Inside older ceramic fuse holders often is a piece of woven asbestos. This was for insulation and to stop arcing. They often fall out when fuses are replaced and can often be found lying at the bottom of electrical cabinets.

Woven segments of asbestos inside two different size fuse holders.
Close-up of woven fuse lining
A pile of discarded fuses and asbestos fuse linings.

Get our book Electricians Guide to Asbestos for more on the asbestos hazards faced by Electricians