Suitable corrugated filter grids are mounted on the suction intakes and are positioned with a downward inclination towards the conveyor of the machine, their lower ends allowing drops to fall on to this conveyor. 5 to about 5 percent by weight of an alkanolamine; about 0. The thermostat may also include a temperature sensor and a microprocessor programmed to detect occupancy based on measurements from the passive infrared sensor.