I am looking to use this in a sauna, what is the fan rated for in terms of heat? 140 degrees? Also does it come with a variable speed switch? I need to tune it down to 25-30cfm

No, this product is not compatible with sauna applications or high-heat environments such as 140°F. It is not designed for that type of use. We suggest giving us a call so we can further assist you in selecting the fan that best fits your needs.