2 things spring to mind.
The word fireproofing is best not to be used, no substance is really fire proof, the correct term, and for your protection always say
flame retardant, you will slow down the rate of burn but never fire proof anything , not even concrete!
With upholstery you can flame retard the fabric, but the regulations also require the foam/ filling to be protected, so I would be careful of someone passing liability to you.