The IFRF provides a sampling probe with a quartz insert for gas sampling in clean gas streams. The quenching tube is quartz lined with the suction in a static position and the sampling line is heated to prevent condensation of sulfuric acid over its entire length. Quartz is recommended because it remains inert to NOx, at high temperatures and short residence times which is not the case for stainless steel. Both stearn-traced and electrically- heated versions are available.