In the 1970s and 1980s, millions of wooden buildings, both new and old, were built with preservatives that were later found to be neurotoxic and carcinogenic. Now, a special process can neutralize these chemicals in existing buildings, saving them from demolition.
Two preservatives, lindane and pentachlorophenol (PCP), are used to prevent fungi and wood-eating insects. Although both chemicals are now widely banned, wood that has been treated with them continues to emit toxic fumes, posing a health risk to people in affected buildings.
Possible solutions to the problem include covering the wood with insulation or taking it apart and disposing of it as toxic waste. Both methods can be expensive and time-consuming, and can also ruin the aesthetics of a heritage building with exposed wooden features.
Looking for a simpler alternative, scientists at Germany's Fraunhofer Institute for Building Physics developed a process called CycloPlasma.
In the first step of the technique, a gel containing a nontoxic chemical called cyclodextrin is brushed onto the wood like varnish. While the gel does not affect the structure or appearance of the wood, it penetrates into the pores of the wood, adsorbing and binding lindane and PCP.
Chief scientist Dr. Andrea Burdack-Freitag explained: "Cyclodextrin is a ring-shaped chain of glucose molecules obtained from enzymatic hydrolysis of starch. The ring structure of the sugar chain surrounds lindane and pentachlorophenol in a cavity, thus completely encapsulating them."
Burdack-Freitag told us that if the preservative is simply applied to the surface of the wood initially, once the gel has absorbed the preservative, it can be washed off and safely disposed of. If the preservative is pressure impregnated deep into the wood, the gel dries out and remains in place, encapsulating the chemicals permanently.
That said, if the wood contains a lot of preservatives, the gel may become saturated with it. Therefore, in order to neutralize the excess lindane and PCP fumes that cannot be adsorbed, a "plasma device" needs to be hung from the ceiling of the room. Electrodes in the housing generate a plasma gas through which a gas stream containing contaminants passes. Plasma gas chemically degrades lindane and pentachlorophenol. Additionally, activated carbon filters prevent gaseous degradation products from escaping the device.
The CycloPlasma technology is currently being field-tested in a historic mill loft at the Freilichtmuseum Glentleiten in Germany.