Trying to Find the Right Valve

My husband called me the other day while I was at home taking care of the kids, and he told me that he needed me to do something for him.  I asked him what it was, and he said that he needed me to get on the web, and look up “industrial control vacuum relief valves“, and let him know if there was a place that was selling them in town.  I told him that I didn’t really know what to look for, but he told me to do it anyways.  After I searched for a bit, I told him that he should just check out the hardware store.