I recently suffered a fire in my workshop and am now quite familiar
with smoke damage.  I will try to summarize what I know here in a very
simplistic fashion, without any complex chemistry terms.

I did a fair amount of on-line research in order to determine the best
course of action with respect to salvaging or replacing specific items.
I ended up salvaging many expensive and delicate items but did not
understand the working of the insurance companies so I basically got
screwed financially.

My fire was very limited in what actually burned but the smoke damage
was extreme.  This was largely due to the fact that some plastic
machine parts had burned.  If you have suffered an insured loss, you
might also want to check out my blog entry which mentions some of the
things I learned about dealing with insurance companies.

  http://spencersviews.blogspot.com/ 

The fire in my shop was a smoldering fire and produced a lot of smoke.
Basically, a fire will turn whatever it burns into a mixture of ash,
carbon dioxide (CO2), carbon monoxide (CO), water vapor and a 'really
nice' mixture of other gases and suspended particles.  Depending on the
material that burns and the available oxygen supply, the results can
vary widely.  Complete combustion will produce just CO2, water and ash.
This is not what happens in a house fire.

Several factors influence whether damage will be caused to any item in
the fire area.  I will limit this brief discussion to smoke damage.
The gas vapor suspended particle mess is smoke.  It is the products of
incomplete combustion that will cause damage if they get to places in
the item of concern where they will cause damage.

For a variety of reasons, one item can suffer damage while another
might not.  Some things that influence this are proximity to the fire,
convection patterns during the fire, relative temperatures of the
effected items with respect to the air temperature, and the thermal
mass of the items or components within them.

Smoke can definitely contain acid producing chemicals that, when
precipitated on metal, will cause severe damage over time.  Whether
or not these chemicals are precipitated depends on all the conditions
mentioned above.  In the case of my fire, which occurred in an unheated
building in the winter with snow on the ground, the conditions were
just right for severe damage to any item of high thermal mass.

The high thermal mass insured that damp air laden with moist chemicals
would condense on these surfaces.  Cast iron machine tools were
dripping with rust after the fire, whereas other items were barely
effected -- just covered with a little toxic slime on the surface.

Due to convection patterns, some surfaces were heavily coated with
sludge while other areas escaped largely unaffected.  I took apart
every piece of electronic equipment that could not be replaced easily
and used solvents and ultrasonic cleaners to clean circuit boards,
dried them carefully and reassembled them.  So far, everything is still
working that I cleaned.  With replaceable items, it is generally
considered that these items are beyond repair.  I only bothered with
items that were very expensive and which the insurance company offered
a very low depreciated value.

A piano could definitely suffer damage to all the action pins and other
metal parts if moist acidic air entered the case and condensed on these
items.  For condensation to occur, the moist air must enter the piano
and the metal parts need to be at the "dew point" and must remain as
such for a long enough time to deposit enough of an acidic residue to
cause damage.  The only way to know is to remove some sample parts and
to examine them with a microscope or if you have a really big budget,
have the parts chemically analyzed.  If the strings are showing more
rust than there was before the fire, it is very likely that some acidic
chemicals have been deposited on them.

Probably the most relevant consideration is actually the smell that
may be difficult to remove from the piano.  Surfaces can be wiped clean
with special cleaning cloths and sponges.  I forget the name of the
sponge but it is the crepe rubber sponge used for cleaning lamp shades,
etc.  Solvents can cause more trouble by driving the smelly components
farther into porous materials.

The smell may be less of a problem in a church or in a large room with
a lot of people, but even a small smoky item in a small room will
really stink the place up, especially on a warm day.  To know how the
piano will smell on a warm or damp day, tent it, turn the heat and
humidity up and see how it smells in the tent.

I used just 20 feet of Romex wire that was in my shop fire stored in
the attic, in my house.  I cleaned it with simple green and still
noticed a smell emanating from the wall in the house, months later.

Ozone works wonders at removing smoke odor but it will also damage
rubber and plastic items.  You can build a simple ozone generator
yourself if you don't want to spend a fortune renting one.  I plan to
run mine in my workshop this summer after assessing the smoke smell
when I return.

I did not have all the sheetrock and insulation removed and replaced
because I thought I could live with a little smoke smell.  I did not
want to suffer with the remodeling which I thought was not necessary.
After getting screwed by the insurance company with respect to
depreciation, etc., my approach would be different now -- I would have
had the interior completely stripped and re-insulated.

Best regards, Spencer Chase
Garberville, California
http://www.spencerserolls.com/