--- title: Probes and Blowback for Hot, Dusty and Tarry Gas url: https://www.sarveshanalytics.com/learn/hot-dusty-gas-probes-and-blowback.html description: How to sample hot dusty or tarry gas: probe materials, heated and retractable probes, sintered filters, blowback, heated lines. updated: 2026-11-03 source: html --- Learn · Sampling and conditioning # Probes and blowback for hot, dusty and tarry gas Steel plants, kilns, boilers and gasifiers produce gas that destroys a naive sample system in days. A good probe design makes it last for years. Intermediate 3 min read Lesson 7 of 10[Sampling and conditioning](https://www.sarveshanalytics.com/learn/track-sampling.html) Helpful first: [Filters for gas analysers: dust, mist, membrane](https://www.sarveshanalytics.com/learn/filters-and-particulate-protection.html) Quick answer Hot, dusty or tarry gas needs a probe that survives the temperature, a filter at the tip that keeps dust out, and a way to clear the filter, usually automatic blowback with clean air or gas. Heated probes and heated lines keep the sample above its dew point; retractable probes allow service without shutting down. In-situ analysers such as ACCURRA-Zr avoid the sample line altogether. Updated 3 November 2026 · Figures from Sarvesh datasheets **After this lesson you can** - Choose probe materials and heating for hot or tarry gas - Explain how blowback works and when to use it - Know when a retractable probe is worth it - Recognise when in-situ analysis is simpler ## The problem Hot gas can melt or corrode a probe, dust packs into the filter and blocks it, and tar or condensable vapours cool and stick to every cold surface. Water condenses where the sample cools below its dew point. Each of these needs a specific part. ## Probe design - **Material.** SS316 is common; Inconel resists higher temperatures and corrosion; ceramic probes handle the hottest, cleanest-chemistry duties. The SP and SRP probe ranges are offered in SS316, Inconel and ceramic. - **Heated vs non-heated.** A heated probe keeps the filter and sample above the dew point; a non-heated probe suits dry, cooler gas. - **Filter.** A sintered filter at the tip keeps dust out of the line. - **Size and length.** Long enough to reach representative gas; short enough to be rigid and serviceable. ## Blowback A burst of clean, dry air or inert gas, triggered by a timer or when sample flow fails, pushes dust back out of the probe filter into the duct. It is the difference between a probe that runs for a week and one that runs for months. i-Cons and the SP probe series have blowback functions: [How to design a gas sample handling system](https://www.sarveshanalytics.com/learn/how-to-design-a-gas-sample-handling-system.html). **Rule of thumb** If dust loading is more than light, plan automatic blowback from the start. Retrofit is harder. ## Heated lines A heated line carries the sample from the probe to the conditioner above the dew point, so that nothing condenses on the way. SGI-320, the emission monitoring system, combines a probe with auto-blowback, a heated line, a Peltier conditioner and the analysers for NO, SO2, CO, CO2 and O2. ## Retractable probes A retractable probe, such as the SRP-400, can be withdrawn through a valve for cleaning or replacement while the process runs. It is worth the cost where shutdowns are rare or costly. ## When in-situ is simpler If the target is oxygen in hot flue gas, ACCURRA-Zr mounts on the duct with no sample line; its cell sits just outside the wall, fed through a guide tube, with options for high dust and temperatures up to 1400 C: [How a zirconia oxygen analyser works](https://www.sarveshanalytics.com/learn/how-a-zirconia-oxygen-analyser-works.html). For CO and other gases, an extractive system with a robust probe is usually needed. A probe with a filter at the tip. On SP-300 the filter is SS316 sintered, 10 micron, heated, and blown back at 4 to 7 kg/cm2, per the datasheet. **In short** - Match probe material and heating to temperature, dust and dew point. - Automatic blowback keeps a dusty probe running. - Heated lines keep sample above the dew point. - In-situ zirconia avoids sampling for hot flue gas oxygen. ## Check your understanding Answer in your head or on paper first, then open the answer. Recalling an answer teaches more than rereading. **What does blowback do?** A burst of clean gas clears dust from the probe filter back into the duct. **Why use a heated line?** To keep the sample above its dew point so nothing condenses before the conditioner. **When is a retractable probe worth it?** When the probe needs service but the process cannot be shut down. ## Key terms - [Probe](https://www.sarveshanalytics.com/learn/glossary.html#t-probe) - [Blowback](https://www.sarveshanalytics.com/learn/glossary.html#t-blowback) - [Heat tracing](https://www.sarveshanalytics.com/learn/glossary.html#t-heat-tracing) - [In-situ analysis](https://www.sarveshanalytics.com/learn/glossary.html#t-in-situ-analysis) ## Frequently asked questions **What material should a probe be?** SS316 for general duty, Inconel for higher temperature or corrosion, ceramic for the hottest duties. **How often should blowback run?** Set by the dust load; start frequent and relax once the probe stays clean. **Can I sample tarry gas?** Yes with a heated probe, heated line and conditioning matched to the tar, after review of the composition. **What is the difference between SP and SRP probes?** SP are fixed probes; SRP are retractable. ## Related products [ ### SP and SRP sample probes Heated and non-heated probes with blowback, and retractable probes, in SS316, Inconel or ceramic. View SP and SRP sample probes ](https://www.sarveshanalytics.com/sample-probes.html)[ ### SGI-300 / SGI-320 Peltier sample cooler with integrated pump, filter and condensate detector; SGI-320 for emission monitoring. View SGI-300 / SGI-320 ](https://www.sarveshanalytics.com/sample-coolers.html)[ ### i-Cons Smart Peltier sample conditioner with diagnostics, auto blowback and Modbus, in a compact 19 inch cabinet. View i-Cons ](https://www.sarveshanalytics.com/smart-systems-for-gas-analyser.html) ## Where this applies - [Steel plant process gases](https://www.sarveshanalytics.com/applications/steel-plant-process-gas-analysis.html) - [Sample probes SP-100, SP-200 and SP-300](https://www.sarveshanalytics.com/sample-probes.html) - [SRP-400 retractable sample probe](https://www.sarveshanalytics.com/retractable-sample-probe.html) ## Where to go next - [What samples an analyser cannot take: know the limits](https://www.sarveshanalytics.com/learn/what-samples-an-analyser-cannot-take.html)