Air Heating: Make-Up Air Units and Air Turnover Units Direct Fired Make-Up Air Units Short Lead Times. 1,000-60,000 CFM at rates of 100M-6,480M BTU with 30:1 turndown. Indirect Fired Make-Up Air Units Short Lead Times. 3,500-57,000 CFM at rates of 240M-4,500M BTU. Three or four pass heat exchanger for maximum efficiency. Air Turnover Units Short Lead Times. 4,500-100,000 CFM at rates of 240M-4,500M BTU. www.rg-inc.com