3.3 Inspection, Testing & Purging

Quick Answer

Pressure-test with air or inert gas — never oxygen. For ordinary building piping from the meter outlet to each closed appliance shutoff, Massachusetts requires not less than 6 inches of mercury or 3 PSIG for at least 10 minutes with no drop, on a gauge that reads in 0.1 PSIG (or finer) increments, in the inspector’s presence, before concealment. Systems over 1,000,000 Btu/hr jump to ten times working pressure, one hour per 100 feet (cap 24 hours), test pressure not more than 100 PSIG. Find leaks with non-corrosive fluid or an electronic detector, not a match. When you introduce gas, purge large or higher-pressure piping outdoors per NFPA 54 2012 8.3 — the Kleen Energy / 2010 TIA rules Massachusetts still uses — never into a confined space with ignition sources.

---

The PSI bulletin lists Inspection, Testing, and Purging as its own gas-piping bullet. Open 248 CMR 5.00 (effective April 30, 2021) and the PDF: 5.08 is “Modifications to Chapter 8, Inspections, Testing and Purging.” Massachusetts deletes and replaces 8.1.1, deletes 8.1.4 (the model-code test-pressure subsection), deletes 8.1.5.2, replaces 8.1.5.3, deletes 8.2.1, and replaces 8.2.3. It does not rewrite 8.1.2 Test Medium, 8.1.3 Test Preparation, or 8.3 Purging. Those NFPA 54 2012 sections still apply.

Test medium and isolating appliances

NFPA 54 8.1.2 (2012) is the medium rule. The test medium shall be air, nitrogen, carbon dioxide, or an inert gas. Oxygen shall not be used. Oxygen turns a piping system into a combustion accelerator; a later spark or a residue of oil can ignite inside the pipe. Do not substitute fuel gas as the “test” on a new rough — Massachusetts wants a measured pressure test before gas is turned on, except true emergencies (8.1.1(a) as replaced).

NFPA 54 8.1.3 still governs preparation because 5.08 did not delete it. Appliances and equipment that must not see test pressure are disconnected or isolated with blanks, blind flanges, or caps. A 3 PSIG (or much higher elevated) test will wreck appliance controls, regulators, and yellow connectors rated 0.5 PSIG. Isolate at the closed shutoff valve at each appliance — that is also how 248 CMR 8.1.1(a)2 defines the test boundary: from the outlet of the service meter assembly to those closed shutoffs. Expansion joints get temporary restraints if the test thrust requires it. Do not subject a valve to the test if the valve cannot take that pressure.

For CSST, add 248 CMR 5.05(8)(o): no corrosive liquids in testing. Some household soaps attack the tubing and fittings. Use a product made for gas piping. After outdoor jacket is stripped for a joint, re-cover with manufacturer tape after the test (5.05(8)(p)).

Massachusetts pressure, duration, and inspection sequence

248 CMR 5.08(1) is the closed-book core. Inspections also follow 248 CMR 3.00. Unless an emergency exists, gas shall not be turned on and the system shall not be placed in service until:

1. The piping is tested in the presence of the Inspector and approved; and
2. If any part will be enclosed or concealed, that test happens before covering any portion of the system.

For piping from the meter outlet to each closed appliance shutoff:

• Pressure: not less than 6 inches of mercury or 3 PSIG.
• Time: not less than 10 minutes.
• Result: no drop in pressure.
• Gauge: mercury manometer, slope gauge, or equivalent calibrated to read in increments of not more than 0.1 PSIG.

New branches on an existing system are tested to this section if they can be isolated. The connection between new and old piping is then checked with noncorrosive leak-detecting fluid or other methods authorized by this code.

Systems in excess of one million Btu input are a different test:

• Pressure: not less than ten times the proposed maximum working pressure.
• Duration: not less than one hour per 100 linear feet of piping or fraction thereof.
• Maximum duration: 24 hours, no matter how long the pipe is.
• Maximum test pressure: 100 PSIG.

Welded systems pick up still more numbers in 5.05(6) / 5.6.2.2.1 (visual weld inspection; for operating pressure ≤10 PSIG, test the greater of 3 PSIG or ten times operating pressure; between 10 and 70 PSIG, 100 PSIG; duration one hour per 100 feet, min 1 hour, max 24 hours; over 70 PSIG, NDE plus 1.25 times working pressure). Do not apply the 10-minute / 3 PSIG residential test to a welded elevated main.

Undiluted LP piping upstream of the second-stage regulator is tested at not less than 1.5 times that piping’s maximum operating pressure, on a gauge with increments not greater than 0.1 PSIG.

Final inspection (8.1.1(b)): after the rough test, gas may be turned on and appliances tested at normal operating pressure with a non-corrosive leak detection fluid or a properly calibrated electronic leak detector. After successful testing and approval, the inspector attaches a permanent tag in a conspicuous place stating the system has been tested and approved.

Minor repairs and additions (8.1.1(c)) need not be pressure-tested if the work is inspected and connections are tested with non-corrosive fluid, a calibrated electronic detector, or another method acceptable to the inspector.

CSST extra steps (5.05(8)(n)): (1) test before covering as part of the inspection; (2) the licensee performs a second test before connecting any appliance; (3) a tag on the meter or service manifold, signed and dated by the licensed plumber or gas fitter, acknowledges that second test. That licensee tag is in addition to the inspector’s approval tag.

8.1.5.3 as replaced: if there is reason to believe piping is defective or damaged, it shall be tested and inspected, defects and life-safety hazards corrected, and the correction documented in writing to the inspector.

8.2.3 as replaced: immediately after gas is turned on to a tested, inspected, approved new or old system, connected appliances shall be checked for leakage and proper operation. If leakage or a defective appliance is found, shut off that appliance’s gas until repairs are made.

Massachusetts deleted 8.1.5.2, the model-code sentence that named leak-location methods and banned matches. That deletion does not authorize a torch. The methods 248 CMR actually writes are non-corrosive fluid and calibrated electronic detection (plus “authorized” / “acceptable to the inspector” language). An open flame is not on that list.

Purging after the 2010 incidents — NFPA 54 2012 8.3 still applies

On February 7, 2010, indoor natural-gas purging at the Kleen Energy plant in Connecticut killed five workers. NFPA issued TIA 54-09-3 that year; the 2012 edition Massachusetts adopts builds those rules into Chapter 8.3. 248 CMR 5.08 does not modify 8.3, so this is still the Massachusetts purge procedure.

Piping that must be purged outdoors (8.3.1) — if either is true:

• Design operating pressure greater than 2 psig, or
• The piping includes any section meeting Table 8.3.1 size and length.

(CSST EHD 62 is treated as equivalent to nominal 2 inch pipe for this table — typical small-EHD CSST house piping is usually outside the mandatory outdoor table if it is also ≤ 2 psig, which Massachusetts CSST already is because of the 14 inch WC cap.)

For 8.3.1 piping removed from service, residual fuel gas is displaced with inert gas. For 8.3.1 piping placed in operation while full of air, displace air with inert gas first, then displace the inert with fuel gas — do not push a large air/gas interface into a building. The open end being vented or purged discharges directly outdoors, with all of the following:

1. Discharge controlled with a shutoff valve.
2. Point of discharge at least 10 feet from ignition sources, 10 feet from building openings, and 25 feet from mechanical air intakes.
3. The open discharge continuously attended and monitored with a listed combustible-gas indicator that displays 0–100 percent gas by volume in 1 percent or smaller steps.
4. Stop introducing fuel gas when 90 percent fuel gas by volume is detected in the pipe.
5. People not on the purge stay at least 10 feet from the discharge.

Smaller, lower-pressure piping (8.3.2) may be purged indoors or outdoors only if both are true: design pressure 2 psig or less, and the piping is entirely below Table 8.3.1. Even then, 8.3.2.1 is not “open a cock in a boiler room and walk away.” Allowed paths are: discharge outdoors; discharge through an appliance burner not in a combustion chamber with a continuous ignition source; discharge through a burner listed for that purpose with continuous ignition; discharge with a listed combustible-gas detector at the point of discharge, stopping when fuel gas is detected; or purge by the gas supplier’s written procedures. 8.3.3 then requires appliances and equipment to be purged before they are placed in operation.

The safety idea behind every path is the same sentence older 2012 inspection checklists still print: do not discharge purged gas into a confined space or into an area that has ignition sources. The 2010 TIA exists because that is exactly how people died. On a Massachusetts PSI item, a “purge into the mechanical room until you smell gas” answer is wrong for large pipe and reckless for small pipe. Outdoor discharge, attendance, and instrumentation are the 2012 rules the Board left standing when it rewrote 8.1.1.

Put the whole Chapter 8 sequence on one card: isolate appliances → air/inert test (never oxygen) → inspector-witnessed Massachusetts pressure/duration → repair with non-corrosive or electronic methods → CSST’s second licensee test and signed tag if CSST → inspector approval tag → purge per 8.3 → turn gas on → 8.2.3 appliance leak and operation check. Skip a box and the system is not ready for fire.