Humidity In Clean Rooms

Humidity In Clean Rooms

Clean Rooms In General

A clean room is a manufacturing environment that has a low level of environmental pollutants such as dust, airborne microbes, aerosol particles and chemical vapors. The air inside is constantly recirculated through High Efficiency Particulate Air (HEPA) filters. Some clean rooms are entire manufacturing facilities and can cover thousands of square meters.

Clean rooms are used extensively by semiconductor manufactures. Today, more and more biotechnology, life sciences and other fields that are sensitive to environmental contamination also use clean rooms.

Clean rooms are classified according to the number and size of particles permitted per volume of air. Nowadays the ISO 14644-1 is the official metric standard, which specifies the number of particles (0.1 µm or larger) permitted per cubic meter of air.

The previous standard FED STD 209E was used up to 2001 and indicated the maximum of particles (0.5µm or larger) permitted per cubic foot of air.

Both standards, old and new, assume relationships between particle size and particle concentration.

Why the Need to Measure Humidity?

Clean rooms are used in various industries: pharmaceutical, semiconductor, aerospace, food, laser and optic…

Many different parameters are measured (particles, air flow, pressure…). The effects caused by humidity can be expansion, contraction, hardening and softening of materials, viscosity change of liquid, growth of microbes, increase in static electricity, corrosion and rust.

All applications have different specifications for temperature and humidity. An abnormal level of these parameters can have a significant impact on product quality and production efficiency (perhaps even loss of production).

High humidity and/or temperate can cause some instruments go out of specification.

Low humidity can generate static electricity which can then destroy the production batch as well as expensive measurement equipment.

Pharmaceutical manufactures control and record temperature and humidity according to GMP and internal quality guidelines.

The semiconductor and electronics manufacturing process require vary accurate control in their clean rooms.

In the food industry it is important that the relative humidity stays under 40%: this restricting growth of bacteria and germs.

What solution can Rotronic offer?

In a clean room, it is important that there be as fewer places possible where dust can collect. As most transmitters could be a possible collection point, it would be best to have the probe remote to the transmitter and the transmitter installed outside the clean room.

As the entire Rotronic product range offers probe interchangeability, it is possible to place an extension cable between both the probe and transmitter.

Extension possibilities:

  • 1,2 or 5 meters.
  • Up to 100 meters with the signal booster.

Rotronic Products:

Humidity and temperature probes:

  • HC2-IS25
  • HC2-IT25
    -40…85°C,0…100%rh,Ø26mm,±1.5%rh and ±0.1K…
  • HC2-S-50…100°C,0…100%rh,Ø15mm,±0.8%rh and ±0.1K…
  • HC2-IM102-100…200°C,0…100%rh,Ø15mm,±0.8%rh and ±0.1K…


  • HF5 series

For interchangeable probes, 2 or 3/4 wire configuration, Various analogue and digital outputs, Display, All psychrometic calculations available…

  • HF8 series

Two Interchangeable probes
-100…200°C, 3/4 wire configuration, Various analogue outputs, Relay and data logging All psychrometic calculations Display…

Filters and pore size:

  • Polyethylene grey 20μm
  • Polyethylene white 40μ
  • Wire-mesh 20…25μm
  • Teflon 10μm
  • MFD (fleece)
  • Polypropylene 150μm

Protection caps

  • Protection-HC2
  • Protection-Filter
  • Protection E2/E3

Customer Benefits:


A precise humidity measurement has direct influence to the energy consumption of a clean room. The sooner any power consuming unit is switching off, the less power will be consumed.

The better the environment is controlled the less the deviation in product quality. The consequence will be lesser deviation in result of bioassays, less deviation in integrated circuited manufacturing and in food production less growth of microbes. The outstanding accuracy and long-term stability of our probes does ensure a constant and stable environment that is directly linked to the product quality.

The HC2-IT25 & HS2-IS25 Probes:

The button probes are designed for integration into walls, collect hardly any dust and are easy to clean.

The HC2-IT25 is delivered with a Teflon filter whereas HC2-IS25 comes with a steel sinter filter. Both are delivered with a protection cap that come useful when the clean room undergoes cleaning.

Other protection caps:

We, offer for the HC2 probes, two different protection caps. The red “protection-filter” cap replaces the HC2 filter.

The transparent “protection-HC2” can be used for all 15mm probes. To protect the probe connector we also offer a transparent cap: the “protection E2/E3”.

Source: Rotronic

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