As numerous cars come and go in parking lots, fumes from their exhaust may begin to accumulate. In outdoor parking, these fumes are naturally diluted by the outdoor air and anyone breathing in the general vicinity is typically safe. However, in enclosed or underground parking areas, the fumes become trapped; unless there is a forced ventilation system, the toxic fumes can build up and become hazardous.
To ensure that your parking garage is kept safe, here is a quick cheat sheet on what to look for and tips on designing.
What gases are found in a parking garage?
- Carbon monoxide (CO). Not to be confused with carbon dioxide (CO2), which is the air we exhale, carbon monoxide is the biproduct of a standard gasoline engine exhaust.
- Nitrogen dioxide (NO2) which is the biproduct of the combustion of diesel fuel.
Where should we install the sensors?
- The area of concern is our breathing zone. Therefore, the sensors should be installed around 4 to 6 feet from the finished floor which is the height and which most people breathe from.
- Standard CO and NO2 sensors will have a radius of approximately 50’. If the garage is large enough and a portion of parking area cannot be reached with just a single sensor, add another (or multiple) until all areas are within the 50’ radius of a sensor.
- If you can’t see it, it can’t see you. Take, for instance, an L-shaped garage. If you are on one side of the L and can’t see the other side, even though it might be within the 50’ radius, a new sensor will be required.
How much gas is too much?
- The standard low limit alarm on parking garage fumes is 25 parts per million (ppm) for carbon monoxide and 0.7 ppm for nitrogen dioxide. These levels are not dangerous in short intervals (up to an hour) but can cause discomfort.
- The standard high-limit alarms are set to 100 ppm for CO and 1.5 ppm for NO2. Short exposure could cause discomfort but longer exposure (over 10 minutes) could lead to fatigue and drowsiness and even longer exposure could lead to eventual asphyxiation.
How do we get rid of the gas build up? 
- The best way is with a forced ventilation system that is tied into the gas detection control panel. System can consist of both supply and exhaust fans or and exhaust fan, intake louver/damper system.
- The ventilation system should have one side of the garage installed with the exhaust fans(s) and the opposite side with the supply fans (or intake louver). This will allow for the biggest sweep of dilution air throughout the garage and minimize the amount of dead pockets that do not see any ventilation air.
What should we do to upkeep the system?
- Start with a proper commissioning. Make sure the system works right from the start.
- The ventilation system itself has a standard maintenance routine. Checking the fans motors, pulleys, belts and lubrication are all general maintenance practices in commercial buildings.
- The gas detection system however is much different. The sensors each need to be calibrated every 6-12 months and should be done by a factory trained professional.
The topic of gas detection can be seen as scary and sometimes overwhelming. In fact, any life safety system is. The idea that ‘no news is good news’ can fall in place here and by following some of these simple steps in you gas detection system design, you can ensure that your system is properly installed.
