How Many Un-vented Gas Appliances?

I was concerned about a 2800 square foot house that had an un-vented range, and cook-top and two un-vented gas fireplaces, plus a gas furnace with poor supply air. I was surprised to learn that the Int Gas Fuel Code Chap 6, allows for an un-vented 20 BTU/hr per cubic foot. For an un-vented stove, oven and two gas fireplaces…I figure about 103,000 BTU/hr if all were operating at the same time. But with (2800 X Eight) =22,400 cubic feet times 20 that’s 448,000 BTU/hr, so you could even throw in a couple of un-vented furnaces? No worries about water or CO or oxygen depletion?

Worry about lack of makeup air.
Recommend CO detectors near unvented fireplaces which should also follow manufacturer guidelines.
Range and kitchen have no exhaust requirements in residential.

…as described by “minimum code”.

I always recommend venting gas operated appliances, and recommend against “ventless” ones, or at least crack open a window.

Thanks, would you please clarify what “minimum code” is because I presume the rule I specified above is the overall guideline, 20 BTU/cubic/foot/per hour un-vented. Paul