Especially contents of carbon monoxide and carbon dioxide, dioxide sulfur, nitrogen oxides and flue ashes in the air of Ulaanbaatar exceed the permitted level. The main air polluters of the city with dense industrial and traffic net are. Although the power production and consumption in Mongolia are low in comparison with the developed nations, the greenhouse gas sources are still important. The Ulaanbaatar fourth thermal power plant (TPP-4) is largest in Mongolia, which is using the modern technology and equipment It is first unit started to operate in 1983. The installed capacity of thermal power plant (TPP) is 540 MW and since 1990 it has worked with full capacity and has become the most power full plant in the country, which has 8 boilers BKZ-420-140, producing 420 tons steam with 140 atmosphere pressure per hour, and 3 turbines PT- 80-130 with 80 MW capacity and 3 turbines T-100-130 with 100 MW capacity. The TPP-4 supplies 70% electric energy to the central energy system via 110 and 220 KB electric energy transmission lines connects Ulaanbaatar, Darkhan, Erdenet and the central 8 regions. It has also produced 65% of thermal energy for Ulaanbaatar city heating. The main fuel of the TPP-4 is brown coal of the Baganuur and Shivee-Ovoo coal mines. A year usage of coal is about 2.4 million tones. Since it was put into operation, the TPP is cooperating with the Board for Environment in flue gas monitoring and keeping records. Recent years, environment and ecology pollution is becoming a critical matter. Relating to this, the TPP-4 is focusing on conformation of environment protection regulations, rules and adopting the latest technologies, which do not effect the environment negatively.