Nitrogen dioxide is part of a group of gases called nitrogen oxides. In liquid form, it has a yellow-brown tinge; as a gas, it is reddish-brown. More commonly, it is a gaseous air pollutant, made up of nitrogen and oxygen. Its chemical symbol is NO2, and it has an irritating smell. It is highly reactive and is produced from the burning of fuel. This includes the emissions of vehicles (cars, trucks, buses, motorbikes), power plants, and off-road equipment. In an indoor environment, it can be caused from the burning of fossil fuels, including wood or natural gas. (1,2,3,5)
Nitrogen dioxide is used in a wide range of chemical applications. It is primarily used in the production of nitric acid. It is also used as an oxidising agent, a catalyst, a nitrating agent and in the production of sulfuric acid. In addition, the gas is used to bleach flour, and as an oxidiser for rocket fuel.
Routes of Exposure [2,3,4]
The main route of exposure for nitrogen dioxide is inhalation.
Indoor and outdoor burning of fossil fuels are sources of the gas.
Outdoor sources include the burning of coal and gas at power plants and cars and other vehicles on the road.
Kerosene or gas heaters and gas stoves can cause a build-up of nitrogen dioxide if the area is not properly ventilated.
Nitrogen dioxide poisoning affects a range of systems, including the respiratory system.
Acute Effects 
Severity of symptoms depend on the level and type of exposure.
Acute doses of NO2 can cause problems in occupational settings. Short term exposure can aggravate respiratory conditions, such as asthma. Direct contact with the gas can cause inflammation and burns. If people are exposed to the gas in very high concentrations, it can cause bronchitis, pneumonia, or even death. Often, there are few or no symptoms at the time of exposure, but symptoms develop over time.
Chronic Effects [1,2,3]
Chronic exposure to nitrogen dioxide is toxic to multiple body systems. Long term exposure to the gas can result in the development of respiratory diseases, such as asthma (especially in children), and can also contribute to the susceptibility of respiratory infections. It can also result in an increased allergy response.
~h2First Aid Measures 
- Ingestion: As nitrogen dioxide is a gas, refer to the “Inhalation” section.
- Skin contact: Immediately rinse affected areas with plenty of water, followed by soap and water for at least 15 minutes. Remove all contaminated clothing, footwear and accessories. Do not re-wear clothing until it has been thoroughly decontaminated. Contact a doctor immediately.
- Eye contact: Flush eyes (including under the eyelids), with water for at least 15 minutes. Check for, and remove, any contact lenses (if easily removed). Get medical attention immediately.
- Inhalation: Take victim to the nearest fresh air source and monitor their breathing. Keep the victim warm. If the rescuer believes there are still fumes present, they should wear a mask. If the victim is not breathing, and you are qualified, you may perform CPR with a one-way valve or protective mask. It may be dangerous to perform CPR, due to the dangerous nature of nitrogen dioxide. Immediately contact a medical professional.
- General: Never administer anything by mouth to an unconscious, exposed person.
Exposure Controls/Personal Protection 
Engineering controls: Emergency eyewash fountains and safety showers should be accessible in the immediate area of the potential exposure. Ensure there is adequate ventilation. Use a local exhaust ventilation (with a HEPA-filter dust collection system), or process enclosure, to limit the amount of nitrogen dioxide in the air.
- Personal protection: Safety glasses, protective and dustproof clothing, gloves, an apron and an appropriate mask or dusk respirator. For specifications regarding other PPE, Follow the guidelines set in your jurisdiction.
The Occupational Safety and Health Administration (OSHA) has set an 8-hour time weighted average (TWA) concentration limit for nitrogen dioxide of 5ppm.
Safe Work Australia has set an 8-hour time TWA for nitrogen dioxide of 3ppm.