Fire & Cellulose Insulation

What to look for when fighting fires in structures that contain cellulose insulation

By Stephen M. Coleman Jr.
Published Monday, November 28, 2011

Cellulose insulation has been around since the 1970s, although it has become more popular in recent years, as green buildings now play a larger role in our society. Cellulose insulation includes more recycled content than any other insulation material on the market. That fact aids many construction projects in earning LEED credits in the U.S. Green Building Council certification program. Leadership in Energy and Environmental Design, or LEED, is a nationally recognized green building certification system that provides third-party verification that a building or community was designed and built using strategies intended to increase energy savings. Cellulose insulation is comprised of 85 percent recycled material, including newspaper, using ammonium sulfate and borate as a fire retardant.

The borate treatment gives the cellulose insulation a very high fire safety rating in terms of combustibility. From a safety standpoint, that’s good news. As a line firefighter trying to deal with a fire in cellulose insulation, that’s not so good news. The low combustibility of the cellulose makes it easy for fires to start, but the fire retardant treatment doesn’t allow them to grow quickly, so they can continue to smolder. Dealing with a smoldering fire in cellulose insulation in attics and walls can be very challenging for firefighters, because our newer technology isn’t always reliable when investigating these fires.

Hiding Fire
When cellulose insulation burns in an attic space or within a wall, it typically burns from the bottom up, and it burns at such low temperatures that even the best thermal imaging camera (TIC) may not pick up the traces of heat. Additionally, when the insulation is blown in, it makes a thick blanket that can hide the signs of fire. So, at first glance, it can be difficult to tell that a fire is even burning. But don’t be lulled into thinking that a fire in the cellulose doesn’t exist because you don’t see it on a TIC. The tell-tale sign of a fire burning within cellulose is the smell of burning paper. The best way to be sure is to physically dig in and move the cellulose around until you get to the bottom. You may not even see smoke right away until you start digging.
 
If you do find fire burning within the cellulose, you’ll notice that it travels fairly quickly at the lowest levels of the cellulose blanket. A small fire contained to an electrical box in an attic may cause the cellulose insulation around that box to burn as far as 8 to 10 feet around the area of origin.

Important: When fighting small fires in attics or walls that have cellulose, completely remove the insulation from the house using buckets or salvage covers. This is the only true way to ensure that the burning material has been removed from the home. When removing the cellulose, once you think you’ve reached the perimeter, dig another 3 to 5 feet beyond that just to be safe.

Ceiling Strain & Confined Spaces
Caution must be taken when working a fire within a building that has cellulose insulation in an attic space. Depending on the amount of water that the insulation absorbs during fire operations,  the insulation can turn from a very light and fluffy material to a material that resembles concrete. If not installed properly, even when dry, cellulose can place a strain on the sheet rock of a ceiling. Once it becomes wet, it places a tremendous amount of strain on the ceiling, making it highly susceptible to collapse. Note: Use caution when pulling ceilings in these structures, because if/when the cellulose falls, it may come down in one large, wet, heavy sheet that may cause injury.

Fighting fires in attics and other confined spaces with cellulose insulation is a physically demanding task. Full SCBA should be worn not only because of the products of combustion, but also because cellulose insulation is extremely dusty, and chemicals such as the borates and sulfates may carry potential cancer-causing agents or carcinogens.

Points to Remember
When fighting fires in structures that contain cellulose insulation, remember the following points for a successful operation:

  • Don’t rely on TICs to tell you that a fire exists in cellulose. The only true ways to know is to smell the air and physically dig for the fire.
  • Make sure you dig all the way to the bottom of the cellulose blanket. That is where you’ll find the burning material.
  • Physically remove the burning cellulose from the building. It’s not good enough to simply extinguish the fire in it.
  • Once you get to the end of the burning cellulose, continue to search an additional 3 to 5 feet to ensure that you’ve come to the end of the smoldering cellulose.
  • Wear SCBA to reduce the health effects from the products of combustion as well as the ammonium sulfate and borate used as a fire retardant.
  • Consider ventilating the roof—it may be your only ventilation option. It is not advisable to run a PPV fan if the fire has not been contained. It makes it difficult to operate if the fan is blowing around the cellulose.
  • Ensure that you have enough personnel on scene for the operation. Removing cellulose insulation in buckets wearing full PPE and SCBA will be extremely taxing on your people.
  • If the cellulose is wet, be alert for ceiling collapse and use caution when pulling ceilings so that large, heavy sections of the cellulose don’t come down on top of you.

Cellulose is a very tricky material when it comes to firefighting. Its low combustibility is extremely beneficial to homeowners, but creates multiple challenges for firefighters. Understanding how this material works and knowing what to look for when fighting fire in a structure that contains cellulose insulation will ensure your safety as well as the continued safety of the homeowner.

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Smoldering fires in cellulose will create a very light smoke condition.The low combustibility of the cellulose makes it easy for fires to start, but the fire retardant treatment doesn’t allow them to grow quickly, so they can continue to smolder. Photo courtesy Oxford Fire Department
If firefighters are unable to locate the fire's origin in the cellulose, it allows for very deep charring of beams. Photo courtesy Oxford Fire Department
When cellulose gets wet, it has the consistency of wet concrete. Photo courtesy Oxford Fire Department
If cellulose is wet, be alert for ceiling collapse and use caution when pulling ceilings so that large, heavy sections of the cellulose don’t come down on top of you. Photo courtesy Oxford Fire Department


Fire & Cellulose Insulation

What to look for when fighting fires in structures that contain cellulose insulation smoke conditions in cellulose insulation
Smoldering fires in cellulose will create a very light smoke condition.The low combustibility of the cellulose makes it easy for fires to start, but the fire retardant treatment doesn’t allow them to grow quickly, so they can continue to smolder. Photo courtesy Oxford Fire Department

Charring of beams
If firefighters are unable to locate the fire's origin in the cellulose, it allows for very deep charring of beams. Photo courtesy Oxford Fire Department

wet cellulose
When cellulose gets wet, it has the consistency of wet concrete. Photo courtesy Oxford Fire Department

wet cellulose
If cellulose is wet, be alert for ceiling collapse and use caution when pulling ceilings so that large, heavy sections of the cellulose don’t come down on top of you. Photo courtesy Oxford Fire Department

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