OSHA has Permissible Exposure Levels for fiberglass when it is used in manufacturing plants.
Fiberglass is usually considered a large non-respirable particle. Avoid having this in your breathable air, however, most experts agree these particles are unlikely to pose a health risk.
The current guidance from EPA is not overly clear. Since fiberglass contains non-respirable particles we tend to advise levels of zero.
Please don’t use fiberglass HVAC filters.
Do use HEPA (paper) HVAC or heating system filters. The industry is now making plastic HEPA filters. We do not recommend plastic filters. The manufacturers state these filters can safety be rinsed with water. Not so. The water remains trapped in the folds of the plastic. Water encourages mold growth. Mold is in the dust in the filter. Definitely not designed for a healthy home.