Air is free. I've never had to pay anyone to produce it for my respiration.
No it isn't, think of all the legislation that goes into limiting emissions and protecting vegetation in order to improve/maintain air quality. That firewood wouldn't be on public land if their weren't laws protecting the public forest from which the wood came. None of the examples you give are truly 'free' by the definition you seem to want to use: free of cost or consequence to all.