How often are CEMs normally zeroed and spanned?

CEMs, or Continuous Emission Monitors, play a critical role in ensuring that emissions are accurately measured to comply with environmental regulations. The process of zeroing and spanning these monitors is essential for maintaining their accuracy and reliability over time.

Zeroing refers to calibrating the instrument to read zero when no emissions are present, while spanning involves calibrating the monitor to read accurately across the measurement range. These procedures are commonly recommended to be performed daily to ensure that any drift in the readings is corrected and that the data remains valid throughout operational hours. Frequent calibration is particularly important because emissions can fluctuate, and even small inaccuracies in monitoring can lead to significant compliance issues or environmental concerns.

In contrast, options such as weekly, monthly, or yearly intervals may not provide the necessary precision needed in environments with constantly changing emissions, which is why daily calibration practices are standard in many regulatory frameworks. Therefore, the emphasis on daily zeroing and spanning helps maintain the integrity of emissions monitoring, ensuring regulatory compliance and protecting air quality.