Unboxing a mattress in a box: expansion, smell and setup

The short answer: Carry the box to the bedroom before opening it, put the rolled mattress on its base, cut the outer plastic carefully and let it unroll. Most brands say you can sleep on it the same day, and give a day or two — sometimes three — for it to reach its full height and feel. The smell that comes out of a new foam mattress is from volatile compounds released by new foam; it usually fades over days with fresh air. If the mattress has not reached its stated height after the brand’s expansion window, measure it, photograph it and contact the brand.

Before it arrives

A boxed mattress is compact but heavy — a Queen hybrid can take two people to carry. Plan a few things first:

• Get the base ready. Assemble the frame and check the slats before delivery, so the mattress can go straight onto it.
• Clear a path from the door to the bedroom.
• Sort out the old mattress. Some retailers remove it for a fee. Otherwise, check whether your council runs hard-rubbish collections or accepts mattresses at a transfer station.
• Have scissors ready, with rounded tips if possible. Many brands include a small cutting tool.

Unboxing step by step

• Open the box in the bedroom. Once it starts expanding, a mattress is far harder to move.
• Lift the rolled mattress onto the base while it is still wrapped, with the label or arrow the right way up if there is one.
• Remove the outer plastic first, then unroll it so it lies flat on the base.
• Cut the inner plastic carefully, away from the mattress, so you never put a blade against the cover. It will start to expand as soon as air gets in.
• Remove all the plastic from under and around it.
• Leave it uncovered for a few hours if you can, with a window open, before putting on a protector and sheets.

How long it takes to expand

Most brands say a boxed mattress can be slept on within a few hours, with full height and feel taking a day or two, and up to three days for some. A few things slow it down:

• Cold. Foam is slower to recover in a cold room. In winter, warming the room helps.
• Time spent compressed. A mattress that has sat in its box for a long time can take longer to recover. Many brands advise unboxing within a set period after delivery; check the instructions.
• Thickness and construction. Thick foam mattresses tend to take longer than hybrids, where the springs help push the mattress up.

It is normal for a new mattress to feel firmer in the first days. Foam softens slightly as it is used and warmed, and your body takes time to adjust to a new surface too.

That new-mattress smell

When a foam mattress is unwrapped, it releases a smell often described as chemical or plastic. It comes from volatile organic compounds (VOCs) given off by new foam and, to a lesser degree, adhesives and packaging. It is strongest in the first hours and usually fades over days to a couple of weeks.

To speed it up:

• Unbox it in a well-ventilated room and keep windows open where you can.
• Remove all plastic promptly.
• Leave it uncovered for a few hours before putting bedding on.

Some foams are certified for low emissions — CertiPUR-US, for example, includes a limit on VOC emissions from the foam. Our guide to mattress certifications explains what those logos cover. If a strong smell persists for weeks, or causes headaches or irritation, contact the retailer.

What if it doesn’t expand properly?

Give it the full window the brand states. Then:

• Measure the height at the centre and at a corner, and compare it with the height on the product page.
• Look for soft spots, dips or uneven areas that have not filled out.
• Photograph it, with a tape measure in the shot.
• Contact the brand or retailer with your order number and the photos.

A mattress that does not reach its advertised specification is not of acceptable quality, and Australian Consumer Law gives you a remedy for that, separately from any sleep trial. Our guide to buying online or in store explains those rights.

Can I sleep on it the first night?

In most cases, yes. Most brands say a boxed mattress is usable within a few hours of opening, even if it has not quite reached full height. If the instructions say to wait longer, follow them.

The box and packaging

The cardboard box can go in household recycling once flattened. Rules for soft plastics vary by area, so check with your council. Keep the order details and any law tag or label, which you may need for a warranty claim. You will not be able to re-roll the mattress into its box; if you return it during a trial, the brand usually arranges collection as it is.

Common questions

How long does a mattress in a box take to expand?
Most brands say it is usable within a few hours and fully expanded within one to three days. A cold room slows it down.

Is the smell from a new mattress harmful?
It comes from VOCs released by new foam and usually fades over days with ventilation. If it persists or causes symptoms, contact the retailer and air the room well.

Can I leave a mattress in its box for a while before opening it?
Only for as long as the brand allows. Leaving a mattress compressed for too long can stop it expanding fully.

Is a boxed mattress lower quality than one delivered flat?
No. Compression is a way of shipping it, not a grade of mattress. Many hybrids and all-foam mattresses are designed to be compressed. See the best mattresses in a box.