Because wood is such a porous material it can be infused by the gaseous by products of a fire. The higher temperature in the room and higher pressure literally drives the vapors into the honeycomb we call wood. After the fire the wood continues to "degas" by the principle of diffusion whereby hydrocarbons want to migrate from where there are many (in the frame) to where there are few (the atmosphere). A basic tenet of High School chemistry.
This however is a slow process. Some of the gaseous by products from a fire smell bad a relatively low molecular densities.
One way to speed the process up is to wrap the frame in a cotton cloth to protect it. Buy some 5 or 10 mil polyethylene sheeting and heat seal it or glue the edges, save for one, which will be the opening. In the center of the bag cut a hole and get a sheet of metal or plastic to make a 4 x 4" flange. To this glue a connector to attach to your vacuum source (vacuum cleaner or better Gast, Rotron pump). Place the cloth wrapped article in the patented bag. Seal the opening by folding it several times and clamping it with two wood or metal bars. A slight leak is not a problem.
Pull a vacuum on the bag, with a vacuum cleaner you cannot use it continuously, this is what a vane pump such as the Gast is ideal, it has a longer duty cycle. Creating a vacuum speeds up the degassing of the organics that are embedded in the wood. The time varies depending on the density and thickness of the article. A small amount of heat could also help but be careful not to melt the plastic.
At the Smithsonian they use critically controlled vacuum ovens to dry and degas documents and other artifacts.
Its possible if one had the skills of one Wile E Coyote to build such an oven out of a 55 gallon drum.
The problem with ozone is that it is a highly reactive and corrosive gas. It can oxidize most metals and burn many organic substances (linseed oil, acrylics and painted frames). This is of course with a protracted exposure of several hours and it will indeed oxidize the fires byproducts. Ozone as I said is not selective it does not know which are the desireable organics and the undesirable ones. It gets them all.
You can buy ozone generators from pet stores and if used carefully for a brief time can speed up the process. Sort of like a wash and rinse cycle in the laundry. Ozone and then vacuum.
My 2 denari
Dan Serra