A large reverberation room of approximately 280 m3 (10,000 ft3) used in the air conditioning, heating and refrigeration industry, was evaluated and found to be in need of improvements to meet the requirements of recent updates to the American Heating and Refrigeration Institute (AHRI) Standard 220. Additionally, it was desired to extend the measurement capabilities of the room down to the 63 Hz octave band. Toward this, we were engaged to conduct qualification tests of the reverberation room to establish its performance relative to the more recent version of the standard, and to determine if its qualification could be extended down to the frequency bands of 50, 63, and 80Hz. The initial qualification test results showed that the room did not qualify for the extended low frequencies and had some irregularities in the 100 Hz band. This paper reports on the process and work done to extend the room qualification down to the low frequency bands and correct irregularities in the 100 Hz band.