This article is particularly about cold rooms and walk-in freezers for storage of medicines and vaccines. We are explaining on deciding the number of sensors and location of sensors of a temperature monitoring and alert system. The operator or owner of the cold room has to continuously monitor and record the temperature. Sometimes it may be essential to record humidity also. The question is where to place the sensors in the cold room continuous monitoring system. These are the sensors which generate alarms in case the temperature or humidity goes above the permitted limits.
First of all, we have to carry out a temperature mapping study to decide the hot and cold points. Based on these, we can decide the number and location of sensors. We can see that in many cold rooms, the operator places sensors of a monitoring system without a mapping study. The sensor will be located at his most convenient location. Sometimes this may be close to the door, which is irrational. If an auditor asks a question as to how the location was decided, there won’t be any answer.
We will explain how to decide the same.
After conducting a mapping study, we can identify the hot and cold points of the cold room. As an example, we will consider a small sized cold room. We assume that we use 10 data loggers to conduct the mapping study. After analyzing the complete data of a loaded test, we can find out the hottest and the coldest points. We should not consider data of the empty test, door opening test and power failure test for this purpose. The air circulation and stabilization of the cold room will be tested in a loaded test.
The hottest point and coldest point will be normally in different places. We have to place one temperature sensor at the hottest point and one sensor at the coldest point. Please see the following examples for further clarification. In both the examples we are assuming cold storage of 2 to 8°C for storage of medicines. It is assumed that we used 10 data loggers for the mapping study. DL1 is data logger1, DL2 is data logger 2 and so on.
In this example we will consider the following maximum and minimum values of the data loggers:
In this case, you can see that location of DL 6 is the cold point. Similarly, the location of DL8 is the hottest point. These are the weakest points in the cold room. Now you have to place one data logger at the location of DL6 and one data logger at the location of DL8.
In this example we will consider the following maximum and minimum values of the data loggers:
In this case, you can see that locations of DL 6 & DL3 are the cold points. There are two cold points. However, there is only one hot point which is DL8. These are the weakest points in the cold room. In this case, you have to place one data logger each at the locations of DL3, DL6 and DL8.
For humidity, there are no hot and cold points. Generally, the humidity quickly equalizes across the entire cold room, once we close the room. Hence, you can consider the following general rules:
We should not place the Temperature & humidity data logger near to the door. The humidity near the door increases as soon as the door is opened.
However, if humidity is a very critical parameter for your stored goods, you may have to consider more humidity data loggers for the continuous monitoring system.
In principle, the methodology is the same as above. You should take data of temperature mapping study during a loaded test excluding data of power failure test, door opening test etc. You have to decide at least one each of hot point and cold point and place sensors accordingly.
The main limitation is that you can place a sensor only on the wall. So even if you find a hot point somewhere in the middle of the van, you cannot place a sensor there. This is because inside a van you always have a different pattern of loading. Hence you can install the sensor for continuous monitoring somewhere on the nearby wall or ceiling.
The logic for selection of the sensors point is to closely monitor the variations. You should receive an alert as soon as the temperature goes above or below the limits. You have to select the location and number of sensors accordingly. In case the cooing unit is not working, the hottest point will be the first one to cross the upper limit. Hence you will receive an alert as soon as the hottest point crosses the limit. Same is the case for the cold spot.
We provide all kind of temperature mapping study, temperature qualification study, temperature monitoring systems and temperature alert systems across the world.
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Requirement of sensors for Temperature and Humidity
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During routine temperaturing monitoring in hot point.How we place the temperature sensor?
1. Temperature sensor will touch with wall or it should be in air. Please send reference guideline also.
Hot points are identified in a temperature mapping study. Due to practical limitations, it might be sometimes difficult to place a sensor at the exact hot points. Examples of limitations are areas with the movement of the forklift, middle of a walkway etc. In such cases, the sensor is ideally placed in the nearest possible location.
Dear Vacker team
As per your above article it is mentioned that Hot spot cold spot monitoring is applicable to cold rooms, warehouse, Reefers or van.
What about small lab freezers and refrigerators where we keep small bottles. Since the area is very small is it relevant to identify the hotspot cold spot in these and is it necessary to monitor these points? any reference/guidelines can be provided on this ?
Your response is highly appreciated