Pink fiberglass insulation good for duct insulation?

I've got some leftover Owens Corning pink insulation R12 left. Brand news, not used stuff from a demolition job.
Wondering is this would be acceptable as duct insulation. I've got a 60 foot long side-split house with the furnance at one end. The duct that carries all the forced air to the upstairs is an 8' x 16' duct that then splits into all the rooms upstairs. Iit bascially runs 50'. I think I can easily insulated about 30 ' of that run.
With wood siding on the second story any little bit will help me I think both with a/c and heat.
Is this stuff fire safe? The duct work heats up to about 100 F or more on a long furnace cycle and cools to about 58 or 56 F on a long a/c cycle.
I'm in Canada so you bascially have forced airheat/cooling on 11 months a years in some way.
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It's fibreglass, for heavens sake. If you are worried about heating damage, half the USA and Canada would be in trouble. Same with cold. If they use it on the outside of a house, I hope your inside the house desn't get below 0F.
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