Protective Vents from W. L. Gore & Assoc. Inc., Newark, Del. (, handle such chores under the most-demanding circumstances, according to the manufacturer. The key is an expanded polytetraflouroethylene (ePTFE) membrane that freely passes air and gases while stopping dust and water from passing through. The vent's tough zinc-alloy housing resists corrosion and lets the vent survive in explosive environments. The vents come in a variety of sizes and configurations and can be retrofit on existing enclosures.