Natural gas has no smell of its own. The smell everyone knows, the one people describe as rotten eggs, is put into the gas on purpose, so that a leak announces itself long before it can explode. When a house or a building blows up, the first question is not what sparked it. It is whether the warning worked, and it is one word.
Odorant. Natural gas is “colorless, odorless, and tasteless,” and gas companies add a sulfur compound called mercaptan so people can find a leak (EIA). Federal pipeline safety law requires it. Gas in a distribution line “must contain a natural odorant or be odorized so that at a concentration in air of one-fifth of the lower explosive limit, the gas is readily detectable by a person with a normal sense of smell” (49 CFR 192.625). The numbers behind that sentence are the point. Methane, the main part of natural gas, burns in air only inside a narrow band, from about 5 percent of the air to about 16; below it the mixture is too lean to ignite, above it too rich. Researchers at the federal occupational-safety institute measured the limits at 5.0 and 15.7 percent. One-fifth of the lower limit is about 1 percent. The rule wants the warning to arrive at a fifth of the danger. The company also has to check that the warning is there: an operator must periodically sample its gas with an instrument that measures the concentration at which the odor becomes readily detectable. In Texas, the Railroad Commission’s rules require the gas pipelines and distribution systems inside the state to follow those federal standards (16 Texas Administrative Code Section 8.1).
When the warning fails. The smell can fade. Houston’s gas utility tells its own customers that odorant can be lost through “adsorption, absorption and oxidation,” and that new pipe, rust, moisture, soil conditions around an underground leak, and little or no flow over a long stretch can all reduce it. Its advice is blunt: “DO NOT rely on your sense of smell alone” (CenterPoint Energy). The rule is written for a person with a normal sense of smell, and not every person has one. So when a leak goes unnoticed, the questions are concrete. Was the gas odorized? Did the company’s own readings show it? Had anyone reported the smell before?
Who owns which pipe. The duty does not stop with the utility, and it does not all belong to it. A gas company that does not maintain a customer’s buried piping past the meter has to tell the customer so in writing: that it does not maintain that piping, that buried piping left unmaintained “may be subject to the potential hazards of corrosion and leakage,” and that it should be periodically inspected for leaks (49 CFR 192.16). Past that line, the questions move to the owner of the property, which is premises liability; to the plumber or contractor who installed or repaired the line or the appliance; and to the maker of an appliance, valve or connector that failed, which is a product liability case. Texas divides responsibility among all of them (Civil Practice and Remedies Code Section 33.003), which is the arithmetic of Comparative Fault. A rule as specific as the odorant rule is at least the measure of what a careful operator does; whether breaking it is negligence as a matter of law is the question Negligence Per Se walks through.
What it does to a body. A gas explosion injures in layers: burns to the skin and to the airway, which is what Fire describes; blast injury to the lungs and the ears, which is what Fertilizer explains; and the crush of a building that comes down on the people inside.
The evidence. The meter, the regulator, the service line, the house piping, the appliance and its connector are physical evidence. The company’s odorant readings and its leak records are paper evidence. Both should be preserved before anything is repaired, replaced or hauled away, which is what Spoliation is about.
If you smell gas. The federal pipeline safety agency puts it in order: leave the area on foot immediately and do not try to find the leak; do not use a telephone or cell phone, or anything else that could make a spark; then “call 911 from a safe location” and notify the gas company (PHMSA). The Railroad Commission’s public-education sheet adds: do not turn on any lights or appliances, and use a neighbor’s phone (Railroad Commission of Texas).
The smell is the warning the law requires. When a building explodes, the case is about who was supposed to keep that warning working, and who owned the pipe that failed.
The law: 49 CFR 192.625 (odorization of gas); 49 CFR 192.16 (customer notification); 16 Tex. Admin. Code § 8.1 (Texas applies the federal pipeline safety standards); Tex. Civ. Prac. & Rem. Code § 33.003. The science: U.S. Energy Information Administration, Natural gas explained (colorless, odorless, and tasteless; mercaptan added; mostly methane); Cashdollar, Zlochower, Green, Thomas and Hertzberg, Flammability of Methane, Propane, and Hydrogen Gases (NIOSH, 1998) (methane: 5.0 and 15.7 percent). The warnings: CenterPoint Energy, Information on Natural Gas Odorant; PHMSA, Pipeline Leak Recognition and What to Do; Railroad Commission of Texas, Gas Leaks (public-education sample). General information, not legal advice.
