Vermiculite

[Midland Retty]

Dear All - your advice / help please

Have any of you come across fires involving Vermiculite granules?

The granules are to the touch like polystyrene chips (the type used to protect fragile / delicate items in parcels and packages) - springy and soft and were placed around the outside of a chimney / flue

Now I always thought vermiculite was fire resisting, but the granules don't appear to be...

Question is then is it standard practice to pour vermiculite "chips" around flues? And are they truly fire resisting in this form?

Thanks

[Midland Retty]

Nobody know anything then?

Come on you lot Im relying on you!

[Thomas Brookes]

Being honest not really up on this one but have a look at this site. I have seen the chips around old chimneys etc.

http://www.william-sinclair.co.uk/industrial/products/vermiculite

[John Webb]

According to my elderly (1979) IFE "Dictionary of Fire Technology", Vermiculiates (sounds like rodent droppings??) are "low grade micas (or hydrous silicates) which expand and exfoliate on heating to a light water-absorbant material. Used in the exfoliated form as heat and sound insulating materials...."
Then goes on to say "Used in stanchions with a hollow steel section, with or without a concrete infill and incorporating a thin outer sleeve in mild or SS filled with vermiculite/cement compound to improve fire resistance."

Doesn't sound as if Vermiculite is actually flammable, but the exfoliated chips might have absorbed dust or liquid that is?

[Midland Retty]

Thanks very much for that Thomas and John, most helpful

[Martin]

Years ago I worked in the Steel Industry Vemiculite commonly used in pit around large (1000kg plus) steel blooms at  red heat (900 C+) to provide slow/controlled cooling. Didn't ever catch fire. It did break down from flakes to a coarse powder.

Anything that could catch fire didn't usually last more than a shift in a melting shop. ( A long time ago when health risk from inhaling mica dust was ignored.)

[Midland Retty]

Intresting point Martin

I wonder why the vermiculite we encountered was smouldering.

As you all point out it should be fire resisting - perhaps as John mentioned dust and absorbtion of liquid is to blame.

[Clevelandfire]

Retty

When I worked in the steel industry we used vermiculite alot too and it is fire resisting and is found in common plasterboard. You will find that the granulated rock type you describe  is sometimes treated with an oil to make it less impregnable by water. Maybe the oil caught - causing the smouldering.