The languid calm of a summer afternoon was shattered on July 28, 1997, when an explosion leveled Keltie’s Bum Steer, a popular restaurant on Route 121 in Brewster, NY.
The blast was of such force that windows were blown out of cars in the parking lot in the adjacent Fox Ridge Motor Inn were ripped off their frames. Killed in the explosion was the restaurant’s 41-year-old manager, Robert Sterman, and 25-year- old Ronika Ferrusi of Carmel, who was at Keltie’s to interview for a waitress job. Five others suffered serious burns and other injuries. Officials have ruled the explosion an accident. As much as 20 pounds of propane — equal to a barbecue grill tank — leaked into the space beneath Keltie’s Bum Steer.
Key Facts About Propane
▪ Propane (liquid petroleum gas) has no odor, taste or color in its natural state. A distinctive odorant — ethyl mercaptan — is added to propane.
▪ Propane is heavier than air, flowing like water and collecting in low areas, such as a basement or cellar.
▪ Propane can lose its odor on a variety of circumstances. Mercaptan reacts with rust inside tanks and lines, and can be stripped from the gas by soil if a buried line leaks. Mercaptan can also be adsorbed by concrete, masonary, drywall and other porous building materials. Tests show that propane can be deodorized very rapidly.
▪ Propane has 25 times more energy than natural gas. Propane incidents tend to be explosive, with extensive structural damage and multiple fatalities.
▪ Propane should never be stored indoors. Any residence or business supplied with propane should have a propane detector.
Before the restaurant opened to the public, as the staff prepared for the evening meal, a spark from a malfunctioning vacuum cleaner ignited the propane gas, causing the lethal detonation.
The Keltie’s Bum Steer explosion is a type of incident that occurs with alarming frequency. According to the National Fire Incident Reporting System, there are about 2,500 propane fires and explosions annually in the US, killing about 20 people and injuring about 330 others.
In many of these cases, survivors report that they never smelled gas.
The propane industry has known for at least 40 years that propane can lose its odor under a variety of circumstances.
“Everybody admits that odor fade exists, but the question is how much it occurs and how significant it is,” said Ron Medford of the Consumer Product Safety Commission (CPSC), who led a task force studying the problem.
Propane, or LP gas, has no odor in its natural state. A strong-smelling substance called ethyl mercaptan is added to propane to warn consumers of a leak.
Experts say that the odor of propane can fade as it is stored in tanks. Ethyl mercaptan reacts with rust and metal surfaces inside steel tanks, causing the odorant to leech out of the gas.
Research done in the laboratories of the Arthur D. Little Co. for the CPSC found that the odor can significantly fade within five to seven days after a propane tank is filled.
Timothy Dunn, a chemical engineer in Atlanta who has investigated more than 300 propane fires, said that in nearly one-quarter of the cases the propane was found to have no mercaptan “in any significant amount.” Dunn conducted experiments showing “considerable depletion of odorant in as little as three weeks” after a tank is filled, he said.
When the odor of propane fades, the culprit tanks are usually either brand-new or old tanks that have not been in continuous use. Experts believe that after exposure to mercaptan for months or years, a steel tank will become seasoned and no longer promote the loss of odor.
If an empty propane tank is allowed to remain open to the air, a new layer of rust can form on the inside. When it is filled with propane, the problem of odor fade starts all over again.
“It’s true that if you leave [propane] tanks open to the air, you can get condensation of moisture and contaminants into the bottle, and that can be a problem,” said CPSC spokesman Ken Giles.
But the problem of odor fade is not limited to older, rusty tanks that have been left open to the air. Odor fade has also been observed in new tanks as well.
Esso Petroleum Canada conducted tests of new one-pound propane cylinders, the type used for camping stoves and hand-held torches. The cylinders were tested about six months after being filled by the manufacturer. In six of nine cylinders, no measurable ethyl mercaptan remained in the propane.
“Any fading that occurs does occur very quickly,” said Ian Campbell, the Esso scientist who ran the tests.
The mercaptan odor of propane can also be absorbed by soil and porous building materials. Tests done for the CPSC by three different independent laboratories found that mercaptan can be absorbed by mortar, concrete, drywall and other materials.
Arthur D. Little Co. did an experiment in which a concrete block was placed in a chamber, simulating the dimensions of a typical American basement, which was then filled with propane. Six hours later, no mercaptan could be detected in the gas.
Absorption by mortar and soil are particular concerns because propane acts much differently than natural gas when released into the air. Natural gas is lighter than air and tends to dissipate if leaked.
Propane, however, is heavier than air and tends to collect in low-lying places such as basements and cellars where soil, concrete and drywall are often found. Keltie’s Bum Steer, for example, was built over a swimming pool used as a foundation. According to fire officials, this was the area into which the propane leaked.
Absorption by soil is also a concern because large propane tanks are often buried underground at homes where the fuel is used for heating and cooking. “In the event of a leak, soil can strip the odorant out of the propane,” said Dunn.
Although propane odor fade has been studied for years by the U.S. Consumer Product Safety Commission (CPSC) and industry groups, little information about the hazard is provided to consumers. Propane-fueled appliances and tanks are required to have labels warning consumers what do if they smell leaking gas, but do not inform consumers that they may not smell the gas.
“These guys in the industry have known about [odor fade] problems since the 1950s,” said Kansas City attorney James Wirkin. “They are making so much money by selling propane, why on God’s green earth would they want to tell anybody about the problems of ethyl mercaptan?”
Industry officials say they are taking steps to address the hazards of propane. “The odor fade problem is being addressed very aggressively,” said Bruce Sweicicki, vice president of technical services of the National Propane Gas Association.
“We have pretty much identified with a good deal of certainty that odor fade can be attributed to the walls of some containers which forms various ferric oxides — rust and some other things — that react with the odorant in the propane,” he said.,/p>
Sweicicki disputes research showing that mercaptan is absorbed by concrete, soil and porous materials.,/p>
NLPA takes a low-key approach to the issue of odor fade. The association printed a pamphlet that mentions odor fade, but critics charge that the association does not do enough to bring the problem to the attention of consumers.
A consumer information web site sponsored by NLPA (http://www.propanegas.com) does not include any information about odor fade. The web site does, however, claim that propane has “an enviable safety record” and is “the safest way to provide heat” to the home.
Other experts suggest that the safety record of propane is less than exemplary. “Accidents with [propane] gas are dramatically out of proportion” for the number of people who use the fuel, said chemical engineer Alan Bullerdiek of Buffalo, NY. “They represent ten times the number of accidents as natural gas.”
Bullerdiek was contracted by the CPSC to do an analysis of residential propane use that discovered serious problems with odor fade in tanks and absorption by soil and masonry. “Ethyl mercaptan is unreasonably dangerous and defective in the absence of a vapor detector,” he said.
Originally appeared in Danbury (CT) News-Times, 7/27/98, p.A1.
Contact me for further information about propane odor fade.