Tjernlund Radon Ventilation Fan RV2RV2 Ventilator For Ventilated Crawl Spaces The RV2 Radon Ventilator exhausts radon and other harmful soil gases and allows fresh outdoor air to replace them. At 220 CFM, the RV2 ventilates a 20 x 40 x 3 crawl space over 5 times per hour while using only 32 watts. Simply mount the unit against a vent opening with the included hardware and plug it in. For even greater results multiple units can be installed. Run it continuously or with a plug in timer.