Neal is right, I'd guess that, since there is no intake pipe and the door to that area is louvered, that the area around the furnace meets the manufacturer's requirements for adequate combustion air without an exterior air source. However, it's been my experience that a lot of the time these furnace guys don't take into account things like gas clothes dryers and gas water heaters that are operating in close proximity to these devices and which impact combustion air requirements. That looks like the manual for the furnace on the right side; did you pull it out, open it up and read the combustion air requirements? Also, sometimes they'll have louvered doors opening into a little room that, when the door to that room is closed, provides far far less combustion air than is required. You've got to look at the whole picture. If there are other gas appliances in close proximity, I generally estimate the volume of the adjacent space, total up the BTU/HR requirement for all appliances, divide that by a thousand, and then multiply it by 50 to see if the it meets the basic rule-of-thumb combustion air requirement for gas appliances. If not, and I can't confirm with the manual that the existing space is adequate despite being less than that required by the rule of thumb, I write it up to be checked out by an HVAC pro. ONE TEAM - ONE FIGHT!!! Mike