My workplace has a terrible stench on the first floor of our building. The first couple of times we've experienced the smell we were positive it was a dead rat that had gotten into the heating/air vents. We had different companies perform duct cleaning and put in deodorizing gel blocks into the air units and it helped. The next time the problem occurred we had a pest control company come out to kill rats that were running thru vents or walls and they sprayed Sporicidin into the air as well as the heating/air units. This seemed to work but only for a while. Now the smell is back. I think it has to do with our air conditioning units. We found that the units were low on refrigerant and that there were frozen on the inside and out. Our rooftop unit had a panel loose and it was frozen inside too. The contractors fixed that problem and today I come in to work and it stinks badly. I'm confused because it's the same smell we had when we thought it was a dead rat but I know we had that problem with the ice forming in the air conditioning units. I think it might be the stagnant water in the vents. What could it be?

We had the pest control people come out again and checks for new ways of pests getting in and recheck the work they had done previously and they say everything looks good and they are sure what it is.

Has anyone ever experienced this before? How did you handle it? Thank you!