The special felt heater can be spliced with aluminum alloy collector (OS10h/20/22/30/32/40/42) and installed on a flat roof or wall. The air goes through the black felt gap (air intake volume remains unchanged) can efficiently absorb the heat of the sun, thereby increasing the temperature of the outdoor fresh air that entering the room. As long as the felt heater is spliced, the temperature of the fresh air from outside can be increased: F7----about 10℃; F11----about 15℃; F20----about 20℃.
After a long period of outdoor dust and rain test, the air intake volume of ordinary one would be reduced by up to 3%. It can effectively filter dust and become clean after rain washing, no maintenance is required. Its service life is more than 5 years.