A fixed temperature alarm warns after the limit is crossed; a rate alarm shows unusually fast warming while the value is still in range. WHO TRS 961 Annex 9 lists high/low set-point alarms as a minimum requirement, so a rate alarm goes next to them, not in their place.
A threshold that is too sensitive sounds on every normal door opening; one that is too loose loses the early warning. Work out the ordinary rise rate of comparable trips, mark the events that needed intervention, and set the threshold in a pilot where it separates the two.
Do not switch it on until every alarm has a defined action; record the calculation window, the ordinary rate, the event rate and the outcome of the intervention.
