Continuous monitoring of Carbon monoxide and Nitrogen dioxide in parking garages

Parking facilities vary in size, design, location and the number and type of cars coming and going. Unlike open parking lots, underground parking or parkades rely on a ventilation system to bring in fresh air and purge the vehicle exhaust buildup inside the building. If the facility is not ventilated properly, it can become a hazardous environment as vehicle exhaust from idling cars and slow moving cars trying to find a place to park collects in the enclosed area. Carbon monoxide is the most abundant of the exhaust fumes, but there is also the possibility for Nitrogen dioxide from diesel powered engines. To provide a safe, breathable parking facility and minimize energy costs associated with the operation of the ventilation system, a hazardous gas detection system is necessary.


Image: Typical Large Parking Garage CO and NO2 Monitoring System



  • The gas detection system operates ventilation systems, on demand controlled​
  • One gas detector provides coverage of up to a 50 ft / 17 m radius with 360-degree coverage​
  • Alternate fuel vehicles that use natural gas, methanol, ethanol, etc. also produce carbon monoxide exhaust


  • Carbon Monoxide (CO)​
  • Nitrogen Dioxide (NO2)​
  • Methane (CH4) or Propane (C3H8)



Parking Garage with VFD Fans Application Mid-size Parking Garage Application Large Parking Garage Application


FCS Multi Channel Controller
cGas-SC Self Contained Controller
CGAS-D Digital Transmitter
CGAS-A- Analog Transmitter
ESH-A Remote Sensor



Where to Mount CO and NO2 Gas Detectors for Diesel Exhaust Applications

For vehicle exhaust applications that include diesel exhaust, Carbon monoxide and Nitrogen dioxide sensor combination gas detectors should be used to monitor the hazardous gas levels in the enclosed space.

Carbon monoxide is about the same density as air and will readily disperse throughout an area where there may be some air movement and activity, remaining in the breathing zone (4-6 ft from the floor). Nitrogen dioxide gas is heavier than air, but when hot, as in exhaust form, it will rise. As the exhaust cools, the gas will dissipate and fall downwards, settling throughout the breathing zone.

In enclosed spaces that have diesel vehicles with bumper height exhaust, the hot exhaust will not reach the ceiling before cooling and settling in the breathing zone. As a result, the Carbon monoxide and Nitrogen dioxide will be present quite quickly in the breathing zone.

In enclosed spaces where vehicles have top-exiting exhausts, the hot exhaust will be higher up and may reach the ceiling, but as the gas cools it will fall downwards and settle into the breathing zone, the space that people are occupying. 

Environments that have vehicle repair pits should have a Nitrogen dioxide gas detector mounted in the pit the gas may pool into the area.

Analyzing the factors in an environment that needs to be monitored to ensure the safest air quality is paramount in understanding where to mount gas sensors. For diesel exhaust applications, you need to understand how the gas acts when it comes in contact with air and consider the type of vehicles occupying the space, where people will be working and how the air movement will affect where the gas may pool or create areas of dead air.

Carbon monoxide and Nitrogen dioxide sensors should always be mounted in the breathing zone. People occupy the breathing zone, therefore that is the area that needs to be monitored for health and safety reasons.