The fact that fiberglass is everywhere makes it hard to pin point. The microscopic particles not only stay airborne longer than the average dust, they land on everything, intertwining and becoming part of ones clothing and carpet. And as if the microscopic glass is not enough, fiberglass emit the VOC vapor styrene (Vinyl Benzene). After your shower perhaps you put on a jacket that has not been washed in a while. You lay in bed and it comes off of your hair onto your pillow if you shower in the mornings. If your office at work is contaminated, you bring it into your car where it settles all over the interior. You bring it into your home from your clothing or purse that you had with you at work. You pick up your baby from daycare and hold him or her close to your body and the baby breathes it in. You sit on your couch before you shower. If your family attends a church or school with airborne particles, the entire family brings it into the car, and into the home. If your home itself is contaminated it is even harder as it settles on your furniture, bedding, carpets, clothing, and even the dog. Anything in the effected room or rooms. If the HVAC system is the culprit the particles will literally be everywhere. Those in the home will carry them out to places they frequent, further cross contaminating.
Houses and buildings have attics full of fiberglass, some decades old, vented to the outside. The dust blows in the wind entering open windows in neighboring homes and settles on the ground below.
Often times a person will think they are allergic to a dog, when in reality the dog has fiberglass dust sticking to the dog's coat. Or perhaps the dog is wearing a synthetic rubber collar that is emitting the styrene gas. The person bends down to pet the dog, feels a reaction and blames it on dog dander.
Carpet, be it in your home, office, church, child's daycare center or school not only acts as a sponge, holding onto the glass fibers that land on it, the carpet backing emits a VOC styrene gas. While a carpet gets vacuumed, you can never fully vacuum out all of the tiny microscopic fibers. They make their way below the surface and also intertwine with the fabric, becoming part of it. Carpet free areas can be mopped, greatly lessoning the contamination.
It is not until one starts to make a conscious effort to avoid it by cleaning up areas of the home, removing carpets and replacing the HVAC system with something like a ductless split system, does one begin to notice areas that are contaminated by spending more time in places that are not.