An emissions cleaning module includes a flow conduit having an upstream end fluidly connected to a source of exhaust fluid and a downstream end fluidly connected to a mixer module. An injector module has an outlet orientated to inject injection fluid into the flow conduit upstream the mixer module. A low pressure cavity downstream the injector module outlet is fluidly connected to the flow conduit or the mixer module by an open mouth orientated such that a flow of exhaust fluid along the flow conduit flows over the open mouth creating a pressure reduction within the low pressure cavity.