Sponge blocks, also known as foam blocks, were frequently used as insulation material under the roofs of residential and commercial buildings during the first three-quarters of the 20th Century. They were also employed wherever heat or flame posed a hazard, and thus were found installed around furnaces, boilers and steam pipes. Not surprisingly, asbestos was one of the primary ingredients of such materials.
According to a website maintained by the University of Wisconsin’s maintenance department, asbestos block insulation was installed as late as the mid-1970s, and used to support steam pipes in locations where they hung from joists underneath the floor above. The website also notes that the material from which these blocks are made is “high-percentage asbestos,” and is likely to become friable if disturbed in any way.
“Friability” is defined as the ability to crush a given material into dust capable of floating in the air with the use of hand pressure alone. Friable asbestos fibers can float in the air for days, but cannot be seen with the unaided eye.
If you have reason to believe that sponge blocks are installed in your home, you have a number of options. Most sources recommend that if such asbestos-containing materials are not in a friable state then they should simply be left alone. However, according to Michael Bowker, writing in Fatal Deception: The Terrifying True Story of How Asbestos is Killing America, it is highly inadvisable to simply ignore the problem. Asbestos sponge-blocks will ultimately deteriorate over time, placing your health and that of your family at risk.
One option is to seal the material with some type of resin. This is probably the most cost-effective method. The other is to either (A) have it removed professionally, or (B) do the job yourself.
The second option is highly inadvisable. Although homeowners are legally entitled to do their own asbestos abatement on buildings that serve as their primary residence, the work involves extensive preparation. In addition, strict regulations kick in when the asbestos waste is removed from the premises. It must be placed in plastic bags no less than 6 mils thick, sealed with duct tape, clearly labeled, and disposed of only at authorized toxic waste sites. In the state of Colorado, even the vehicle used to transport the waste must carry clearly-visible warning signs.
If the property is used for rental or is some type of business into which the general public is allowed, you have no choice but to use licensed asbestos contractors or face legal penalties.