Which fuels (burning materials) can be used in a wood fired oven? I have recently made a brick wood fired oven. It's a black / dirt / Roman / traditional type of oven: where you burn the fuel (typically wood) in the same chamber where you put the food to be cooked. The normal use of this type of ovens is: 


Let the fire heat the dome and floor (bed?) of the oven up.
Once the bricks are soaked with heat (or the fire has extinguished) you take the embers (or ashes) out. 
Wait till the temperature drops down to the dish's required one, and put the food in.




As for fuel, I use wood from pallets or wood logs from prunings (which gardeners are willing to give away, mostly if you gift them loafs of bread you make with that wood).

What are the risks of using those woods for fire lit in the same place where you'll put food?

I'm quite sure there is no biological hazard with them: any virus or bacteria in the pallets, or bugs in logs will definitely be destroyed by the fire temperature (over 800C/1,500F).

What I'm concerned about is:


I don't know if my pallet's wood has been treated or not.


Is there any way to know it for a pallet found in the street?
The treatment given to pallets, would be risky if human-consumed? After being burned to ashes?

I.E.: Some pallets are given methyl bromide as fungal treatment. But its autoignition temperature is 525C/995F. Will the subproduct, after burning, still be toxic?

I can ask gardeners if they have applied insecticide or other treatment.


Some of those bug treatments are supposed to be human-safe.

But are also safe for human consumption? After been burnt to ashes?
Is there any specific treatment I should ask the gardeners?
Could the treatment be flushed away with just water?

If I bought firewood logs, can I have guarantees that they are safer / healthier / don't have treatments?

Considering they are thought to be sold for fireplaces, not for cooking.
Regarding the use of pallets, the link below is to a site that gives good examples of why not to use them for any type of repurposed project due to unknown chemical treatment, e-coli contamination, mold, fungus and other nasty things that could leach from the wood.  

We use hardwood branches from known (chemical-free) sources for smoking meat.

http://www.organicauthority.com/sanctuary/repurposed-wood-pallet-toxic.html

Here is an additional link to a pizza oven manufacturer's site with their wood recommendations.  They do not recommend using any wood that has had any sort of chemical treatment.  If you do not know the source of the wood, there is no reliable way to verify that it is chemical-free.

http://www.fornobravo.com/pizza_oven_management/choosing_wood.html