I have an A/C that emits a very foul odor after being on for a few hours.
>It has an easy to clean removable filter which I clean very frequently.
A/C odors usually occur when the unit is first turned on: not after a few hours. The odor is usually caused by algae growing on the coils. The coils need be kept clean, of course; but beyond that, there are slow-dissolving tablets which maintain an algaecide level in the drip pan. In a pinch, you can use an ounce of the blue Lysol.
I'm puzzled by the fact that this odor occurs, not initially, but after the A/C has being running for hours. This makes me think that the odor is not from the usual source, algae, but from something mechanical or electrical: something that's getting hot.
Sears' theory about the cooking odors being redistributed sounds like nonsense to me. As odor molecules in the air pass over the A/C coils they become entrained in the condensate and drip into the drip pan.
I do not suspect your pets as being a part of the problem. Sorry I couldn't be more helpful.
Michael