Waste treatment produces smells and gases that cannot be allowed outside. That's why the ECOP4RC of the Barcelona metropolitan area enclosed premises are at a lower pressure than the outside. In this way, when a door is opened no air gets out of the plant.

This depressurization is achieved by means of a complex circuit of extractors that send the air from the premises to odor control systems. In addition, the belts that smell stronger and emit a higher amount of particles, such as the ones that transport organic matter, are covered and have their own means of extraction.

The odor control system includes acid and alkaline scrubbers, followed by bio-filters.