[cb_philadelphia]

Stripped back some existing, old UF wire today when I was replacing a switch and noticed some white fibrous material between the insulated copper conductors and the UF cable jacket. Any clue what it is? Looks kind of like a fiberglass substance. Should I have reason to be concerned about it?

Thanks in advance for your help!

 

[carpdad]

Not electrician. The fiber could be cushion or reinforcement against stretching. If it came out of the cable, not likely something that grew in it, just a part of the cable.

 

[AllanJ]

Take a few of the fibers. If they have some strength against stretching (tensile strength) but if you make a (180 degree) U-bend and then make the bend (bend radius) tighter and tighter until it turns into a V-bend and the fiber(s) snap in half then you almost certainly have fiberglass.

You cannot be totally unconcerned because the material could be asbestos.

Now, even fiberglass and rock wool are not totally hazard free. Tiny particles could also be inhaled so as to be hazardous.

 

[mpoulton]

If it easily pulls apart into smaller, finer strands, it's probably asbestos. If it is strong when pulled, it's more likely fiberglass.