The roaches are not in your cupboard, they are in the fridge's engine: the bay-first fix

Kitchens chasing roaches scrub cupboards and bait shelves for weeks while the colony sleeps twenty feet away from the food, in the one warm, oily, undisturbed compartment in the house: the machine room behind your fridge. The compressor bay is to a Lagos kitchen what a gutter pit is to a compound - the harbourage every spray misses because it is never the surface that was treated. Fix the bay and the cupboard problems stop appearing; treat the cupboard and the bay repopulates it by Thursday.

The two sentences of entomology this fix needs

Cockroaches want four things: warmth, food, water and a tight edge to press their bodies against - and the fridge's rear bay serves all four: the compressor's steady heat, motor-oil film and dust on the fins, crumbs and spills under the unit, and a thousand ideal seams. The second fact is why they ride the broadcast: German roaches in particular move along the warmth and the wall voids the fridge shares with the sockets and cabinets, which is why the animals you switch on light in one kitchen at midnight came - and go - through the appliance's own compartments. The bay is the hub; every other sighting is a branch.

The sequence, in order, because order is the treatment

1. Pull and unplug: the job starts at the socket, not the spray - the whole fix happens on a pulled appliance. Roll it out, check the rear for the tell-tale (speckled droppings, egg cases the size of a kidney bean, the oily smell that is their congregation, not the motor's).
2. Vacuum first, deep: the creviced bay, the drip tray, the base pan under the compressor - suction takes the population, the eggs and the droppings that mark the trail; dispose of the bag outside, immediately, or you have relocated the colony into the bin and the bin into the kitchen.
3. Brush the condenser while you are there: the dust coat on the fins is both their carpet and the reason the fridge runs hot and hungry - one dry brush ends two bills (this desk's cooling-coils guide covers the energy half).
4. Gel bait, not fog: pea-sized dots in every corner of the bay's structure, behind the kick strip and where the line runs - bait is the colony's own courier service, the poisoned return that reaches the eggs' hatchlings; sprays kill what they touch and scatter the rest into the wall voids you just failed to treat.
5. A thin dust line where they walk: food-grade diatomaceous earth or borax in a barely-visible veil behind the unit and along the baseboard - the pile is the failure mode: an inch of fluff, and they walk around it like a hedge. This is the whole technique: a road dust looks like and cannot cross.
6. Seal and starve: the gap between the floor and the wall's skirt, the pipe collars at the back, the open cupboard void beside the motor - a little expanding foam or cement after the bait has finished its week. No cardboard boxes on or behind the fridge: glue and corrugation are the species' favourite apartment; everything stored there moves into lidded plastic.

The safety boundaries, both ends

Against the machine: aerosol anywhere near a running motor is how a kitchen gets a second incident - solvent mist plus electrical sparks is a fire the can's own warning prints for the same reason this page quotes it, and a wet-washed bay short-cuts the appliance that shelters it. Against the food: roaches cross from the bay into the cabinet through the shared seams - after the treatment week, the interior gets its honest audit (all open packs into jars, gaskets wiped, shelves washed), because the bay fix protects the kitchen only if the kitchen was not the second nest. And the household-level truth: in a block of flats, your gel cannot win a building's war - widespread or neighbouring sightings make it a landlord-and-professional conversation, and this desk draws the line there without embarrassment.

The verdict, as a rule

Pull it out, vacuum the bay, bait the structure, dust the roads, seal the doors, and bin the cardboard - once, properly, in that order, beats every spray you have already bought. The fridge's engine room will be warm again tomorrow; make sure only one species finds that comfortable.