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What Does “Rh” Mean on a Dehumidifier?

Dehumidifier With Touch Panel

Dehumidifiers have become more common in recent years for a variety of applications. These include allergy relief, hygiene, and home repair after flooding. On them are several measurements and indicators, one of which is Rh.

This abbreviation isn’t very descriptive, which might make you wonder what this means.


Rh stands for Relative Humidity. Relative Humidity is a comparison between the current moisture in the air and the maximum amount of moisture the air can hold at the current temperature.

This is a different measurement and Absolute Humidity, which doesn’t depend on the current temperature.

For a more detailed definition of Rh and some reasons, it is more useful than Ah. Read on!

Defining Relative Humidity

The relative humidity tells you what the humidity is compared to what the maximum is (at that temperature). Warmer air can hold more moisture, meaning that an Rh of 50% in warm environments is very different from an Rh of 50% in a cold environment.

This differs from Ah (absolute humidity), which would give the same humidity measurement in both a cold and a warm environment.

2 Ways To Use Rh Readings

The Rh reading on your dehumidifier is the most useful reading on the machine.

1. Prevent Condensation

Window With Condensation

The Ah level that will produce condensation differs in hot and cold temperatures. Therefore, Rh is more useful in preventing condensation. You want to aim for an Rh level of 30% to 40% to avoid condensation in your home.

2. Prevent Bacteria, Mold, and Dust Mites

Strong Mildew In Large Stains

Rh is also much more useful than Ah for preventing the growth of undesirable organisms. This is because how easily bacteria, mites, and mold grows changes depending on temperature, which in turn changes their moisture requirements.

To get the most mold-busting power out of your dehumidifier, keep the Rh level below 50%. This might feel dry in the colder months but will lead to a cleaner house in the long run.

What To Do if Your Humidifier Doesn’t Measure Rh

Despite it being the most effective measurement of humidity for consumers, not all dehumidifiers measure Rh. If you have a unit that doesn’t measure Rh, you can buy a separate hygrometer to do so.

Sadly, there’s no way to integrate this hygrometer with the existing dehumidifier. Still, you can manually adjust the humidifier’s settings until you get the reading that you want on the hygrometer. This may take some trial and error, but you will quickly understand how the dehumidifier affects the readings.


Modern Technology Dehumidifier

Rh (Relative Humidity) refers to the amount of moisture in the air relative to the maximum amount of moisture air at that temperature can hold. This makes it more useful for assessing the effect of humidity on living organisms such as mites, mold, and bacteria. It also is more effective at predicting the amount of condensation.

Frequently Asked Questions

What Is the Best Setting for My Dehumidifier?

In most cases, a dehumidifier should be set between 30% and 60%. This number should go down to 40% maximum in the heating months.

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