A commercial cool room holding food should keep it at or below 5°C, and most are set to run between 1°C and 4°C so there is margin for door openings and deliveries. A freezer room should keep product frozen hard, which in practice means a set point around -18°C. The catch is that the number on the controller is the air temperature at one sensor, not the temperature of the food, and the two can be several degrees apart.
Where 5°C comes from
The Food Standards Code requires potentially hazardous food to be kept at or below 5°C or at or above 60°C, unless a business can show that time outside those limits does not affect safety. Between 5°C and 60°C bacteria multiply quickly, which is why the range is called the danger zone. A cool room is set colder than 5°C not because the food needs it but because the room needs somewhere to go when the door opens.
For frozen food the standard requires it to be kept frozen; it does not name a temperature. Minus 18°C is the industry convention because it stops bacterial growth and slows the quality loss that comes with slow freezing and thawing. A freezer room that creeps up to -10°C is still frozen and still a problem, because product softens, refreezes and deteriorates.
Typical set points and when to act
| Equipment | Usual set point | Worth a call when |
|---|---|---|
| Walk-in cool room | 1°C to 4°C | Air temperature stays above 5°C an hour after the door was last shut |
| Freezer room | -18°C to -22°C | Reads warmer than -15°C, product is softening, or ice is building on the coil |
| Prep counter or under-bench fridge | 1°C to 4°C | Cannot get back below 5°C between door openings during service |
| Glass-door display cabinet | 1°C to 5°C | Front shelves are warm while the back is cold, or the doors are sweating |
| Open-front display | 2°C to 5°C | Temperature drifts with the room, or a nearby fan or vent is disturbing the air curtain |
What the controller is actually telling you
The display shows the air temperature at the sensor, which is usually positioned in the return air near the evaporator, the coldest part of the room. Food on the floor by the door, or in a tightly packed pallet in the middle, can be warmer than that reading by a useful margin. A room that shows 3°C can have product at 7°C if it has been loaded warm or the airflow is blocked.
So the reading that matters for food safety is a probe thermometer in the product, in the warmest place you can find: near the door, high on the shelving, in the middle of a dense stack. Take that reading at the start and end of the day and write it down. Two readings a day for a month tell you more about a room than any single visit can.
Normal fluctuation versus a fault
A cool room is not a laboratory. The air temperature will rise several degrees when the door is open for a delivery and should fall back within twenty to thirty minutes of it closing. Defrost cycles also cause a brief, regular rise as the evaporator warms to clear ice. Neither is a fault.
A fault looks different. The room takes longer to recover each week. The compressor runs without stopping. The reading drifts up slowly over days. Ice appears on the evaporator or the floor, or the display reads fine while the product does not. Any of those is worth a call before it becomes an urgent one.
If the room is warm right now
- Check the obvious: power, a tripped breaker, a door not fully closed, stock pushed hard against the evaporator fan.
- Take a product reading: with a probe, in the warmest place, and note the time. Check again in twenty minutes; the rate of rise tells you how long you have.
- Keep the door shut: a full, well-sealed room that stays closed will hold safe temperature for hours. An open one will not.
- Follow your food safety plan: for anything that has been above 5°C, and record what you did.
- Call with the readings: the controller value, the probe value, when it started and what changed.
A cool room that is drifting is far cheaper to fix than one that has failed, and the temperature record is what turns a vague concern into a clear diagnosis.