Maxitrol 12A04 and 12A06 vent limiting devices (1/8" NPT) for RV48, RV52, RV53, RV61, R400S, R500S and R600S regulators. According to Maxitrol, they remove the need to pipe the vent outdoors on these regulators. Installation by a qualified technician, per CSA B149.1. See gas pressure regulators.