Dirty AC

So coming home from labor day from camping it was ninety plus degrees outdoors. As we opened the front door of the house it was also close to ninety inside. Who would think to leave the air-conditioner on all weekend while we were gone? As soon as my husband turned on the air-conditioner he started sneezing from the dust that he should have cleaned out to filter first before turning it on. It had been at least a month since the AC was on and it must have been some mold that hit him straight in the face as he turned it on. He shut it off but its too late for him he did pull the filter and clean it afterwards.