Gas appliance, heater, piping & control safety hazards:

Descriptions and photographs of unsafe gas piping, regulators, or controls on heating systems, indications of unsafe or improperly operating gas appliances, gas meters, and other gas installation defects.

This document also provides free sample draft home inspection report language for reporting defects in oil and gas piping at residential properties.

Immediate LP Gas & Natural Gas Safety Hazards

Immediate LP or natural gas safety hazards: if there is evidence of an LP or natural gas leak at a building, gas odors, for example, you should:

• Do not do anything that is likely to cause a gas explosion, such as lighting a match, operating an electrical switch, or even using a telephone in the building
• Leave the building immediately and keep a safe distance away - 100 feet or more.
• Notify other building occupants of the safety concern
• Contact the local gas company and/or fire department

Heating equipment which the inspector (or building occupant or manager) judges to be an immediate life safety hazard should be shut down and appropriate emergency services called.

See GAS LEAK DETECTION, LP / NG for leak detection procedures and alternatives.

Unsafe heating appliance conditions caused by backdrafting are discussed

at BACKDRAFTING HEATING EQUIPMENT.

General safety warning: improper installation and even improper inspection and testing methods involving natural or "LP" gas can involve dangerous conditions and risk fire or explosion. If you smell gas you should leave the building immediately and should do so without doing anything that could create a spark such as operating a light switch or telephone.

Watch Out: From a safe location, call your gas company's emergency line and/or your fire department.  The text provided here is a working draft and may be incomplete or inaccurate. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Also see OIL TANK PIPING & PIPING DEFECTS.

NOTICE: while example report language is provided here, reproduction of this or any of our web pages or their contents at other websites or in printed documents for sale is prohibited.

Examples of Easily-Detected Gas Leak Hazards

Gas Odors: A gas leak can be indicated by gas odor such as in the utility area near appliances or elsewhere in the building. Leave the building and call for help from a safe location.

Photo at left: coated stainless steel gas appliance connector used for appliances & heating equipment.

Watch out when moving gas appliances: older flexible tubing may be thin-wall, corroded, damaged, and easily torn or caused to leak. Shut off the gas supply before moving appliances to minimize the hazard.

Here is a list of examples of other immediate LP gas or natural gas leak safety hazards that might be detected using a TIF8800™ Combustible Gas detector or using a soap solution and bubble testing:

• A gas leak in gas piping - check particularly at piping joints or in areas where there is apparent damage, corrosion, possible pin holing in the piping.
• A gas leak at the gas meter equipment. Check at meter seams and at piping connections.
• A gas leak at the gas control valve.
  • A gas leak may be found at the appliance pilot and temperature control knobs at control top.
  • A gas leak may be found at the center seam along the RH side of the control. (often on gas fired water heaters we can detect a very small trace leak of LP gas or natural gas at the side seams of the control; beware: volatiles in pipe dope or in valve label glue might also cause the TIF8800 to indicate that a leaking gas is present).
• A gas leak may be found the gas line shutoff valve.
• A gas leak may be found the appliance pilot line at the control.

You should have your plumber test/replace any suspect gas controls promptly. Replacement of a control itself should not involve significant expense. This repair should not be deferred. You should be sure that building occupants know if this or other unsafe conditions are present.

Old LP Gas Tank Leak Hazards

When inspecting old LP gas storage tanks above ground watch for corrosion, risk of rust perforation, and for leaks at control valves and fittings. Our photo below illustrates a rooftop LP gas tank installed in San Miguel de Allende, Mexico.

Check the LP gas tank's date stamp and compare it with the tank ages permitted by local building codes.

Old Indoor Natural Gas Meter Hazards

Our photo below shows an older natural gas meter that is located inside of the building. This meter was originally outdoors but building expansion enclosed it. To meet current minimum gas safety codes (in New York State) the builder was required to add a vent pipe connecting the regulator (shown at left of the gas meter) to the outdoors.

The concern is that a rupture or damage inside the natural gas regulator at the meter might otherwise leak hazardous gas into the building interior. Coincidentally the meter is adjacent to a heating furnace - we would not want leaky gas to be transported through the building ductwork - increasing the hazards involved.

Abandoned or Old Gas Piping & Shutoff Hazards

When I saw this open-ended gas valve (below left) all I could say was @#$(*u&!

All that was needed for a catastrophic fire or explosion was someone ignorant of what this valve controlled to turn it in presence of a spark or flame, or to open the valve and leave it on. This natural gas line was live and could supply a virtually infinite quantity of explosive gas in the building.

Flexible Gas Appliance Connector Installation Procedures & Warnings

The manufacturer typically warns of the following safety hazards when using flexible gas connector tubing, mostly in the form of "Do Not" admonitions that we detail

at FLEXIBLE GAS CONNECTOR INSTALL.

Excerpts are below

• Do not re-use flexible gas connectors, fittings and valves; they are designed for use only on original installations. The concern is that removal and re-use of a connector tubing and additional handling may damgae it, making it unsafe for re-use.
• Do not use flexible gas connectors with appliances that are mounted on rollers, casters, or wheels that permit the appliance to move readily about. Flexible gas connector tubing is intended for limited movement after installatin. Repeated bending, flexing, extreme vibration, stretching, can cause metal fatigue, cracks, holes and dangerous gas leaks.
• Maximum flexible gas connector tubing length is limited by code in some jurisdictions. For example in the U.S. in Massachusetts the maximum connector lenght is 36" .

What Chemicals are Used to Produce the Characteristic Odors in Natural or LP Gas?

Mercaptan gas odorant components, concentration strength, human exposure levels

Mercaptan is, according to our industry commentator J.R., a widely-recognized odorant, but only one of a number of similar-smelling products that are added to natural gas or bottled gas to assist in recognizing that a dangerous gas leak is present since natural gas alone, CH₄ (Methane) is odorless.

Photo at left: an antiquated natural gas meter in the basement of a New York home.

The product added to natural gas to provide it with a characteristic odor is a mixture of tertiary butyl mercaptan, dimethyl sulfide and n-hexane.

Commonl y in the trades the gas odorant product is just called "mercaptan".

Mercaptan is added to natural gas at a rate of 0.08cc’s/1.0 m3 of natural gas.

Therefore very little mercaptan (or other gas odorant chemicals) in the gas stream.

Gas odorants are produced by Odor-Tech, a subsidiary of Arkema, by Chevron Phillips Chemical, and others. Odor Tech also produces Mercaptan Assassin ESD - an odorant-blend kit used to clean up mercaptan spills.

Critical Hazard Limits for Natural Gas or LP Gas

According to J.R., one of our industry correspondents, odorants need to be detectible in the natural gas at 1/5 the lower explosive limit (LEL), or more properly, the lower flammable limit or LFL.

So this is the amount of natural gas required in the test.

A person is exposed to very little natural gas in the air by the time they smell it.

Mercury Hazards in Older Gas Service Regulators

This discussion got promoted to its own web page!

Please see MERCURY HAZARDS in APPLIANCES & GAS REGULATORS

LPG Propane & Natural Gas Safety Data Sheets

• Airgas, BUTANE SAFETY DATA SHEET for N-Butane Gas [PDF] (2011) Airgas USA, LLC 259 North Radnor-Chester Road Suite 100 Radnor, PA 19087-5283 1-610-687-5253 retrieved 2021/09/23 original source: https://www.airgas.com/msds/001007.pdf
• Enbridge, NATURAL GAS SAFETY DATA SHEET [PDF] (2018) Gas Service Safety Advice, retrieved 2021/09/21 originsl source: https://www.enbridgegas.com/safety - serving Ontario, Canada,
  Excerpts:
  
  Safety Data Sheets contain hazard information on the use, storage, handling and emergency procedures related to natural gas. It shows what the hazards of the product are, how to use the product safely, what to expect if the recommendations are not followed, what to do if accidents occur, how to recognize symptoms of over exposure, and what to do if such incidents occur.
  
  Natural gas is one of the safest fuels used today – but you should be aware of how to use it safely. In Ontario, Enbridge Gas safely and reliably distributes natural gas to more than 3.7 million customers, including houses, multi-family buildings, schools, hospitals, businesses and large companies.
  
  As a property owner, you're responsible for maintaining the gas line that extends past the meter into your home and for the safe operation, maintenance and repair of natural gas appliances.
• Airgas, PROPANE SAFETY DATA SHEET [PDF] (2012) Airgas USA, LLC 259 North Radnor-Chester Road Suite 100 Radnor, PA 19087-5283 1-610-687-5253

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2019-02-16 by (mod) - do older gas pressure regulators contain mercury?

Michael

This discussion got promoted to its own web page!

Please see MERCURY HAZARDS in APPLIANCES & GAS REGULATORS

On 2019-02-16 by Michael Soules

Do older gas pressure regulators leading to an individual gas appliance (gas fireplace, range, etc.) ever contain mercury? I know that older gas regulators leading into a home sometimes contain mercury, and would like to know if the pressure regulators for a single appliance can as well. (The specific situation I'm interested in involves a gas fireplace connected to a very old-looking pressure regulator.)

Here are the articles I've seen that discuss mercury pressure regulators: ... see the live link above - Mod.

Thank you for any thoughts!

On 2016-03-21 by (mod) - safety checks before turning on gas supply to new gas piping

Stephanie:

OPINION: The more components that are installed during gas line testing the more thorough and safe is your system test. There is, however, a standard for plumbing tests of gas piping for leaks that your plumbers should be able to cite and give to you.

I have found very common tiny leaks at the seam of gas regulators/valves on gas fired water heaters that no one takes as a concern.

When I have found leaks at a gas shutoff valve I've repaired or replaced the valve. Experts whose comments I've read agree with me that ignoring "small leaks" in a gas piping system (such as at shutoffs) is dangerous: who's to say the small leak today won't be an explosive leak or fire in the future?

And as you'll read in typical gas fired water heater testing instructions from a manufacturer, the manufacturer assumes the gas valves are in place:

"The appliance and its gas connection must be leak tested before placing the appliance in operation. It shall be isolated from the gas supply piping system by closing its individual manual Shut-off valve during any pressure testing of the gas supply piping system at test pressures equal to or less than 1/2 pound per square inch (3.5 kPa)."

And model codes and standards (cited below typically assume the gas valves are in place.

Watch out: "B. Before Turning Gas On. Before gas is introduced into a system of new gas piping, was the entire system inspected to determine that there are no open fittings or ends and that all valves at unused outlets are closed and plugged or capped? " - excerpt from North Dakota's NATURAL GAS SYSTEMS INSPECTION, TESTING, AND PURGING that in turn cites the standards given below.

I worry that your "cap it off and ignore the valves" plumber is making life too easy for herself.

See

• 2002 Edition National Fuel Gas Code National Fire Protection Association (NFPA 54) Section 7.1
• ASTM F2786 - 10 Standard Practice for Field Leak Testing of Polyethylene (PE) Pressure Piping Systems Using Gaseous Media Under Pressure (Pneumatic Leak Testing)
  

On 2016-03-21 by Stephanie

Plumbers have given me contradictory advice about natural gas shutoff valves within a residence, at various appliances.

One plumber tells me that we should cap off the gas line to every appliance before pressure testing, since shutoff valves are very commonly responsible for low level leaks. Another plumber directly disputes that. Can anyone give me a sanity check on this claim?

(In our case, a plumber found a leak we were smelling in a gas line to one condo, then pressure tested gas lines to other condos and said most of them were leaking, although no one was smelling leaking gas elsewhere. That plumber tells us we have a big problem with leaks in the walls,

but a second plumber says that most likely the shutoffs were leaking due to the higher pressure when testing, and we likely don't have leaks within the walls. We are trying to decide whether to start cutting holes in walls looking for leaks there, or to cap off all the lines first at the shutoffs).

On 2014-06-04 by Anonymous

my Eternal tankless water heater makes a loud noise when igniting. So loud it rattles the neighbors windows. We use propane, and the unit is configured for it. What's the cause of this?

On 2014-04-03 by Mark Christopher

When converting a 90,000BTU furnace from Natural Gas to LP Gas (Propane), what can go wrong if the contractor installs the wrong size gas orifices? For example, if the proper LP Gas orifice is supposed to be size 1.15 (.0453 dia) ..what can happen if he installed size 54 (.0550 dia)? Specifically, can it cause excessive soot and eventually plug the heat exchanger?

...

Continue reading  at CARBON MONOXIDE - CO or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• BACKDRAFTING HEATING EQUIPMENT
• ELECTRICAL WIRE CLEARANCE FROM DUCTS & PIPES
• GAS LEAK DETECTION, LP / NG
• GAS METERS - home
  • GAS METER CODES & CLEARANCE DISTANCES
  • GAS METER CODES & STANDARDS
  • GAS METER PROTECTION BOLLARDS
• GAS PIPING, VALVES, CONTROLS - home
• GAS TANKS LP / PROPANE

Suggested citation for this web page

GAS LP & NATURAL GAS SAFETY HAZARDS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to GAS APPLIANCES, PIPING, CONTROLS

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