Nitrogen Dioxide
NO₂Nitrogen dioxide (NO₂) is a reddish-brown gas with a sharp, biting odor that forms during high-temperature combustion and is present in diesel vehicle exhaust, power plant flue gases, and welding operations. The gas is highly toxic to the respiratory system and is a precursor to ground-level ozone and fine particulate matter. OSHA PEL is 5 ppm ceiling with IDLH at 20 ppm. NO₂ detection is essential in locations where diesel vehicles idle, maneuver, or load/unload, including parking structures, tunnels, loading docks, bus depots, warehouses, industrial facilities, and indoor environments where combustion equipment operates. Modern facilities typically deploy dual gas CO + NO₂ monitoring to ensure full coverage of both gasoline and diesel exhaust risks. This combined approach provides a more accurate picture of air quality and ensures ventilation systems activate appropriately.
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Key Information
Essential safety and exposure information for Nitrogen Dioxide
Health Effects
- Highly toxic, corrosive respiratory irritant and becomes hazardous at very low concentrations
- NO₂ reacts with moisture in the lungs to form nitric and nitrous acids, which can damage airway tissues
- Causes symptoms such as coughing, difficulty breathing, chest tightness, fluid buildup and respiratory failure even when exposure is brief
Common Sources
- Diesel exhaust
- Boilers
- Turbines
- Kilns
- Industrial burners
- Gas stoves and ovens
- Unvented heaters
- Fireplaces and wood stoves
- Welding and cutting torches
Exposure Limits
- OSHA PEL
- 5 ppm
- NIOSH REL (STEL)
- 1 ppm
- NIOSH IDLH
- 20 ppm
- ACGIH TLV (TWA)
- 0.2 ppm
- ACGIH TLV (STEL)
- 1 ppm
Regulatory Status
- Nitrogen dioxide (NO₂) gas detection is required by multiple building and mechanical codes across the U.S. and Canada. Both the International Mechanical Code (IMC 404.1) and the National Energy Code of Canada for Buildings (NECB A‑5.2.3.4(1)) mandate the use of CO and NO₂ sensors in enclosed parking garages, maintenance bays, dealerships, and similar vehicle‑exhaust environments to enable automatic ventilation control. CO is typically regulated using time‑weighted thresholds, while NO₂—because of its significantly higher toxicity—is governed by much lower short‑term limits. Industry standards such as ACI further support these requirements by defining sensor placement, quantity, and integration with fan control systems.
Detection Requirements
- Sensor Technology
- Electrochemical
- Sensor Detection Range
- 0-10 ppm
- Alarm Setpoints
- Low 0.7 ppm, Mid 1.00 ppm, High 1.5 ppm
- Mounting
- Breathing Zone 4-6 ft / 1.2-1.8 m from the floor
Detection Solutions
Sensors and detectors for Nitrogen Dioxide monitoring
LPT Low Power Transmitter
Single channel, analog gas detector for enclosed parking facilities, recreational facilities, oxygen depletion applications.
cGas Detector Analog Transmitter
Single channel, analog gas detector with Plug & Play Smart Sensor Technology.
cGas Detector Digital Transmitter
One or two channel Modbus® or BACnet® gas detector with flexible customization options and Plug & Play Smart Sensor Technology.
cGas-SC Self-Contained Controller
A self contained controller with up to 3 gas channels, Plug & Play Smart Sensor Technology and configurable logic control and priority settings. Offers superior user customization and reliable gas detection performance for monitoring many gases.
CXT2 Explosion Proof Transmitter
Reliable, accurate monitoring of toxic or combustible gases in potentially explosive and harsh environments, including hazardous-rated areas.
FCS Multi Channel System Controllers
High performance controller with logic and priority settings for monitoring toxic, combustible and refrigerant gases with versatile control functionality. Available with Modbus® or BACnet® communication with BAS, supports 4-20 mA and Modbus® driven VFDs.
RSH-24V Remote Strobe & Horn
Two alarm features in one safety device, mounting fixture not included. Available in 3 different lens colours, combines a visual and an audible alarm feature into one compact, low profile device.
Related Gases
Other Toxic Gases we detect