Product Description Industrial Scientific Ventis PRO SERIES 4 & 5 O2 Oxygen Sensor, Measuring Range: 0-30% of vol. in 0.1% increments. 4 series sensors can be installed in locations 1 or 2 of the Ventis Pro. (This sensor will not fit or work with Ventis MX4 Series Gas Monitors)Has your O2 sensor failed or has a measuring range that's all over the place? It might be time to replace it. Repair your Industrial Scientific Ventis Pro Multi-Gas monitor by purchasing a new genuine Industrial Scientific (O2) Oxygen Sensor.Need some DIY help changing a sensor or just some friendly technical help with repairing your instrument? Call customer service at 1-800-949-7233.