In particular a porous substrate (FS) like a fabric. Process to clean a substrate, comprising a step of subjecting the substrate to an air-water spray (SPR), generated using a spraying means (N) comprising an air passage (OPA) and a water passage (OPW), wherein air is greater than 90% by volume of the spray, the air velocity is greater than 80 m/s and wherein said air passage does not coaxially surround said water passage. Device to clean soiled fabric (FS) comprising a feed water container (CW) and an air compressor (AC) in fluid communication with a spray nozzle (N) comprising an air passage and a water passage, said device being capable of generating an air pressure in the range of 1 to 3 bar (absolute) and an air velocity greater than 80 m/s at the exit of said nozzle; and the air is greater than 90% volume of said spray, and wherein said air passage does not coaxially surround said water passage. An external mix spray nozzle is especially preferred in the device.