The mattress is the dampest thing in your bedroom: the dry-out routine

A sleeping human hands the mattress a litre or two of water vapour a week - the reason a mattress in a closed Lagos bedroom smells faintly sweet by the rains even in a clean house, and the reason the routine below is the least glamorous, most effective hygiene in the home. The mattress is not dirty because you are; it is damp because physics is, and the fix is air.

The quarterly four

• Strip and stand: on a bright dry morning, take off the sheets and - the step everyone skips - stand the mattress on its end against the wall, bare side out. A mattress lying flat dries its top and drinks its bottom; vertical, both faces see air at once. An hour in a cross-draft room does more than any spray.
• Sun, in courses: a true hour of direct sun on the fabric is the old remedy with real evidence behind it - UV at the surface and heat in the fibres do the deodorising no product matches. But the modern foams resent long baking: two short sessions a year, memory foam in the shade-and-air version of the same day. The sun also fades and dries the cover, and a faded cover cracks - the goal is dry, not brown.
• Rotate - and flip if it allows: the body's weight carves a valley where it sleeps, and the valley holds the damp; a quarter-turn each season (and a top-to-bottom flip on double-sided models, which most newer foam singles are not - read the label's own diagram) keeps the surface even and the drying faces alternating. The valley that already exists is a signal to raise the frequency, not to buy a topper over it.
• Vacuum the seams, then the frame: the piping seam is where skin dust collects and where the first grey line of surface mould declares itself; the vacuum's crease tool along every edge takes thirty seconds, and the frame - the slats or the board the mattress sits on - gets the same pass underneath, because the frame's damp is the mattress's damp, one layer down.

What the smell under the bed means

The must that hits you when you strip a mattress that has been on a solid base for months is the base's fault as much as the mattress's: a sealed platform blocks the underside's only air route, and the result is the cold condensation the concrete article warns about, at sleeping height. The two fixes the furniture makers will not advertise: slatted bases with real gaps, and - when the bed frame is what it is - the standing-airing routine above becomes the whole maintenance, not an extra. A dark spot that stays after drying, with a fuzzy edge and a smell that returns within days of cleaning, is established mould - and at that point the honest advice is the mould article's: a mattress is porous, deep growth in foam is not a surface job, and the safe decision on a heavily affected mattress is replacement and the frame's clean-up together, not a spray and a hope.

The three habits that end most of the four

A protector with breathability on the label (the cheap vinyl type that "keeps the mattress new" keeps the water in the mattress, which is the opposite of new), the bed-making discipline of leaving it open for an hour after waking - the sheets folded back while the bathroom happens is free and it works - and no bed under a window's condensation line with the curtain pooling at the frame. The bedroom dries the house that dries you; the mattress is simply the thing closest to the proof.