Walk the natural pest aisle and it's all sprays: under 1% peppermint oil, atomised onto a surface, evaporated within hours. You spray, you feel productive, you spray again Thursday.
- Peppermint does the heavy lifting — a rodent's olfactory sensitivity dwarfs ours.
- Cinnamon adds a second persistent aromatic so the scent load doesn't collapse.
- Cedarwood brings the profile used in closets and grain storage for a century.
- Castor oil is the one that matters — the carrier that slows evaporation from hours into months.
That's what buys you 30 to 90 days per pouch — and where you put it decides which end of the range you get. Still, enclosed air buys the full 90: under a sink, a closed cabinet, a sealed bin, a parked vehicle. Moving air cuts it to 30 or 45: garages, attics, barns, engine bays.
How to check: get close and smell it. Faded to almost nothing means spent. Look every 30 days and you'll never run a dead barrier without knowing.