An injector configured to be placed in a process chamber of a batch furnace assembly for injecting a gas into said process chamber. The injector has an elongated, tubular housing enclosing an injection chamber. The housing has a gas inlet opening for supplying a gas from a gas source to the injection chamber, at least one gas supply opening for supplying the gas from the injection chamber into the process chamber, and a circumferential wall extending in a longitudinal direction of the housing. The circumferential wall comprises a first lateral wall half and a second lateral wall half. Both lateral wall halves substantially span a length of the housing in the longitudinal direction. The first and second lateral wall halves are fastened to each other by means of mechanical fastening.