I have a large ST 504 boiler I'm in the process of tidying. Inside the side plates there's a 1/8" sheet of light-grey/off-white heat insulation. Is this likely to contain anything I shouldn't be giving house room to? The stuff looks like original fitting and the boiler appears not very old and to have done little work, although the heat insulation is fraying along the bottom edges.
Are there any modern 1/8" sheet replacements I could use, or am I fretting unnecessarily. The only stuff the local CH boiler factors could come up with was about 3/8" thick.