CSST and House Fires

Submitted by KimChristensen on Sat, 12/21/2013 - 09:10

CSST and house fires- CSST (corrugated stainless steel tubing) is a type of thin walled gas piping, some of which has been found to have failures culminating in house fires when lightning has struck at or near the house. It was developed in Japan in the 1980’s. Usage of CSST in the United States began in 1990 and in Lubbock in about 2000. It is present in approximately 6 million homes in the U.S. and in at least 10,000 (probably more) in Lubbock. It has a yellow plastic outer layer with corrugated stainless steel tubing inside. A newer type of CSST has a black outer layer and is designed to be more resistant to electrical damage and fire, but tests have shown that it is not completely immune to these failures either, especially in a direct lightning strike. A safer type of CSST is now available called "Flash Shield". Flash shield has a wire mesh between the black plastic outer layer and the stainless steel pipe which helps diffuse an eletrical spark, if one were to occur. CSST shouldn’t be confused with appliance flex connectors which are short in length, and used only at individual appliances (gas furnace, water heater, gas oven, etc.) to connect that appliance to the gas line. The appliance flex connectors are not having the problems that the CSST lines are having. CSST is usually run through attics, along basement ceilings or through wall cavities. 

Pros and cons- Originally, CSST was touted as a safety improvement. Because it’s flexible, it tends to hold up better in earthquakes and tornadoes, and there are fewer joints, so leakage of gas from joints is less likely. Also, it can be installed much more quickly. In areas that have earthquakes but don't have many lightning strikes, CSST may indeed be safer than the old method of piping gas- rigid black iron pipe. But in areas like Lubbock where earthquakes are rare, and lightning anything but, big problems have been occurring. Lightning strikes at or near a house can cause metallic systems in a house to become energized. Differences in voltage between the systems can cause sparks which can burn holes in CSST. Since it is carrying gas, fires have resulted. In 2012 a home in Lubbock was struck by lightning which ruptured a CSST gas line in the home, causing an explosion. The home owner and a friend were in the garage when the lightning strike occurred. The owner was injured and his friend, Brennen Teel, was killed. Lubbock Assistant Fire Marshall Lt. Elliot Eldredge was quoted as saying "What we're seeing now is that sometimes there's some issues with corrugated stainless steel tubing that gets breached during the lightning strike and then you have a natural gas-fed fire". CSST is no longer approved for new construction in Lubbock unless it's the "Flash Shield" type. What are the odds of this happening to any single house with CSST? I've never seen any odds published, but they appear to be pretty low. Of course, that's little consolation if your house ends up being one of the one's that is affected. If you think that lightning strikes are among those rare occurrences that only happen to the other guy, be sure and read the last paragraph of this blog. Every once in a while these things happen to us too.

What to do if you have CSST- For people who have CSST gas lines, replacing them with rigid iron piping is an option, but that would involve some expense (typically a few hundred up to as much as 3 or 4 thousand dollars). If  CSST lines are kept, the CSST should not be run next to any metal (air conditioning ducts, metal pipes, etc.) and it should be grounded to the house electrical ground. This may lessen the risk, but it won't completely eliminate it. The house in Lubbock where Mr. Teel was killed had gas piping that was properly grounded. Rigid iron pipe has been tested and found to hold up extremely well, even in direct lightning strikes. It appears that the risk of fire from CSST is highest in houses that have metal factory built fireplaces with a metal chimney flue and a gas log lighter down at the firebox. Chimneys stick high up into the sky and, as you know, lightning likes tall objects. Given Lubbock's general lack of very tall trees, chimneys are very attractive to lightning in this region. A strike here will easily travel down the metal flue to the gas log lighter. And just like that you've got lightning in your gas piping system (whether it's grounded where it enters the house or not). A neighbor reported that he saw lightning hit the chimney of the house where Mr. Teel died. By removing the fireplace log lighter and the gas line feeding it from the fireplace area you can avoid this scenario, and it won't cost a lot of money. Of course you'll have to find a different way to start a fire in your fireplace, but you may avoid a fire in your attic. Besides CSST and metal fireplaces, another bad mix appears to be the use of CSST in attics that have foam insulation. This is the insulation that is sprayed onto the underside of the roof decking, and it was the type in use at the house where the Lubbock man died. Foam insulation often yields an attic that is fairly airtight, (attic vents are not always installed because the entire attic is insulated from above). A CSST line in the attic was breached during the lightning strike but the resulting fire likely became starved for oxygen. Of course, the natural gas would have continued pouring into the attic through the damage hole because it's under pressure. Without any attic vents the natural gas had no way to escape. When the attic fold down stairs were opened, oxygen rushed in and created the deadly explosion.

How to tell if that lightning flash hit your house- If you have CSST gas lines and there is a lightening strike that you think may have hit your house, or very close nearby, it is highly recommended that you leave the house and turn off the gas at the gas meter (usually in the alley). Then call the Fire Department to investigate. You will have a pretty good idea if lightning has struck your house. I was in my parent's house once when it was struck by lightning. The flash of light and the thunder boom occur essentially in the same instant, (not the flash of light and then several seconds later the thunder). It's hard to describe the sound. It's not a rumble of thunder but an incredibly, incredibly loud BOOM! I almost jumped out of my skin. The damage was minimal. It knocked some nails several inches out of the drywall ceiling in the den, near the fireplace. It also knocked the metal rain cap off of the top of the chimney. Looking at it the next day, we figured it must have hit the chimney. Luckily, this was way back before CSST even existed so we didn't have a house fire to deal with. If you suspect that you have CSST in your house, have it inspected. For more information, you can visit the Brennen Teel Foundation website at www.btfgaslinesafety.org Another good source is www.csstsafety.com/‎ . Also, the Lubbock Fire Marshall's office has conducted extensive research on this subject as well as traveled to witness testing of the various systems. You can reach them at (806) 775-2646. One final note: In the Lubbock area I recommend rigid black iron pipe for gas distribution over CSST. If CSST is used, it should be the Flash Shield type. If you have non-Flash Shield CSST and decide to keep it, you should be aware of lightening and thunderstorms. --- Kim Christensen, TREC 20358

Submitted by KimChristensen on Sat, 12/21/2013 - 09:10