Introducing the new Series 3908 Pressure & Vacuum Relief Thief Hatch – the better thief hatch from The Protectoseal Company. Precision lapping of the valve seat ensures the best possible sealing characteristics resulting in a maximum allowable leakage rate of no more than 1 SCFH at 90% of pressure / vacuum set point. The Series 3908 is designed to deliver impressive flow performance, as validated through testing established under API 2000 / ISO 28300 guidelines. Each and every thief hatch is tested and shipped with its own test certificate – quality and reliability assured!