Is this asbestos insulation?
Looks like fiberglass or rockwool(this is not asbestos). Safest to have it tested but you should seal off the space and not enter it until you know. I've two Aunts who died from indirect contact with asbestos.

Even if it is fiberglass you should be wearing a filter mask as it is essentially spun silica (glass) and the particles can cause silicosis (and skin irritation).