Humidity Indicator Description

Humidity Indicators indicate or quantify relative humidity levels. At Stratotech, we offer a variety of high quality humidity indicator plugs & cards for use in both shipping containers as well as in other applications.

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Humidity Indicators

Humidity indicators are a low-cost method for tracking humidity levels. Typically, they are used on moisture controlled enclosures such as rigid shipping containers, refrigerators, optical cavities, electronic enclosures, and vacuum packaging to monitor and provide visual proof of the relative humidity level inside. When a change is detected, the colour on the indicator changes, indicating high and low levels. This way, moisture levels inside a controlled space can be closely and continually monitored to protect the contents from potential damage. There are 2 types of humidity indicators:

  1. Indicator cards
  2. Indicator plugs

What are humidity indicator cards, and how do they work?

These are moisture sensitive papers designed to change colour when an indicated level of humidity is exceeded inside a controlled space. They usually are impregnated with desiccants such as copper chloride, urea, methylene blue, cobalt chloride, or CoCl2-SiO2. These chemicals easily detect humidity changes. When humidity increases, the colour on the indicator dots changes from blue through various shades of magenta – red, to pink, and reverses back to blue when it decreases.

What are Humidity indicator plugs how do they work? 

Humidity indicator plugs are moisture measuring instruments externally screwed on reusable or long-term storage enclosures such as closed packages or shipping containers. Unlike humidity indicator cards, they are designed with clear glass indicator discs which allow you to monitor relative humidity levels inside the controlled space without having to open it.

Things to avoid when using humidity indicators

  • Indicator cards should never be placed near steam, water or be exposed to high humidity levels for a long time since the chemicals used in these indicators are water-soluble so.  
  • Moreover, solvents such as ammonia can bleach the indicator dye, and this can potentially damage their colour reversibility feature 

How to choose the right humidity indicator

Your decision largely depends on the type of goods, the ideal level of humidity they can handle, and the nature of the storage space you want to monitor. All in all, this boils down to your needs and preferences.

  1. AccuracyIf you are monitoring products that are highly susceptible to moisture, go for high sensitivity Indicators with a manganese-based desiccant. They are also cobalt-free and can be used for virtually any application.
  2. CapacitySpaces with high amounts of water require indicators with a PH-sensitive desiccant such as CuCl2/Silica Gel. This can detect high amounts of moisture from water leaks.
  3. UseIndicator plugs best monitor rigid containers since these can be mounted on the walls and readings can be made without opening them. For packing, an indicator card will come in handy.
  4. Reliability: If you want to use for a short period, an irreversible one is ideal, but if you are looking for an indicator you can use for a long time, go for a reversible one since it works like a thermometer fluctuating with humidity changes.  

Humidity indicators we offer at Stratotech

At Stratotech, we offer a variety of high-quality humidity indicators for virtually any application. They are also designed with different materials and calibrations to fit your needs and preferences and are all compliant with quality control standards. We have both indicator plugs and indicator cards.

Indicator cards 

We have two types of indicator cards, and these are designed with different sensitivity levels to cater for all of your needs.

  1. Reversible indicator cards can be used to establish if a desiccant is working
  2. Maximum indicator cards show the highest level of humidity experienced in the storage space.  

Indicator plugs

Our collection of indicator plugs is also comprehensive. They are crafted from aluminum and brass plus you have several two mounting diameters (1.00 inch or Less and 1.01 – 2.00 inches) and three housing materials (Anodized, zinc plated and Black Anodized) to choose from.