Abstract
Effects of (1) sizes and positions of target gas distributions, (2) diameter and divergence of IR beam used for measurements, and (3) the types of reflection mirror upon signal intensities in the open-path FT-IR measurements were examined in detail experimentally and with theoretical simulations. These factors were found to affect only a little when the target gas distribution is much larger than the IR beam diameter. On the other hand, when the target gas distribution is similar to or smaller than the IR beam size, signal intensity was found to be dependent on these factors in complicated manners. In such cases, it is highly difficult to get quantitative information of the target gas.
