Natural Gas Odorization Glossary: Technical and Project Terms
Updated: Sep 11
Break-through: During pickling or conditioning, breakthrough is a project-defined downstream response or trend showing that odorant has reached a monitored location. The applicable acceptance and stabilization criteria should be set in the operator-approved plan.
Conditioning: Also called pipeline pickling or pre-odorization, this is controlled odorant exposure used during commissioning or odor-fade remediation. Operators evaluate downstream measurements and trends to determine whether conditions have stabilized; the process does not guarantee elimination of odor fade.
Distribution Line: A distribution line is a pipeline responsible for distributing gas.
Disulfide: A disulfide refers to the structural unit composed of a linked pair of sulfur atoms.
Hydrotest/Hydrostatic Test:A hydrostatic test evaluates pressure integrity using a liquid test medium under an approved procedure. Test medium, pressure, duration, acceptance criteria and applicability depend on the asset and governing requirements.
Injection Rate: Injection rate, also known as odorization rate, is the ratio of the amount of odorant added to a known volume of gas.
Odorant:An odorant is a substance or blend added to gas to provide a recognizable odor. Product composition, properties and handling controls depend on the selected formulation and its current safety data sheet.
Odor Concentration: Gas-in-air odor threshold is the percentage of gas in air at which a tester detects or recognizes the odor under the selected method. It is different from the chemical concentration of an odorant compound in the gas stream.
Odor Fade: Odor fade is the loss of odorant due to physical or chemical processes inside the pipeline or from an underground leak through surrounding soil.
Odor Intensity: Odor intensity is the perceived strength of an odor.
Odor-intensity evaluation performed with an appropriate gas-in-air apparatus or other approved procedure. Method selection, frequency, and recordkeeping depend on the operator’s program and applicable requirements.
Odor Masking: Odor masking is a change or reduce the perceived presence of the gas odorant.
Odorant Concentration: Odorant concentration is the concentration of odorant molecules in a gas, expressed in lbs/MMSCF or ppm.
Odorization: Odorization is the act of adding odorant to gas pipelines.
Odorizer: An odorizer is equipment used to odorize gas.
Pickling: A natural-gas odorization term used interchangeably with pipeline conditioning. It is not acid cleaning, flushing, or scale removal. The objective is controlled odorant exposure, downstream verification, and documented readiness for the operator’s intended service.
Readily Detectable:Readily detectable is language used in applicable odorization requirements and operator procedures. Under 49 CFR 192.625, the relevant instrument determines the percentage of gas in air at which odor becomes readily detectable; the term should not be converted into an unsupported universal response-time definition.
Secondary Containment: Secondary containment is used to contain odorizers and associated storage tanks and vessels.
Sniff Test: Olfactory test with a gas dilution apparatus to meet periodic sampling requirements of 49 CFR §192.625.
