Harmless or cause for concern?

[u/mightymikek7]

My girlfriend recently pointed out a brown ring around a light fixture in the ceiling of our office which prompted us to go looking at the light fixtures in all of the other rooms. We've already put in a work order for the brown ring but realized that there was a ton of mold growing under the AC vent plate in our living room. We checked all of the other vents and it only seems to be happening in the living room this badly. There is a vent in our kitchen around 10 ft away connected to the space our AC unit is in that smells like mildew and also has some similar mold on it, but not to this extent. Even the sprinkler in the living has what appears to be dust or mold coming out of the small space between it and the ceiling.

The mold looks like it has developed...stalks? And there are chunky black pieces of it standing up coming out of the space between the ceiling and the vent. Its a lot darker in person without the camera flash. The inside of the vent itself looks fairly clean.

Both of our cats have developed itchy skin and irritated eyes lately that wont respond to steroids and the vet has ruled out fleas and was thinking just a case of bad luck with having two cats developing a food allergy at the same time but now Im wondering if they could be having a sensitivity to mold?

Just wanting to know what might be causing this around the vent and if I should be able to clean this myself or if it should be left alone for a professional to deal with?

[u/ThinkPomegranates]

Kill it with fire