Will it smell when unpacked, and how does it break in?

Very little smell. The CertiPUR-US certified foams are independently tested for low VOCs, and because this mattress ships flat-packed rather than tightly rolled, any new-foam scent is faint from the start and clears in under 12 hours with a window open. It is fiberglass-free and built in Ontario. As a firm bed, expect it to feel stiff the first week, then settle into its support as your body adjusts over the first few weeks.