Humidity Sensors for Swimming Pools and Spa Areas

July 14, 2026

In our previous article, we described the specific challenges that high humidity, condensation, and harsh environmental conditions pose for modern sensor technology. That article highlighted just how significantly external factors can affect the measurement stability and service life of sensors.

Swimming pools and similar environments represent a particularly challenging application area. In addition to consistently high humidity, chemical stresses also directly affect the sensors used in these settings.

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In a nutshell

In swimming pools, wellness areas, and similar humid environments, high humidity, warm indoor air, chlorine, and aerosols all come together. This combination places high demands on humidity and temperature measurement—especially when sensors are required to provide stable, long-term readings for ventilation, dehumidification, and indoor climate control.

The AFTF-45 and KFTF-45 are designed for harsh environmental conditions and support reliable measurement in contaminated ambient air.

Typical benefits:

Stable readings even under conditions of high humidity and chemical exposure
PTFE-protected sensors for harsh environments
Suitable for indoor swimming pools, wellness areas, mechanical rooms, and air ducts
Support for Ventilation, Dehumidification, and Climate Control
Integration via 0–10 V or 4–20 mA into building management systems (BMS), DDC, or HVAC systems

Use in Swimming Pools and Wellness Areas

Swimming pools and wellness areas present challenging conditions for humidity and temperature sensors. In addition to consistently high humidity, warm indoor air, chlorine compounds, and moist aerosols also affect the sensors in use. Particularly in indoor swimming pools, locker rooms, utility rooms, or air ducts, these conditions can compromise the long-term stability of conventional humidity sensors.

Typical applications include:

Indoor swimming pools
Wellness and Spa Areas
Changing and shower areas
Utility rooms with humid or contaminated air
Supply and exhaust air ducts for HVAC systems

For operators, this means that humidity measurement must not only detect high relative humidity but also function reliably in environments with chemical contamination. This is the only way to ensure that ventilation, dehumidification, and indoor climate can be regulated in a consistently stable manner.

Why Traditional Humidity Sensors Have Their Limitations in Swimming Pools

Conventional humidity sensors are often not designed to withstand the continuous exposure to ambient air in such environments. In swimming pools, several factors come into play: high humidity, warm air, chlorine compounds, aerosols, and deposits from the ambient air.

Over time, these stresses can affect the sensor element or alter the sensor layer. This often results in gradual changes: measured values respond more slowly, deviate more significantly, or can no longer be reliably reproduced.

This is particularly critical in indoor climate control. If humidity levels are no longer reliable, the building management system (BMS) or distributed control system (DDC) can no longer optimally control dehumidification, ventilation, or heat recovery. This can lead to unnecessary energy consumption, unstable indoor conditions, or increased maintenance requirements.

Typical challenges: chlorine, aerosols, and high humidity

The most challenging conditions in a swimming pool are not caused by humidity alone, but by the combination of humidity and chemical exposure.

Typical influencing factors include:

Chlorine pollution: Chlorine-containing substances in the air can cause long-term damage to the sensors.
Aerosols: Fine water droplets and airborne particles can settle on surfaces.
Warm, humid air: High relative humidity and elevated temperatures accelerate degradation processes.
Airflow: Supply and exhaust air, recirculation systems, and dehumidification affect the local humidity distribution.
Cleaning and Spray Mist: Cleaning processes or wet surfaces can cause localized moisture spikes.

This is exactly where the AFTF-45 and KFTF-45 come into play: The PTFE-protected sensor technology reduces the direct impact of harsh ambient air on the sensor element, thereby ensuring more stable measurements over longer periods of time.

What metrics are relevant for a swimming pool?

Humidity and temperature are key parameters for regulating swimming pool and wellness areas. Their interaction is particularly important: Warm air can hold more Humidity; as the air cools, relative humidity rises rapidly, and the risk of condensation increases.

Key metrics include:

Relative humidity—a key control variable for indoor climate and dehumidification
Temperature – affects comfort, humidity behavior, and control strategy
Dew Point – Helps Assess Condensation Risks
Absolute humidity – indicates the actual water content of the air
Mixing ratio – aids in the evaluation of ventilation and dehumidification processes

The AFTF-45 and KFTF-45 measure humidity and temperature and can provide additional calculated parameters for building management systems (BMS), distributed control systems (DCS), programmable logic controllers (PLCs), or ventilation systems.

AFTF-45 or KFTF-45—which model is right for you?

For swimming pools and wellness areas, both surface-mounted sensors and duct sensors may be suitable, depending on the facility. The key factor is where the measured value is needed for control or monitoring.

AFTF-45 as a surface-mounted sensor

Wall mounting in swimming pools, wellness areas, or utility rooms
Direct measurement of indoor air
Suitable for areas with humid and contaminated ambient air

The AFTF-45 is suitable for situations where humidity and temperature need to be measured directly in the room—for example, in indoor swimming pools, shower areas, locker rooms, or adjacent utility areas.

KFTF-45 as a duct sensor

Installation in ventilation and air conditioning ducts
Measurements in Supply or Exhaust Air Ducts
Suitable for HVAC systems, recirculating air systems, and central dehumidification

The KFTF-45 is useful when humidity and temperature need to be measured in the air duct, for example, to control exhaust air, supply air, dehumidification, or heat recovery.

In larger swimming pool facilities, a combination of the two may be useful: The room sensor monitors conditions in the lounge area, while the duct sensor monitors which air is being exhausted, treated, or recirculated.

Differences: AFTF-35 vs. AFTF-45

The AFTF-35 and KFTF-35 are the right choice when high humidity and the risk of condensation are primary concerns.

AFTF-45 and KFTF-45 are useful when additional chemical or particulate contamination is present—for example, from chlorine, aerosols, cleaning residues, or contaminated ambient air.

As a simple guide to help you decide:

Condensation and moisture dynamics are the main problem: Series 35
Chlorine, aerosols, or contaminated air are the main problem: Series 45

Click here for our blog post for high-moisture applications (AFTF-35 / KFTF-35)

Choose the right humidity sensors for your pool and spa now

In swimming pools and wellness areas, high humidity, warm indoor air, chlorine exposure, and aerosols place special demands on sensor technology. The AFTF-45 and KFTF-45 are designed for harsh environmental conditions and ensure stable humidity and temperature measurements in contaminated ambient air.

For you, this means:

More reliable measurements in demanding swimming pool environments
a better foundation for ventilation, dehumidification, and climate control
less maintenance and replacement work
Easy integration into building management systems, DDC, PLCs, or HVAC systems
Suitable designs for in-room and duct measurements

Depending on the installation situation, choose the appropriate model: AFTF-45 for direct indoor air measurement or KFTF-45 for installation in ventilation and HVAC ducts.

Discover Humidity Sensors for Swimming Pools & Spas