Ambient Air Monitoring Series

Ambient air measurement at industrial zones, fence-line monitoring

Currently, environmental protection requirements in China are becoming increasingly stringent. Characteristic (special) emission gases in the ambient air of chemical industrial parks must be monitored online. For example, HF in electrolytic aluminum plants, and HCl, H₂S, and NH₃ in the petrochemical industry. The challenges in monitoring characteristic gases in the ambient air of industrial zones lie in the following aspects:

1. The concentration of special gases in ambient air is typically at the ppb level, and most analyzers cannot achieve ppb-level sensitivity.

2. For special gases at ppb levels, such as HF, HCl, HCN, NH₃, H₂S, and BTX, the sampling adsorption (physical and chemical adsorption) of conventional extractive analyzer systems often exceeds the concentration of the measured gas. Extractive analyzer systems are not suitable for monitoring special gases in industrial zones.

3. Sampling points lack representativeness. The purpose of ambient air monitoring in industrial zones is to accurately understand the increase in the overall concentration of special gases in the ambient air of the industrial zone and its surrounding areas after special gases are emitted into the ambient air. Monitoring at a single sampling point is unscientific. Due to the location of monitoring points and climatic wind direction, the detected value at a single monitoring point may be significantly underestimated or overestimated.

The globally recognized preferred method for ambient air monitoring in industrial zones is open long-path remote sensing, to achieve true fence-line ambient air monitoring.

Yousheng Company introduces open long-path remote sensing systems based on laser spectroscopy (TDLAS) and ultraviolet differential (DOAS) technologies:

Laser spectroscopy (TDLAS) technology—Detectable gases: HF, HCl, H₂S, NH₃, etc.

Ultraviolet differential (DOAS) technology—Detectable gases: SO₂, NO, NO₂, BTX, etc.