Air Filters and Indoor Pesticides

I have been working in an office adjacent to our woodworking shop for eight years and can say for sure that not a single time the HVAC air ducts have been cleaned nor filters replaced. The room was shared by five persons, had no daylight and everyone was sick with respiratory infections year round more than ever before joining that company. I and some others had blood shot eyes each night and hair loss. All of this improved within a month after I changed companies.
Does anyone know how often air return filters and ducts should be replaced/ cleaned? And another question: to what degree are pesticides allowed indoors? (We had a fumigator go through once every couple of years to spray out the whole building on a weekend - I guess only to keep a few "silverfishies" at bay. The guy looked like a walking corpse himself - and he actually passed away two years ago.) I am just wondering if there are any safety standards in North America for air quality in office zones.

[caregiver222]

There are such standards and in your situation they have obviously been violated. That being said, go on with your life. The exterminators without exception (in my experience) disregard U.S. federal law and common sense in the application of pesticides. Since you are no longer working at this establishment you might feel inclined to make a written complaint to OSHA on behalf of the other employees.

[Trialanderror]

Thank you and sorry for my late reply....
I will definitely intervene faster if I see similar methods of operations at the new work place. The former establishment evaporated in bankrupcy by now. Thanks for your reassurance!