas monitor has been bump tested and validated as operational. 

      • Check the alarm set-points. Set your alarms as desired (some units may not have adjustable alarms).

      • If performing analytical measurements, keep the unit stationary. Ensure humidity and temperature are also tracked and are as constant as possible.

      Final Words

      Nitrogen dioxide (NO2) is a highly poisonous and toxic gas that poses significant health risks. It is primarily emitted during combustion processes, with diesel engines being a major contributor. Additionally, NO2 finds use in various applications such as sterilization, industrial processes, and manufacturing. Due to the hazardous nature of nitrogen dioxide, personal protection in environments where this gas is present is of utmost importance. NO2 gas meters play a crucial role in ensuring the safety of workers in industries that involve the use of nitrogen dioxide, as well as those working with emissions or in sterilization and bleaching processes. These gas detectors continuously monitor the air, providing real-time measurements of NO2 concentrations and alerting users when levels exceed safe thresholds. With NO2 gas detectors being affordable, costing less than $400 per unit, industries dealing with this toxic gas should prioritize the well-being of their employees by investing in these life-saving devices. Implementing NO2 gas detectors not only protects workers but also contributes to the monitoring and control of environmental pollution caused by nitrogen dioxide emissions.

      About The Author

      Dr. Kos Galatsis ("Dr.Koz") is the President of FORENSICS DETECTORS, where the company operates from the scenic Palos Verdes Peninsula in Los Angeles, California. He is a subject matter expert on gas sensor technology, gas detectors, gas meters, and gas analyzers. He has been designing, building, manufacturing, and testing toxic gas detection systems for over 20 years.

      gas detector expert

      Every day is a blessing for Dr. Koz. He loves to help customers solve their unique problems. Dr. Koz also loves spending time with his wife and his three children going to the beach, grilling burgers, and enjoying the outdoors.

      Read more about Forensics Detectors here.

      Phone: +1 424-341-3886