Smoke

Ronald Harvey <rsharvey [at] tidewater__net> writes

>I have just received a call about smoke and fire related odors in an
>historic house.  I am interesting in knowing conservators
>experiences with treating smoke and soot deposits within an historic
>house--original plaster walls, reproduction wallpaper, multiple
>paint layers on interior woodwork.

The past year I've had four fire-damage projects--one gallery and
three homes.  Steve Prins and I have learned a few things from
industry about removing smoke volatiles from objects and structures.
He may have some additional comments and I'll forward the question
to him.  Barry Bauman, at the Chicago Conservation Center is known
by  the post-fire recovery industry as somewhat of a clearinghouse
for smoke and fire damaged paintings and objects. The ServiceMaster
company, in particular, told me that Barry has used ozone very
effectively.  He may have some suggestions as well and it may be
worth a call.  Here's a summary of my experiences:

    1.  The smoke smell compounds are volatile and come out whatever
        material they have attached themselves to in curve very much
        liken to half-life curves of heat and chemical distribution
        models.  They come out fastest when the concentration in the
        surrounding air is lowest and concentration in the wall,
        object, floor, whatever is highest.  The rate of evolution
        slows when the concentration in the surrounding air becomes
        increasingly saturated and as the concentration in the
        substrate decreases. Really just the opposite of the
        application curve when the smoke compounds were distributed
        onto the surfaces during the fire.

    2.  Getting rate that you can get the compounds out of surfaces
        is increased by:

        *   Keeping the concentration in the surrounding air low,
            e.g. Using zeolites or activated charcoal, as you
            suggest, (useful only in enclosed containers for
            objects) or air washing with fresh-air continuously;

        *   Raising the temperature of the object that holds the
            smoke compounds and the surrounding air (the rate of
            release is temperature dependent). Heating the room to
            about 90 degrees F with fresh forced air has been very
            effective is speeding up the rate of smoke diffusion and
            release.  This also works well with the objects in
            closed containers containing zeolites and activated
            charcoal.  Obviously, the ability of the object and
            materials in question to safely withstand elevated
            temperatures and lowered RH is an important controlling
            factor, as well.  Remember, though, the smoke was
            deposited at several hundred times that temperature and,
            while the good news is that it will eventually release
            to a point below human sensitivity, there just is no
            fast, cheap or easy way to speed it up.

    3.  The compounds can be oxidized into smaller, non-smoky
        materials using ozone, which is what the fire-clean-up
        industry does. They use ozone generators and chambers or
        sealed rooms.  For non-porous surfaces, this can be pretty
        effective.   In porous surfaces, it tends to break up the
        first layer of deposition and then result in delayed release
        of more deeply deposited smoke compounds.  It also causes
        accelerated oxidation of the substrate material--as you can
        imagine, bad for paper, textiles, anything with high surface
        area to mass ratios and oxidation sensitive materials (most
        everything!).

    4.  For surfaces that can be wet-treated, initiating the
        oxidation with hydrogen peroxide solutions and UV light,
        either from sun-light or from tanning lamps, works extremely
        well.

                                  ***
                  Conservation DistList Instance 12:76
                  Distributed: Friday, March 26, 1999
                       Message Id: cdl-12-76-001
                                  ***