Possible fungal issues in greenhouse?

So the property I acquired has a greenhouse, the plastic variety. It had no ventilation or thermal mass, needless to say, it's fairly useless. I'm in the process of adding thermal mass and vents, but the air in there hurts my lungs. I have done a google search, but everything I've found is in regards to plant damage not molds and mildews that like 140F+ degrees, and how they can be damaging to people. I'm hoping that the ventilation will improve the situation, because leaving the doors open for a while does seem to make the air better, not great, but better. Is there something else I should be doing?

On a side note, the plant that survives those conditions is the yellow star thistle.

I've seen greenhouses equipped with box fans in their end walls distributing humidity via water dripping over a filter of some kind...and this was in Florida. But yes! What actions would they take to preserve air quality?

I hazard to guess that the water droplets distributed by the fans are of the consistency of public swimming pool water (yuck!) and that this preventive measure keeps fungal colonies in check.

A fundamental aspect of the Universe might be revealed in
the allegory of bleach being more cost effective than vinegar.