Gas Odor Call Response

Purpose

Everything in the first four minutes of a gas odor call happens before anyone diagnoses anything. The customer leaves the building on foot, touches no switch and no phone inside, and calls the gas operator from outside. The shop's job is to make that happen on the phone, then take a controlled handoff from the operator and do the survey properly. This procedure exists because the failure mode is not a missed leak, it is a well-meant instruction: a dispatcher who says a tech is on the way in twenty minutes has just told a family to sit inside and wait.

Scope

Covers the response to a reported gas odor at a residential property, from the intake call through evacuation, operator handoff, instrument survey of the customer-owned piping and appliances, and either repair or red-tag.

It does NOT cover the operator's side of the meter, which belongs to the gas utility and is never worked by the shop. It does not cover the routine pressure test of house piping, which the gas line pressure test SOP owns and which this procedure hands off to once a leak is isolated. It does not cover carbon monoxide complaints with no gas odor, which are a combustion problem rather than a fuel leak.

Roles and the handoff

The handoff that must not blur: the gas operator clears the atmosphere and owns their own facilities; the shop owns everything downstream of the meter. A tech who starts surveying before the operator has released the scene is standing in an atmosphere nobody has measured.

Procedure

1. Give the evacuation instruction on the phone, in specific words, before anything else. Everyone leaves the building now, on foot, including pets. No light switches, no thermostats, no garage door opener, no doorbell, no phone used inside, no vehicle started in an attached garage, no candle and no match. Call the gas operator's emergency number and 911 from outside, well away from the building. Acceptance: the caller states they are outside and the operator has been called, and the dispatcher logs both times. Wrong looks like "we can have someone there in twenty minutes", which reads as permission to wait indoors.

2. Do not promise an arrival that competes with the operator. The gas operator responds to odor calls at no charge and usually faster than a service truck, and they carry authority to shut and lock the meter. Acceptance: the caller understands the operator comes first and the shop follows. Wrong looks like a customer cancelling the utility call because the plumber is coming, which is the single most dangerous thing a dispatcher can cause.

3. On arrival, park and approach as if the atmosphere is flammable, because you have not measured it. Park upwind and away from the structure, do not pull into the driveway near the meter, leave the engine off, and approach on foot. Confirm the occupants are out and accounted for and that the operator has been called or is on site. Acceptance: occupants outside, headcount confirmed, operator status known before you go near the building.

4. Do not enter until the operator has released the scene, and enter with an instrument, not a nose. Natural gas is flammable in air from roughly 5 percent to 15 percent by volume and propane from roughly 2.1 percent to 9.5 percent, which means a strong odor can sit either side of ignitable. Odor also fades: mercaptan can be scrubbed by soil and rust, so a faint smell does not mean a small leak. Acceptance: operator handoff received, combustible gas indicator bump tested that day, and background read outside at 0 before entry.

5. Survey with the gas density in mind, because it decides where to look. Methane is lighter than air and collects high, at ceilings, in attic spaces and along the top of chases. Propane is heavier than air and collects low, in basements, crawls, floor drains, sumps and pits. Acceptance: readings logged at ceiling and floor level in each room for methane and propane respectively, plus every appliance connection. Wrong looks like a propane survey run at nose height, which is exactly the elevation the gas is not at.

6. Read the instrument in the units it reports and convert deliberately. A combustible gas indicator reports percent of the lower explosive limit, so 20 percent LEL on methane is about 1 percent gas by volume, since methane's LEL sits near 5 percent. Acceptance: each reading logged as percent LEL with its location. An instrument calibrated on methane does not read propane at face value, so apply the maker's response factor or calibrate to the gas you are surveying, and note which you did.

7. Isolate by section rather than hunting the whole house at once. Close appliance shutoffs one at a time, starting with the appliance nearest the strongest reading, and watch whether the reading falls. Acceptance: the section carrying the leak identified by a falling reading with a valve closed. Wrong looks like closing everything at once, which proves only that the gas came from somewhere in the building.

8. Pinpoint with a listed leak-detection solution or an electronic detector, never with a flame. Work joint by joint on the isolated section, including the flex connector, the union, the sediment trap and the control valve inlet. Acceptance: a specific joint or component named with bubble growth or a detector response. Wrong looks like a report saying "leak at the range", which the next tech cannot act on and the customer cannot understand.

9. Where the leak is in concealed piping, stop rather than chase it. A reading that peaks at a wall cavity, a floor register or a slab penetration with no appliance nearby means the leak is in buried or concealed pipe. Acceptance: house gas shut and locked at the point the operator or the code allows, red tag applied, and the finding handed to the lead the same day. Wrong looks like opening a wall to follow a smell, which puts a tool and a spark into the space with the highest concentration in the building.

10. Repair, then prove the whole system rather than the joint you touched. Repair to the material and method the code allows for that pipe, then hand off to the gas line pressure test SOP for a full test at the pressure and duration your jurisdiction sets under NFPA 54, the National Fuel Gas Code, in the edition your authority having jurisdiction has adopted. Acceptance: a passed test recorded, not a bubble check on one fitting. Wrong looks like a repaired union and no test, because the leak that generated the odor is often not the only one on an aging system.

11. Relight, verify combustion, and leave a written record with the customer. Relight each appliance per its instructions, confirm stable flame, and check for carbon monoxide at each appliance with a personal monitor at your breathing zone; the OSHA permissible exposure limit is 50 ppm as an 8 hour time weighted average (29 CFR 1910.1000 Table Z-1). Acceptance: all appliances lit and stable, monitor at background. If anything is left off, the customer gets the red tag and a written notice naming what is off, why, and what has to happen before it goes back on.

When the system stays off

Some of these calls end with gas to the house shut and nothing repaired, and that has to be a normal outcome rather than a failure. Concealed leak in buried or under-slab piping: shut, tag, and scope a re-route or replacement, because that is days of work and not a same-visit fix. Appliance so old the parts are unavailable: shut its valve, cap the drop, and say plainly that the appliance is done. Customer refuses the shutdown: you cannot leave a leaking gas system live on a request, so the notice is written, the operator is informed, and the shop's obligation is documented rather than argued. The odor is real and the survey finds nothing: do not close the ticket clean. Re-survey with the operator's instrument if they are still on site, ask about odorant sources that mimic gas, and where nothing is found, say so in writing with the readings, the date and the recommendation to call again immediately if it returns.

The record this produces

One emergency response record per call, on the property record:

• Time the evacuation instruction was given, and confirmation the caller was outside
• Whether the gas operator was called, by whom, and when they released the scene
• Instrument used, bump test date, calibration gas, and any response factor applied
• Every reading as percent LEL with its location and elevation
• Which appliance valves were closed and how the readings responded
• The component or section identified, and photographs
• Repair performed and the pressure test result, or the red tag with what is off and why
• Relight confirmation and the carbon monoxide check at each appliance
• Written notice left with the customer, and their signature where they declined work

The lead reads it the same day. The operator may ask for it. Months later it is the only proof of what the shop told the customer and when.

Worked pass: odor at a 1970s house on natural gas

Intake at 7:12 pm: caller reports a rotten egg smell in the hallway, stronger than usual, no appliance obviously running.

• Step 1: evacuation script given verbatim at 7:12 pm; caller confirmed outside with two children and a dog at 7:14 pm; operator emergency line called at 7:15 pm.
• Steps 2 to 3: tech arrived 7:41 pm, parked across the street, occupants accounted for, operator on site and working the meter set.
• Step 4: operator released the interior at 8:05 pm. Combustible gas indicator bump tested that morning, background read 0 percent LEL at the driveway.
• Steps 5 to 6: ceiling-level survey for methane. Kitchen range connection 0, dryer connection 4 percent LEL, water heater 0, hallway baseboard near an interior wall 22 percent LEL, which on methane's roughly 5 percent lower explosive limit is about 1.1 percent gas by volume. The peak was not at any appliance.
• Step 7: closed the dryer, range and water heater valves one at a time; the hallway reading did not fall with any of them.
• Step 8 and 9: STOPPED. With no appliance accounting for the peak and the highest readings following the interior wall line rather than a fixture, the leak was in concealed piping. Stop rule taken at step 9: house gas shut and locked at the point the operator directed, red tag applied to the meter set, nothing opened, and the lead called from the driveway at 8:26 pm.

The follow-up scope, quoted the next morning, was to abandon the concealed branch feeding the old wall furnace stub and re-route the run exposed through the basement, then full-system test under the gas line pressure test SOP before relight. The customer stayed off gas for two nights, which the written notice had told them plainly on the night, along with the 22 percent LEL reading and where it was taken. The dryer's 4 percent LEL reading was repaired at the same visit, and it is worth naming why it was not the answer: it was real, it was small, and it was nowhere near the peak. A tech who stopped at the first positive reading would have fixed a connector and left a wall full of gas.

References

• NFPA 54 / ANSI Z223.1, National Fuel Gas Code, in the edition your authority having jurisdiction has adopted, for piping, repair and test requirements downstream of the meter
• Your gas operator's emergency response procedures, which govern their side of the meter and their release of the scene
• Combustible gas indicator manufacturer documentation for bump testing, calibration gas and response factors between methane and propane
• 29 CFR 1910.1000 Table Z-1 for the carbon monoxide permissible exposure limit during the relight check
• See related: the gas line pressure test SOP and the water heater changeout SOP