Detecting Mercaptans in Natural Gas Using Length-of-Stain Detector Tubes: ASTM D1988
Updated: Sep 7
Natural gas may require added odorant so a distinctive smell can support leak recognition under applicable conditions. Mercaptans are used in many odorant blends, but concentration measurement and perceived odor intensity answer different questions. This article summarizes ASTM D1988 length-of-stain detector-tube screening without treating it as leak detection or a universal acceptance method.
Understanding ASTM D1988
The ASTM D1988 standard outlines a rapid and straightforward field determination method for mercaptans in natural gas pipelines. The method involves using length-of-stain detector tubes.
Procedure and Significance
ASTM D1988 describes a field method using specified detector tubes and sampling equipment. Results depend on tube selection and range, pump operation, sample point, purge and stabilization, gas conditions, interferences, timing, reading technique, and manufacturer instructions. Testing should be performed by personnel qualified under the operator's procedure. A detector-tube result estimates mercaptan concentration at the sampled location; it does not locate a leak, prove systemwide detectability, or replace odor-intensity testing.
Length-of-stain tubes can provide portable field screening within the selected method's scope and limitations. Record the tube, range, lot or expiration information when relevant, sample procedure, location, operating conditions, result, interferences, and follow-up decision. Do not describe the result as precise, systemwide, or proof that every person will perceive a gas release.
Related Reading
Portable Odorant Analyzer
Detector-Tube Testing Support
Detector-tube results should be documented with the selected tube, stated range, sample procedure, location, time, and relevant gas-system conditions. See Pipeline Operations & Maintenance for field testing and documentation support.
