Real-time temperature and humidity monitoring: what to measure

Measuring temperature is easy. The hard part is deciding which threshold to use, how long to tolerate a deviation, and who to wake up at three in the morning.

The variables that actually matter

In cold chain and laboratories, five variables cover nearly everything:

• Temperature: the main one. For vaccines and blood products the typical range is 2 to 8 degrees.
• Relative humidity: decides whether the packaging and the product hold up. Critical in warehouses and ripening rooms.
• Door opening: the number one cause of real deviations, and the easiest to overlook.
• CO₂: in ripening chambers, greenhouses and enclosed spaces with staff.
• Pressure: relevant in clean rooms and in process lines.

Door opening deserves its own note: without it, a temperature deviation looks like equipment failure when in fact someone left the cold room open for twenty minutes. It is the cheapest variable to measure and the one that explains the most.

Setting a threshold without creating noise

A threshold is not one number, it is three: the valid range, the warning margin and the minimum duration. A real example from a vaccine cold room: range 2 to 8 degrees, warning within half a degree of the limit, and a critical alert only if the deviation holds for two consecutive readings.

That last part is what saves the project. Without a minimum duration, every normal door opening raises an alert, and a team that receives false alerts learns to ignore all of them.

How often to measure

For cold chain, every one to five minutes is enough and keeps the history manageable. Measuring every second does not warn you earlier: the thermal inertia of a cold room is minutes, not seconds. What does matter is that there are no gaps.

The record is the product

The alert saves today’s batch. The record saves this year’s audit. Store every reading with local time and an explicit zone, mark gaps as gaps, and keep the history exportable without depending on us.

Today Edgemon measures temperature and humidity with its own sensors, sends email and SMS alerts with an activation delay so a door opened for a moment does not trigger one, and keeps an audit-ready history. If you want to see it against your own monitoring points, get in touch.