I recently purchased the Anneland hybrid full-size mattress from IKEA USA. I wanted something firm, without the sink-in feel of a full memory foam build or the bounciness of a full spring construction.
When I unwrapped it, there was a slight smell, but I followed the instructions and let it air out for 96 hours with the windows open and the central ventilation running.
Although the smell was faint at first, it intensified A LOT over those 4 days and became absolutely unbearable by day 4. It was so bad that I got a persistent headache and felt dizzy any time I entered the room. To survive staying at home over the weekend, I had to buy a pedestal fan and set it up to blow the VOCs out 24/7. I tried everything the internet recommended: vacuuming, constant airflow, you name it.
After reading up on the multiple posts and airing instructions, I gave it two weeks. In the end, I gave up, moved the mattress to the patio, and called IKEA for a refund. They said they could only refund me via an IKEA gift card, not back to my original payment method, so I asked for a replacement instead. They hauled away the first one and brought me another Anneland.
This time I left it to air out on the patio from day one with the fan blowing on it. It's been a week so far, and the exact same cycle has repeated: a faint smell for 3 days, followed by unbearable emissions from day 4 onwards. I wondered if my first mattress was defective, but after the same horrible experience with the second one, I'm convinced this is a serious quality issue. I regret spending almost $700 on a mattress I haven't been able to tolerate in the house, let alone sleep on.