Global Commercial Boiler Market, By Fuel (Natural Gas, Oil, Coal, Others), Capacity (≥ 0.3 - ≤ 2.5 MMBtu/hr, > 2.5 - ≤ 10 MMBtu/hr, > 10 - ≤ 50 MMBtu/hr, > 50 - ≤ 100 MMBtu/hr, > 100 - ≤ 250 MMBtu/hr), Technology (Condensing, Non-Condensing), Product