The short version
- Keep relative humidity below 60%, ideally 45 to 55%
- Measure humidity inside the stock area, not just the building
- Keep temperatures stable to avoid condensation
- Use dehumidifiers and keep air moving
- Store off the floor and 100 to 150mm clear of external walls
- Do not seal stock in plastic unless it is fully dry
- Use desiccants in boxes and cartons
- Rotate stock first in, first out
- Inspect samples of every inbound delivery
- Treat a musty smell as an early warning
Control humidity
Relative humidity is the single most important factor. Keep it below 60%, and ideally between 45 and 55%. Measure it where the stock actually sits, using a hygrometer or data logger inside the stock area, because a warehouse can vary a great deal from one end to the other and from floor to top racking.
Keep temperatures stable
Large swings in temperature cause condensation, especially near doors, roofs and external walls. Stable temperatures matter more than warm ones. Avoid storing stock where it is exposed to direct sun through roof lights or where heating cycles on and off sharply.
Dehumidify and keep air moving
In damp buildings or damp months, dehumidifiers make a real difference. Air circulation matters too: still air allows moisture to settle in pockets between cartons. Leave gaps between stacks and make sure air can move around the racking.
Store stock off the floor and away from walls
Floors and external walls are where moisture gathers. Keep stock on pallets or racking, off the floor, and 100 to 150mm clear of external walls.
Be careful with plastic
Plastic wrap and sealed bags trap moisture. Only seal stock in plastic if it is completely dry, and never wrap stock that has come in cold and damp from a container before it has had time to acclimatise.
Use desiccants and rotate stock
Desiccant sachets in boxes and cartons absorb moisture and help protect goods in storage. Rotate stock on a first in, first out basis, so nothing sits untouched in a corner for months.
Check what comes in
Inspect a sample of every inbound delivery on arrival, and check containers at devanning. Open a few boxes, look at the tissue, the linings and the insoles, and smell them. A musty or mouldy odour is often the earliest warning sign, and it is worth acting on even when nothing is visible yet.
If you find mould
Isolate the affected units from sound stock straight away, photograph what you find, and avoid repacking it into clean cartons until it has been treated. Then get specialist advice before deciding whether to write it off.
A simple routine to keep on top of it
- Daily:
- glance at the humidity reading in each stock area
- Weekly:
- check dehumidifiers are running and emptied
- On every delivery:
- open a sample of boxes and smell them
- Monthly:
- walk the racking, looking at floor level and external walls
- Seasonally:
- review readings, as damp months need more attention
Stock that has been remediated
Remediated stock should go into dry, well ventilated storage and be sold through in normal rotation. The same conditions that stop mould on new stock apply here, and they matter just as much.