What flame retardants are used on FSK-faced insulation batts?

We are planning to install formaldehyde-free fiberglass insulation batts with 1 1/2 " insulation baffles in an attic that will have ridge and soffit vents. Need FSK [foil-scrim-kraft] faced so that it can be left exposed. Worried about flame retardants, as they build up in the body and do not flush out (store in our fat tissue).

Any idea how to find out what flame retardants are added to FSK facing? Is each product different?