A valve is provided comprising a housing, said housing containing a channel for a fluid medium, and the channel having associated therewith a sealing element which cooperates with a sealing seat. Said sealing seat is positioned in a chamber with which are associated a particle retention element in order to provide simplicity in construction and ease of installation. Said valve is designed and improved in such a manner that, once installed, it ensures optimal operation at all times while being simple in construction and easy to install.