to changes in concentrations of the flue or process gasses application_number US 53976475 A description referring now to the drawings it will be understood that the showings therein are for the purposes of illustrating a preferred embodiment of the present invention and the invention is not limited thereto as may be best seen with reference to fig1 a sampling analyzing system 10 is mounted to a duct or boiler wall 12 to draw process gas 14 from inside the duct and exhaust it back thereto after analyzing the process gas 14 the sampling analyzing system 10 is controlled by a control station 16 which may have an indicator 18 for displaying the measured concentration of a particular element in the process gas 14 such as the concentration of oxygen the sampling analyzing system 10 is enclosed within an insulated enclosure 20 having a door portion 22 which is opened by releasing a known latch assembly 24 to provide ready access to the components therein the sampling analyzing system 10 is mounted to the duct or boiler wall 12 through a pipe nipple 26 which is welded to the duct 12 and which has a pipe mounting flange 28 the enclosure.