Air Humidification in Hospitals – essential for patient wellbeing, operational reliability and cost efficiency

Why is professional air humidification in hospitals important, and what is it used for? Discover how optimal humidity levels help to reduce infections, protect expensive medical equipment, and ensure reliable planning. Today, air humidification systems are an integral part of modern building services engineering—particularly in hygiene-sensitive environments such as hospitals, medical laboratories and research facilities. For building planners and hospital operators, they represent a critical interface between hygiene, energy efficiency, operational reliability and regulatory compliance.

The optimal range is 40–60% relative humidity

As numerous studies and standards indicate, the optimal range is between 40–60% relative humidity. But why exactly does the ideal humidity level fall within this range, and what does this mean in practice for the planning and operation of a hospital?

The following seven points provide an initial overview and offer clear answers.

1. Optimal humidity as a key factor in reducing hospital-acquired infections

✅ Targeted control of airborne infections

Relative humidity has a direct impact on the behaviour of infectious aerosols:

- < 40% RH → aerosols shrink, remain airborne for longer → higher risk of infection
- 40–60% RH → droplets settle more quickly → reduced transmission

Planning implication: Humidity is a controllable parameter for infection control—not merely a comfort factor.

✅ Impact on patient health

The right level of humidity also supports the body’s natural defence mechanisms:

- Stabilisation of mucous membranes
- Maintenance of mucociliary clearance
- Improved defence against inhaled pathogens

Planning implication: Humidity has a direct influence on treatment quality and patient safety.

Figure 1: High transmissibility at RH < 40%

Figure 2: Significantly reduced transmissibility at 40% < RH < 60%

2. Optimal humidity as a factor for operational reliability – protecting medical equipment from ESD damage

An often-underestimated aspect of hospital planning is the impact of dry air on medical equipment and the associated risk of electrostatic discharge (ESD) on the safe operation of a hospital.

In excessively dry environments:

- static electricity builds up
- electrostatic discharges (ESD) occur
- sensitive equipment can be damaged or may deliver inaccurate data

Even low discharge voltages—imperceptible to humans—can lead to equipment failures.

Implication for hospital operators: Uncontrolled humidity can result in unplanned downtime, increased maintenance costs and risks to operational processes.

3. User comfort and performance in hospital operations

How does humidity, beyond medical and technical aspects, also affect staff working conditions and patient comfort?

Excessively dry air has been proven to cause a range of undesirable effects:

- irritation of the eyes and respiratory tract
- dry skin
- reduced concentration
- increased susceptibility to errors

In the long term, this can contribute to so-called Sick Building Syndrome.

Implication for hospital operators: Optimal humidity is a key factor in staff productivity and patient satisfaction.

4. Why is air humidification in hospitals absolutely necessary from a physical perspective? What solutions are available?

The challenge: Fresh air + heating = dry air

In hospital facilities, indoor air must be regularly exchanged to achieve the recommended air quality. During this process, the following occurs:

- cold outside air is heated
- the absolute moisture content remains constant
- the relative humidity drops significantly (e.g. to approx. 12%)

Without active humidification, excessively dry air is inevitably created—particularly during winter operation.

The solution: Integration of humidification systems

To achieve target humidity levels, mechanical humidification systems are essential. Broadly speaking, two different technologies or methods are available for this purpose:

Isothermal humidification (steam)

✅ very high level of hygiene safety

✅ often required (e.g. in operating theatres)

✅ high degree of flexibility in adaptation

Learn more about isothermal systems

Adiabatic humidification (atomisation)

✅ very energy-efficient

✅ suitable for handling large volumes of air

✅ potential additional cooling effect

Learn more about adiabatic systems

5. Planning criteria for humidification systems in hospitals

The points outlined above leave no doubt that when planning an HVAC system (air handling unit system) as part of a new build or the modernisation of a hospital, air humidification must be considered and incorporated from the outset. What requirements and planning criteria arise for building services engineers and operators when designing humidification systems?

Hygiene safety (top priority)

✅ prevention of Legionella growth

✅ use of germ-free methods (e.g. steam humidification)

✅ water treatment (e.g. reverse osmosis)

Reliability in 24/7 operation

✅ continuous humidity control

✅ redundancy concepts

✅ minimised maintenance downtime

Energy efficiency and operating costs

✅ adiabatic systems with low energy consumption

✅ use of evaporative cooling

✅ optimisation of overall energy efficiency

Integration into building management systems (BMS)

✅ monitoring and control of central systems

✅ integration via standard protocols (e.g. BACnet, Modbus)

✅ remote monitoring and data analysis

We have provided many additional resources for the professional planning of air humidification in HVAC (AHU) systems in our HY Planners' Guide. Would you like to have the key information on air humidification quickly and clearly at your fingertips? Then download the HumiGuide app free of charge.

6. Which standards and regulatory requirements govern the planning of air humidification in hospital HVAC systems?

Air humidification in hospitals is clearly regulated. Particularly relevant standards include DIN 1946-4 and VDI 6022. These set out key planning requirements, including:

- temperature and humidity ranges
- air change rates
- filtration and hygiene standards
- airflow design

Additional, more stringent regulations apply to highly hygiene-sensitive areas such as operating theatres. In such environments, only isothermal humidification systems are often permitted.

Conclusion: In hospitals, air humidification is not an optional feature, but an integral part of compliant and regulation-driven system design.

7. The cost efficiency of humidification systems: what impact does humidification have on operational costs and the healthcare system?

Hospital-acquired infections result in significant costs:

‼️ extended patient stays
‼️ additional treatments
‼️ legal risks

An optimised humidity level can:

✅ reduce infection rates
✅ lower operational costs
✅ improve overall cost efficiency

Conclusion for planners and hospital operators
regarding air humidification

Air humidification in hospitals is a key parameter for:

- infection prevention
- operational reliability of medical equipment
- energy efficiency and cost reduction
- regulatory compliance and future-proofing

The target range of 40–60% relative humidity brings together all requirements in a technically sound optimum.

Practical conclusion:
Humidification must be considered at an early planning stage and consistently integrated into operations – as an integral part of hospital infrastructure.

For further information, please do not hesitate to contact us.
We will be pleased to advise you.

You can find the detailed white paper on the topic of ‘Air humidification in hospitals’, which includes numerous links, sources and studies, here: