clearnroom temperature monitoring

August 3, 2022

Temperature and Humidity Monitor for Cleanroom: Is It Accurate?

Did you know that the size of the cleanroom technology global market was valued at $4 billion in 2020? Additionally, this market is expected to undergo an expansion at a CAGR (compound annual growth rate) of 5.4% between 2021 and 2028.

If you’re in the cleanroom industry and you have a cleanroom, you might feel stressed. Specifically, you might feel stressed about ensuring that the humidity and temperature are correct in your cleanroom.

Fortunately, in this article, we’ll review how you can ensure that your humidity and temperature monitor is accurate. Finally, you can have a humidity and temperature monitoring system that works. Read on to learn more.

Environmental Requirements for Cleanrooms

When you’re using a cleanroom, there are a variety of requirements the cleanroom needs to meet. These specifications will vary depending on the type of work you’re doing in the cleanroom. For example, if you have air ionizers, you need very low humidity levels.

This is so you can prevent problems with an electrical discharge.

All cleanrooms have environmental-control specifications. These specifications will define the lower and upper limits of two different things.

One of these is the temperature of the room. The other is the relative humidity or RH. Additional things that will have to be controlled include contamination, flow, and pressure. 

Why Monitoring Humidity and Temperature Matters

Within a cleanroom, temperature and humidity monitoring are essential for the reduction of the build-up of control static. They are also essential for the reduction of microbial growth. Additionally, they ensure employee comfort.

There are several factors that RH influences. These factors could end up degrading the cleanroom’s performance. These factors include:

  • The build-up of static charge
  • Bacteria growth
  • Moisture condensation
  • Metal corrosion
  • Photolithographic degradation

Additionally, these factors include water absorption and personnel comfort. Also, humidity has an impact on particle control. When it’s too high, humidity can be the reason why staff members in the cleanroom sweat.

In conditions of low humidity, something else can occur. In this situation, static electricity can end up affecting particles’ movement.

For example, if the environment of the cleanroom is too dry, residual particles that are on supply packaging or labels might stick to gloves (or other surfaces). Humidity that’s lower than 30% can cause problems for employees.

This can lead to respiratory discomfort and cracked skin. On the other hand, a relative humidity that’s between 40% and 60% minimizes bacterial impact. It also falls within a zone of personal comfort.

How to Ensure the Accuracy of the Measurement of Humidity

Even though a relative humidity monitor plays a role in a cleanroom that isn’t incredibly great, its failure can cause serious problems. For this reason, it’s important to consider certain factors that impact the functioning of sensors.

Installation Location

Relative humidity depends on temperature. This affects the installation and placement of relative humidity sensors. Using an example can help to illustrate the problem that can occur if installation and placement aren’t ideal.

Say that only 40 mm of the 190-mm stainless steel probe of an instrument are exposed to the cleanroom’s process air.

In this case, the other probe part might function as a heat source or sink—depending on the environment in which it is. This goes to show that, even if a humidity-sensing element is carefully designed, there can be a problem.

It could end up causing there to be a relative humidity measurement error. This error would depend on the difference between the temperature of the process-air and the environment that surrounds the probe’s exposed portion.

Within a laboratory environment, it’s easy to measure this error. Fortunately, there are ways you can avoid this problem from occurring.

Installing Devices Away From Certain Equipment Types

If there’s equipment in your cleanroom that generates heat, you should ensure that you install the devices that measure humidity away from these pieces of equipment. This is even though a cleanroom’s good airflow will usually minimize convective-heat problems.

The reason you should do this despite that is that hot or warm equipment radiates heat. As a result, it can potentially create a discrepancy in temperature. So, it can create a corresponding error in measurement.

A loop-powered device that has an output of 2-40-mA can dissipate some of its power as heat. This dissipation could have an effect on RH instruments that are wall-mounted.

Choosing the Right Type of RH Devices

Some wall-mounted relative humidity devices that are housed in enclosures will heat themselves. When they do this, they do so by several degrees. As a result, they experience measurement errors that are significant.

RH devices that have short probes can prevent this from occurring. This is the case when these probes isolate, from the electronics of the instruments, the element that senses humidity.

Location Based on Moisture Protection Efforts

It’s also important to protect your RH device’s humidity sensors from moisture. If there are any cooling coils in your cleanroom that create entrained water droplets, you should keep the humidity sensors far enough away from the coils. This way, they won’t be affected by these droplets.

If there are any ultrasonic-humidification or steam-injection elements, you should also keep the humidity sensors away from them.

Even though a large number of relative humidity probes have filters that protect, from water, the sensing elements to eliminate errors that are catastrophic, this isn’t always enough. Sometimes, water accumulates.

When water accumulates, it does so in or on the filter material. When this occurs, it will create a microclimate that surrounds the sensor. This causes measurement errors to occur.


Another way to ensure that you’re measuring humidity accurately in your cleanroom is to choose an RH device that has sensors that are accurate in the way that you need. There are a variety of RH sensors that are available.

No one has established a standard accuracy requirement. So, manufacturers need to consider what specific applications the RH devices will be used for. This way, they can determine what they need in terms of accuracy specifications.

Note that, even though accuracy specifications are important criteria, they shouldn’t necessarily be factors that are decisive for RH instruments. Sometimes, performance claims can be misleading.

This is because, in measurement science, the term “accuracy” is qualitative and includes uncertainty.

Long-Term Stability

Easily, the most important characteristic in terms of performance for a relative humidity instrument is long-term stability. This is the ability of the instrument, over a long time and consistently, to make measurements that are accurate.

Vendors that are reputable will perform tests that are long-term so that they can characterize the devices they sell.

By looking at the results of these long-term tests, personnel will get some help in understanding the baseline performance of the sensors. However, the performance might not be the same as it would be in a clean room.

This is because individual cleanrooms have unique conditions.


One of the greatest threats to an RH instrument’s long-term stability in a cleanroom is the vapor, as well as the chemicals that are utilized in cleanroom processes. In high-humidity conditions, vapors cause RH readings to be incorrectly low.

On the other hand, in conditions that have low humidity, vapors cause RH readings to be incorrectly high.

It’s important to note that some RH devices have features that will minimize chemical effects. For example, an RH device might have a chemical-purge function.

How to Ensure the Accuracy of the Measurement of Temperature

Because it’s so important to track the environment of a cleanroom, you must ensure that the measurement of temperature is accurate. A humidity and temperature monitor for your cleanroom can help with this. However, how can you ensure its measurements are as accurate as possible?

Regulation Compliance

DIN EN ISO 14644-3 requires that a cleanroom’s ventilation system be able to undergo testing so that the tests show that the environment meets the relative humidity and temperature requirements for the cleanroom.

This is because temperature and humidity can have certain impacts on some processes in the cleanroom.

They can influence rust formation and corrosion, the growth and disintegration of micro-organisms, and the hardening or expansion of materials. These can all potentially damage the products you’re manufacturing in the cleanroom.

For this reason, you must find a humidity and temperature monitor that has highly accurate probes.

Additionally, these highly accurate probes must be able to measure temperature accurately enough to meet regulatory compliance requirements. So, when looking for the right system, ensure it has these probes.

Also, look for a guarantee from the company that its highly accurate probes make it possible for you to have a regulation-compliant temperature (as well as air humidity) in your cleanroom.

High Accuracy Level

Something else you should look for is a guarantee of a high accuracy level from the company you buy your humidity and temperature monitor from. This is a high accuracy level directly related to the measuring instruments as outlined in DIN EN ISO 7726.

Look for a product that has high accuracy levels that follow the requirements of DIN EN ISO 7726. This way, you can ensure that the readings are accurate according to this standard.

This will have two benefits. First of all, it will help you to ensure that your cleanroom environment is appropriate. This, in turn, will help you avoid problems with what you’re creating in your cleanroom.

Second, this will help you ensure that you’re following regulations. This will protect you legally.

Uninterrupted Readings

Whether you’re planning on using a medical temperature monitor or another type of temperature monitor in your cleanroom, one of the features you need to look for in a humidity and temperature monitor is uninterrupted readings.

This way, you can ensure that when you’re getting the readings, they’re as accurate as possible to reflect the most recent temperature. Additionally, the more constant the readings are, the sooner issues can be addressed.

This will provide you with peace of mind, as you can feel sure that your cleanroom has the correct temperature at nearly all times. Additionally, there’s the benefit that you’ll be following through with compliance requirements.

Long-Term Stability

Like with relative humidity, long-term stability is also important for temperature monitoring. If the instruments are not reliable, then two problems can potentially occur. First, they could degrade over time and provide measurements that are not accurate.

If this were to happen, you could end up having problems in your cleanroom, such as ruined products. Additionally, if the instruments don’t have long-term stability, this means you’d have to replace them.

Automated Notifications

Another important feature when you’re using a healthcare temperature monitoring system or another type of temperature monitoring system is automated notifications. This goes hand-in-hand with the uninterrupted readings we covered above.

While uninterrupted readings are useful, they won’t be of much use if you don’t get alerted when the temperature has shifted too much in one direction or another. This is because you won’t receive accurate readings until it’s too late.

With automated notifications, on the other hand, you’ll be alerted immediately if there’s a temperature problem. As a result, you’ll be able to take timely, effective action before there is a breach of unacceptable thresholds.

This will allow your staff to prevent damage that’s irreversible to the quality of work and product integrity.

Looking for a Humidity and Temperature Monitor?

Now that you’ve learned how to ensure that a humidity and temperature monitor has accurate readings, you might be looking for one that will give you accurate readings you can use within your cleanroom. In this case, look no further than SensoScientific.

At SensoScientific, we offer many products for measuring temperature and humidity.

We also offer products that measure differential pressure, oxygen, carbon dioxide, water leaks, and more. To learn more about our products, check them out now.

Newsletter Signup - Downloadable Content

Signup for our newsletter to proceed to download.