The metabolic cart is the device that you were breathing into 
I was wondering if you knew what device it was, since not all metabolic carts are created equal.
It sounds like you were not in the ideal environment. Having no fan would certainly impact your test.
I wouldn’t think too much of the test. I offer them (in a very non-clinical setting) and unless you’re looking for insight to your physiology, you can save money by testing with a high-quality power meter, a deliberate testing protocol, and a stopwatch.
How much was your test at half-off?