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Modern tent vinyl and flame retardancy

October 1st, 2019 / By: / Safety

Do you know how your tent fabric performed on a flammability test—and can you explain the results to your fire marshal?

One of the most tragic days in tent history occurred 75 years ago: The Hartford circus fire. 

Some 7,000 spectators were enjoying a circus performance on July 6, 1944, in Hartford, Conn., when a fire spread rapidly through the tent. About 167 people died (the exact number is unknown) from burns, asphyxiation, trampling and other causes, and more than 700 people were injured. The cause of the fire was never determined, but investigators focused on the possibility of a carelessly tossed cigarette. 

The contributing factors to the disaster would horrify tent professionals today. According to a 2014 article from the Hartford Courant:

“The tent had been waterproofed with a mixture of paraffin wax and gasoline. The circus had dozens of fire extinguishers, but most weren’t located in the tent—they were near generators—and some were inoperable. There were no “No Smoking” signs. There were far too few exits, and some were blocked by animal runways. There was no Hartford fire engine on site. Few of the hoses on the circus water trucks fit city hydrants.”

As often happens in the wake of man-made disasters, the fire spurred local officials to develop new regulations for temporary shows that were the toughest in the nation at that time, according to the Courant.

Flame retardancy today

Today’s fire codes and tent fabrics would likely prevent such a catastrophe. But misinformation about fire retardancy and tent fabrics still exists, even among those who are charged with regulating tented events.

Jeff Sparks, sales director for fabric manufacturer Herculite Products Inc., Emigsville, Pa., says that some fire marshals misunderstand modern tent vinyl, which is inherently fire retardant and does not require retreatment. 

“They will associate the PVC fabrics of the tent industry with camping tents or nylons that have treatments,” he says. “We get this all the time, where the fire marshal comes back and says the tent fabric needs to be retreated. Some fire marshals are really up to date on their knowledge of various fabric, but some are not, and there is still a lot of disconnect out there.”  

Another issue for the industry, Sparks says, is the various tests and standards for flammability. There is no federal regulatory body for fire retardancy; however, the National Fire Protection Association (NFPA) developed NFPA 701 Test Method 2, a voluntary industry specification for tent vinyl and other outdoor fabric products. This is the flammability specification quoted in the International Fire Code. However, the NFPA does not do the testing and certification of the fabric. Rather, tests are performed by independent labs that are qualified to conduct the test.

Tents and fabric structures used in California must meet the specifications of California State Fire Marshal (CSFM) Title 19. Unlike the NFPA, the CSFM tests materials and issues certificates and annual renewals. And because the state of California tends to be a front-runner on regulatory issues, a CSFM certification is sometimes accepted in other localities. Herculite also subjects its fabric to another standard, ASTM 6413, which is required for government and military contracts. 

Test results

While details differ, all of the tests involve igniting flame to a fabric sample and then removing the flame, Sparks says. The test results in an afterburn number (the time it took for the sample fabric to stop burning) and a char length number (how far the fabric burned). 

“If you take the flame away, the fire on the sample should go out in four seconds or less,” Sparks says. “And it shouldn’t burn more than seven inches. Some tests would require less than that, but if it’s in that range, it’s a flame-retardant tent fabric.”

If a fire marshal requests more information about flammability for a permit, the tent renter usually goes back to the tent manufacturer, and if the manufacturer’s data doesn’t satisfy the marshal, the tent manufacturer will go back to the fabric supplier, Sparks says. Herculite conducts tests on every 500 yards of fabric. 

“We will send a fire marshal all the tests—‘Here are 2,000 tests over the last few years, here are the averages, here’s the mean.’ That typically satisfies the fire marshal most of the time,” he says.

When purchasing new tent fabric, tent renters should know what is required by the jurisdictions where the tent will be installed and which certification was obtained for the tent vinyl being purchased. Sparks recommends asking for the data that resulted from the test in addition to a certificate, especially when working with a new supplier.

“It’s important not to just get a piece of paper that says ‘cert’ but to get a test result, actually see some form of test results, either by an independent lab or by the manufacturer’s lab,” he says. “Rental companies should understand what the test method is, what it means, and have some data to back it up from the manufacturer of the fabric.” 


Sidebar: The Hartford circus fire

The Hartford circus fire is remembered as one the worst fire disasters in U.S. history. In addition to raw footage posted on YouTube and other websites, the story of the fire has been told in several nonfiction books, as well as at least one novel and a legal book that reviews the settlement between the victims and the circus. History buffs may enjoy: 

The Circus Fire: A True Story of an American Tragedy by Steward O’Nan

The Hartford Circus Fire: Tragedy Under the Big Top by Michael Skidgell

A Matter of Degree: The Hartford Circus Fire and the Mystery of Little Miss 1565 by Dan Massey and Rick Davey

Masters of Illusions: A Novel of the Connecticut Circus Fire by Mary-Ann Tirone Smith

The Great Hartford Circus Fire: Creative Settlement of Mass Disasters by Henry S. Cohn and David Bollier