Grading the leak: one, two, three. Episode thirty-eight of the Gas Service Animated series.

Not every leak gets the same response. Distribution operations grade every leak by hazard — Grade one, two, or three — and the grade sets what you do and how fast. This system comes from the G-P-T-C guide and the federal pipeline rules, not from NFPA fifty-four — but every service tech needs to read it fluently.

Grade one is an existing or probable hazard to people or property, and it demands immediate, continuous action until it's made safe. Gas you can see, hear, or feel. Any reading at or inside a building. A reading of eighty percent of the lower explosive limit or more in an underground structure gas can migrate through. Four percent gas or more in a manhole or vault. Gas near an ignition source, or a leak that's already lit. Grade one means you don't leave it.

Grade two is recognized as non-hazardous at the moment you find it, but it justifies scheduled repair because it could become a hazard. You don't walk away and forget it — it's repaired on a schedule and re-evaluated on a set interval until it's fixed.

Grade three is non-hazardous now and reasonably expected to stay that way. It's monitored — re-checked at the next scheduled survey — until it clears or is reclassified. Low reading, well away from structures, venting freely.

Here's the part techs get wrong: the grade isn't just the number on the meter. It's the classifying reading — the reading tied to how much gas and how close to a structure. A very high reading far out in open soil can grade lower than a moderate reading right at a foundation. And a paved surface caps the venting, so the same reading grades more hazardous under pavement than under open ground.

How fast you act follows the grade. Grade one, immediately and continuously. Grade two and three get re-evaluated on set intervals — and those intervals are tightening: the twenty twenty-five federal leak rule pulls Grade two re-evaluation from around fifteen months toward six. Always work to your current regulation and your operator's procedure, not to a number from memory.

Read three quick calls. Gas smell plus a reading at the basement wall — Grade one, migrating into a building, make safe now. A steady reading in open soil ten feet from the nearest house, venting freely — likely Grade two, repair scheduled. A trace reading at a fitting in a field, well away from anything, holding low — Grade three, monitor. Same instrument, three very different jobs.

Grading exists so the worst leaks get the fastest hands. For a service tech, the takeaway is simple: know the Grade-one triggers cold — gas in a building, eighty percent L-E-L underground, four percent in a manhole, near ignition — because those are the ones that can't wait.

Grading in one breath. Grade one: existing or probable hazard, act now and don't leave. Grade two: non-hazardous now, scheduled repair. Grade three: non-hazardous, monitor. The classifying reading is gas plus distance plus surface — not just the number. Next: how gas moves underground.