Update: 2019-11-20 16:21 Source: LUFTMY
There are many types of air quality monitors available on the market, but which one is the best choice to measure the concentration of gaseous air pollutants?
Such air quality monitors fall into two categories: sampling monitors and field monitors (" field "=" in the original location "). The sampling monitor utilizes a manifold through which the air to be analyzed is pumped. A small amount of air sample is then sealed into a chamber where its molecular content can be analyzed. The analytical method varies according to the optical properties of the molecules. For example, uv is commonly used to detect SO2 fluorescence, while gas correlation is used to detect CO. Methods vary widely, so there are usually specific instruments for each specific type of molecule.
Instead, field monitors can detect molecular concentrations in the natural environment without pumping and sealing in any cell. The detection is carried out along an open optical path, in which all the existing molecules contribute to the characteristic absorption of some wavelengths. Each type of molecule has its own absorption mode, so that a single monitor can detect the concentration of many different types of molecules.
Therefore, when designing environmental monitoring system, should we choose sampling or field monitor?
From the perspective of detection characteristics and data quality, the results of the two methods are basically the same.However, the premise is that all maintenance activities are carried out according to the manual.To this extent, sampling monitors require more frequent and expensive maintenance than on-site monitoring systems.In practice, you often see that the maintenance scheme is not maintained, resulting in suspicious monitoring results or even complete loss of data when trying to use the sampling monitor.
In contrast, field monitors require little maintenance.Therefore, in the long run, they can usually produce more reliable data at a higher capture rate than the sampling monitor.Admittedly, a field monitor is usually more expensive than one or more sampling analyzers, but the total cost of ownership, including maintenance, is good for the field monitor.
Compared with the sampling monitor, another advantage of the in situ monitor is the automatic averaging along the optical path. Therefore, the monitoring results represent the whole area to be monitored, not only a single point of the air inlet of the sampling monitor.
To sum up, the best choice of air quality monitor for detecting gas pollutants is usually on-site monitor.