A passive shipper is a piece of engineering with an expiry clock, not a box with ice in it. Build it wrong and it fails silently: the logger reads fine for the first ten hours and the product freezes in hour twelve.
Three decisions that matter
Insulation class
Expanded polystyrene for routes under twenty-four hours, vacuum insulated panel above that. VIP costs more per unit and pays for itself the first time a long route hits an unplanned delay.
Phase-change medium
Water ice sits at 0 °C, which is below the bottom of a 2 – 8 °C band. Product packed directly against it freezes. We use phase-change packs formulated to hold at the band, conditioned to their transition point, and separated from product by a qualified insert.
Conditioning time
Packs must be fully through their phase transition before packing, which takes a full overnight cycle in a dedicated room. Half-conditioned packs are the single most common cause of a shipper that fails at hour eight of a twenty-four hour profile.
- Qualified profiles for 24, 48, 72 and 96 hour routes, mapped in summer and winter conditions.
- Build sheets signed off per consignment, with pack lot numbers recorded.
- Conditioning room temperature logged and reviewed daily.
