What dictates the selection of a sensor?
Point sensors used in area monitoring applications are typically diffusion in design. This means that the sensor is not part of an active sampling system that draws the sample to the sensor, but instead relies on diffusion and convection to obtain the sample. That is, the gas will mix with ambient air and diffuse through the sensor’s flame arrestor without requiring a pump or aspirator. Selecting the appropriate sensor for a given application is dictated by the gas or gases to be measured, the background gases present, and the conditions around the sensor’s location. Flammable hazards are measured in the 0-100% lower flammable limit (LFL) or lower explosive limit (LEL) range. Toxic hazards are measured in the low parts per million (ppm) range. Several sensor technologies are available in diffusion designs: catalytic and IR sensors for LFL range monitoring of flammable gases, and electrochemical and solid-state sensors for ppm monitoring.
