What is a latex mattress sprayed with to make it fire retardant?

I have many allergies to chemicals and really want to buy a mattress made from natural fibres like your Artisan Natural. I have previously had bad headaches from off gassing from a memory foam mattress. Are natural mattresses sprayed with fire resistant chemicals or are they just natural?

I have seen a wool mattress that claims to be chemical free but was wondering about others. >