On ETC submittals drawings there is a line that states:
Dimmer rack generates approximately 4% of connected load as heat output. Dimmer Room must have climate control. Maintain between 32 degrees Fahrenheit (0 degrees Centigrade) to 104 degrees Fahrenheit (40 degrees Centigrade), humidity between 30% and 95% non-condensing, and an altitude below 6500 feet (2000 meters).
As the air is less dense at higher altitudes, it can become more difficult to properly cool high-density dimming systems. Dimming systems such as Unison dimmer racks or Sensor dimmer racks, installed in high-altitude environments and used under full load conditions should be maintained with a proper HVAC cooling budget dictated by dimmer efficiency and BTU output. As long as proper cooling is maintained, there will be no issues. In addition, the dimmers are self-monitoring and will safely turn off if not enough cooling is available at any time.
In the specific case of the Sensor CEM module, the normal setting for the airflow sensor was not efficient enough for high altitude installations and called for re-calibration on site by a service technician. The CEM+ control module has been designed with a new more efficient air flow sensor and no longer requires the re-calibration. Cem3 uses different methods to determine air flow so this will not be a concern. If your installation will include classic Sensor racks with CEM modules, it may be necessary to send the controller in for repair to have it re-calibrated.