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• What is NO2 and how does it get in the air?
• What are the harmful effects of NO2?
• What is being done to reduce NO2 pollution?

What is NO2 and how does it get in the air?

Nitrogen Dioxide (NO2) is one of a group of highly reactive gases known as oxides of nitrogen or nitrogen oxides (NOx). Other nitrogen oxides include nitrous acid and nitric acid. NO2 is used as the indicator for the larger group of nitrogen oxides.

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NO2 primarily gets in the air from the burning of fuel. NO2 forms from emissions from cars, trucks and buses, power plants, and off-road equipment.

Effects of NO2

Health effects

Breathing air with a high concentration of NO2 can irritate airways in the human respiratory system. Such exposures over short periods can aggravate respiratory diseases, particularly asthma, leading to respiratory symptoms (such as coughing, wheezing or difficulty breathing), hospital admissions and visits to emergency rooms. Longer exposures to elevated concentrations of NO2 may contribute to the development of asthma and potentially increase susceptibility to respiratory infections. People with asthma, as well as children and the elderly are generally at greater risk for  the health effects of NO2.

NO2 along with other NOx  reacts with other chemicals in the air to form both particulate matter and ozone. Both of these are also harmful when inhaled due to effects on the respiratory system.

• Learn more about Particulate Matter and Ozone.

Environmental effects

NO2 and other NOx interact with water, oxygen and other chemicals in the atmosphere to form acid rain. Acid rain harms sensitive ecosystems such as lakes and forests.

• Learn more about Acid Rain.

The nitrate particles that result from NOx make the air hazy and difficult to see though. This affects the many national parks that we visit for the view.

• Learn more about Visibility and Haze.

NOx in the atmosphere contributes to nutrient pollution in coastal waters.

• Learn more about Nutrient Pollution.

What is being done to reduce NO2 pollution?

EPA’s national and regional rules to reduce emissions of NO2 and NOx will help state and local governments meet the National Ambient Air Quality Standard (NAAQS).

• Learn about how air quality standards help reduce NO2

EPA identifies areas where the air quality does not meet the national NO2 standards. For these areas, state, local, and tribal governments develop plans to reduce the amount of NO2 in the air.

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Calibration Gas for Nitric Oxide, Nitrogen Dioxide, and Nitrogen Oxides

Nitric oxide (NO), nitrogen dioxide (NO2), oxides of nitrogen or nitrogen oxides (NOX) are by products of several processes including incomplete diesel combustion, power plant production & incineration, just to name a few.

There are often questions regarding which calibration gas to use, what is the correct balance gas, and/or what regulator and tubing should be used.

Let us get the information on these calibration gases correct.   

Contact us to discuss your requirements of Nitrogen Dioxide Gas. Our experienced sales team can help you identify the options that best suit your needs.

Here are some recommendations to follow:

• It is not recommended to mix NO and NO2. It is possible but the mixture is highly reactive and unstable resulting in a change in concentrations of the two gases. It is strongly recommended to keep them separated.
• Always use a balance of nitrogen for NO mixtures. An air balance will react with the NO and create NO2.
• Always use a balance of air for NO2 mixtures. The oxygen (20.9%) in the air balance maintains the NO2 stability by providing an excess of oxygen.

Nitrogen dioxide process of dissociation:  2NO2 → 2NO + O2
An excess of oxygen in the mixture will favour recombination.

• NO is typically used to represent NOX in most gas mixtures. EPA Protocol mixtures will list NO certified valve and the NOX as a reference value.
• NO2 cannot be mixed with SO2. The combination is unstable and NO2 can oxidize SO2 to form SO3. Where NO2 and SO2 are required keep them separated.
• For underground mining applications such as coal mining you can mix NO2/CO/CH4/O2 together but the gas mixture shelf life will be based upon the NO2.

Recommendations for regulators and tubing:

• No matter whether the regulator is a flow regulator or pressure regulator ALWAYS use stainless steel
• Use one regulator for each mixture. Don’t mix and match regulators. For example, if you have one mixture of NO/CO/SO2//N2 and one of NO2//Air, you need to purchase two regulators. Label them and only use them for the correct gas mixture. Trace amounts of SO2 could find their way into the NO2 cylinder and contaminate the gas mixture.
• If you are using tubing to deliver the gas mixture, always use Teflon or Teflon-lined tygon tubing.  Do not use standard tygon tubing. The NO2 and NO will adsorb onto the tubing.
• Try to keep the tubing as short as possible. All tubing has a permeation level and these gases are expensive.

Cylinder size:

• Calculate the total volume of gas which you will use in a year. From that determine the best size cylinder which will maximize your efficiency and lower your cost/ litre of the gas.

Today CAC GAS offers a 12 month shelf life for NRC’s (60 litre and 112 litre) and a 36 month shelf life for larger high pressure cylinders (900 litre and litre). The larger the cylinder the lower the cost per litre of the gas.

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