Make up a high humidity shed box. A warm towel in a plastic shoe box works well. Make sure the towel is good an soaked, you can even add some warm water to the box. Let it soak for 30 minutes, then use a paper towel to see if retained she(if there is one) will come off the vent area. It looks like there might be a retained shed in that area. The warm water will also loosen up any crusties so you can wipe them away and clean the vent up.