Indoor Humidity Guidelines

Summary

40-60%RH is ideal

Most professional bodies from around the world agree 40-60%RH is optimal for health.

Humidity impacts health

Guidelines highlight the negative impact to health of excessively low or high humidity.

Control humidity

Using humidity control systems, set to 40-60%RH, is important for proper environmental control.

What is the recommended indoor humidity level?

The recommended relative humidity for both homes and workplaces is between 40% and 60%. Maintaining humidity within this range helps create a healthy and comfortable indoor environment by preventing the air from becoming either too dry or too humid. If humidity levels fall outside this range for extended periods, it can have a negative impact on both comfort and overall wellbeing.

Many people mistakenly believe that indoor climate problems are primarily caused by excessive humidity, leading to mould and condensation. In reality, for a large part of the year, indoor air is often too dry. Low humidity is a common cause of indoor air quality issues and can contribute to dry skin, irritated eyes and airways, increased susceptibility to viruses, and discomfort for building occupants.

Good to know about indoor air quality and humidity

Indoor air is too dry for more than half of the hours in a typical year.

Take our indoor climate test to find out if you have symptoms caused by low humidity.

Condensation and mould growth generally occur only when the relative humidity in a room exceeds 80%.

We recommend maintaining a relative humidity between 40% and 60% for a healthy and comfortable indoor environment.

Maintaining the recommended humidity range can significantly reduce the survival of airborne viruses. This is one reason why respiratory infections are more common during the winter months, when indoor air is typically much drier.

How can you prevent dry indoor air?

Many common recommendations for increasing indoor humidity have only a limited effect. You may have heard suggestions such as:

Adding more indoor plants
Ventilating regularly by opening windows
Installing indoor water features

While these measures can increase humidity slightly, they are generally not sufficient to maintain the recommended indoor humidity level.

Plants naturally release moisture into the air through transpiration, but even a large number of plants will have only a modest impact on the humidity in a typical home or office.

Regular ventilation is important for maintaining good indoor air quality. It helps reduce carbon dioxide (CO₂), remove indoor pollutants and provide fresh air. However, during much of the year, outdoor air contains very little moisture. As this dry air is brought indoors and heated, the relative humidity drops even further, often resulting in excessively dry indoor conditions.

Where consistent humidity levels are required, a dedicated humidification system is the most effective way to maintain the recommended relative humidity of 40–60% throughout the year.

How to maintain the right humidity and a healthy indoor climate

The easiest way to monitor indoor humidity is to use a hygrometer. Measuring the relative humidity allows you to ensure it remains within the recommended range of 40–60% RH, helping to create a healthy and comfortable indoor environment.

Everyday activities can temporarily increase indoor humidity, for example:

Boiling water in a kettle
Leaving the bathroom door open after showering
Cooking without using a lid
Drying laundry indoors

While these activities release moisture into the air, they typically have only a short-term effect and are not sufficient to maintain a consistent humidity level.

Monitor your indoor humidity

Indoor humidity naturally varies throughout the year. During the warmer months, outdoor air generally contains more moisture, and additional humidification is often unnecessary. In some situations, excess humidity may even require dehumidification.

Most indoor air quality problems related to humidity occur during the heating season, when cold outdoor air is heated indoors and the relative humidity drops significantly. This is when humidification is often needed to maintain a healthy indoor environment.

Monitoring humidity with a hygrometer is the best place to start. Regular measurements provide valuable insight into your indoor climate and help determine whether humidification or dehumidification is required to maintain optimal conditions.

Maintaining the right indoor humidity can be confusing, especially as much of the advice available online is either oversimplified or misleading. Many suggested methods have only a temporary or negligible impact on humidity levels and are often aimed at protecting buildings rather than creating a healthy indoor environment for people.

Where consistent humidity control is required, a dedicated humidification system is the most effective solution. Modern hygienic humidifiers operate automatically, continuously monitoring and adjusting humidity levels to maintain the recommended range of 40–60% RH. This helps create a healthier, more comfortable indoor environment while avoiding both excessively dry and overly humid conditions.

Industry guidelines and regulations on indoor humidity

Information package: In-room humidification

Always the right fit – find out more here!

In-room humidifiers are used specifically where humidity is required. Suitable for every application and room size, ideal for retrofitting, energy-efficient and easy to maintain.

Request your free information package here and get a free thermo-hygrometer to measure your humidity!

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