Find the terms by letter
Terms starting with C
Definition
Calibration is a procedure that checks and adjusts an instrument’s settings so that the measurements produced are comparable to a certified standard.
Definition
A chronic effect, in the context of air pollution, refers to the long-term or prolonged impact of exposure to air pollutants on human health or the environment. Unlike acute effects, which occur shortly after exposure and are typically of short duration, chronic effects develop over an extended period of time as a result of repeated or continuous exposure to air pollutants. Chronic exposure to air pollutants can have a range of adverse health and environmental consequences.
Definition
Coefficient of variance is used to measure the variability between sensors. It is calculated by dividing the standard deviation of the sensor during the particular time period divided by the average concentration measured by all sensors of the same model on the same site. A CV of zero represents the perfect agreement between the sensors.
Definition
Collocation is the process of checking the performance of an air sensor by installing and operating a sensor in close proximity to a reference instrument(s). The process by which a sensor and a reference instrument are operated at the same time and place under real world conditions. The siting criteria (e.g., proximity and height of the sensor and the reference monitor) should follow procedures outlined in 40 CFR Part 58 as closely as possible. For example, sensors should be placed within 20 meters horizontal of the reference instrument, positioned such that the sample air inlets for the sensors are within a height of ± 1 meter vertically of the sample air inlets of the reference instrument, and placed as far as possible from any obstructions (e.g., trees, walls) to minimize spatial and wind turbulence effects on sample collection.
Definition
Compensation refers to the adjustment or correction made to the sensor’s output readings to account for the influence of specific environmental factors, such as temperature and relative humidity, on the accuracy of its measurements. The primary purpose of compensation is to ensure that the sensor’s measurements accurately reflect the true concentration of air pollutants, even when these environmental factors vary.
Definition
Completeness measures the amount of data a sensor collects compared to the amount of data that was possible to collect if the sensor operated continuously, without data outages, during a period (e.g., 1 hour, 1 day). A 75% completeness level is a useful criterion to meet as the averaged data is generally representative of that time period. For example, at least 45, 1 minute measurements are needed to make a valid 1-hour average at 75% completeness.
Definition
Correction is the adjustments to sensor measurement data to more closely match the measurement data collected by a reference monitor.
Definition
Cross sensitivity – Other pollutants that interfere with the measurement of the target pollutant.
